1 // Formatting top-level items - functions, structs, enums, traits, impls.
4 use std::cmp::{max, min, Ordering};
8 use rustc_ast::{ast, ptr};
9 use rustc_span::{symbol, BytePos, Span, DUMMY_SP};
11 use crate::attr::filter_inline_attrs;
13 combine_strs_with_missing_comments, contains_comment, is_last_comment_block,
14 recover_comment_removed, recover_missing_comment_in_span, rewrite_missing_comment,
17 use crate::config::lists::*;
18 use crate::config::{BraceStyle, Config, IndentStyle, Version};
20 is_empty_block, is_simple_block_stmt, rewrite_assign_rhs, rewrite_assign_rhs_with,
21 rewrite_assign_rhs_with_comments, RhsAssignKind, RhsTactics,
23 use crate::lists::{definitive_tactic, itemize_list, write_list, ListFormatting, Separator};
24 use crate::macros::{rewrite_macro, MacroPosition};
26 use crate::rewrite::{Rewrite, RewriteContext};
27 use crate::shape::{Indent, Shape};
28 use crate::source_map::{LineRangeUtils, SpanUtils};
29 use crate::spanned::Spanned;
30 use crate::stmt::Stmt;
31 use crate::types::opaque_ty;
33 use crate::vertical::rewrite_with_alignment;
34 use crate::visitor::FmtVisitor;
36 const DEFAULT_VISIBILITY: ast::Visibility = ast::Visibility {
37 kind: ast::VisibilityKind::Inherited,
42 fn type_annotation_separator(config: &Config) -> &str {
46 // Statements of the form
47 // let pat: ty = init;
48 impl Rewrite for ast::Local {
49 fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
51 "Local::rewrite {:?} {} {:?}",
52 self, shape.width, shape.indent
55 skip_out_of_file_lines_range!(context, self.span);
57 if contains_skip(&self.attrs) || matches!(self.kind, ast::LocalKind::InitElse(..)) {
61 let attrs_str = self.attrs.rewrite(context, shape)?;
62 let mut result = if attrs_str.is_empty() {
65 combine_strs_with_missing_comments(
70 self.attrs.last().map(|a| a.span.hi()).unwrap(),
79 let pat_shape = shape.offset_left(4)?;
81 let pat_shape = pat_shape.sub_width(1)?;
82 let pat_str = self.pat.rewrite(context, pat_shape)?;
83 result.push_str(&pat_str);
85 // String that is placed within the assignment pattern and expression.
87 let mut infix = String::with_capacity(32);
89 if let Some(ref ty) = self.ty {
90 let separator = type_annotation_separator(context.config);
91 let ty_shape = if pat_str.contains('\n') {
92 shape.with_max_width(context.config)
96 .offset_left(last_line_width(&result) + separator.len())?
100 let rewrite = ty.rewrite(context, ty_shape)?;
102 infix.push_str(separator);
103 infix.push_str(&rewrite);
106 if self.kind.init().is_some() {
107 infix.push_str(" =");
113 result.push_str(&infix);
115 if let Some((init, _els)) = self.kind.init_else_opt() {
116 // 1 = trailing semicolon;
117 let nested_shape = shape.sub_width(1)?;
119 result = rewrite_assign_rhs(
123 &RhsAssignKind::Expr(&init.kind, init.span),
134 // FIXME convert to using rewrite style rather than visitor
135 // FIXME format modules in this style
139 unsafety: ast::Unsafe,
140 abi: Cow<'static, str>,
141 vis: Option<&'a ast::Visibility>,
142 body: Vec<BodyElement<'a>>,
147 fn from_foreign_mod(fm: &'a ast::ForeignMod, span: Span, config: &Config) -> Item<'a> {
149 unsafety: fm.unsafety,
151 ast::Extern::from_abi(fm.abi),
152 config.force_explicit_abi(),
159 .map(|i| BodyElement::ForeignItem(i))
167 enum BodyElement<'a> {
168 // Stmt(&'a ast::Stmt),
169 // Field(&'a ast::ExprField),
170 // Variant(&'a ast::Variant),
171 // Item(&'a ast::Item),
172 ForeignItem(&'a ast::ForeignItem),
175 /// Represents a fn's signature.
176 pub(crate) struct FnSig<'a> {
177 decl: &'a ast::FnDecl,
178 generics: &'a ast::Generics,
180 is_async: Cow<'a, ast::Async>,
181 constness: ast::Const,
182 defaultness: ast::Defaultness,
183 unsafety: ast::Unsafe,
184 visibility: &'a ast::Visibility,
188 pub(crate) fn from_method_sig(
189 method_sig: &'a ast::FnSig,
190 generics: &'a ast::Generics,
191 visibility: &'a ast::Visibility,
194 unsafety: method_sig.header.unsafety,
195 is_async: Cow::Borrowed(&method_sig.header.asyncness),
196 constness: method_sig.header.constness,
197 defaultness: ast::Defaultness::Final,
198 ext: method_sig.header.ext,
199 decl: &*method_sig.decl,
205 pub(crate) fn from_fn_kind(
206 fn_kind: &'a visit::FnKind<'_>,
207 generics: &'a ast::Generics,
208 decl: &'a ast::FnDecl,
209 defaultness: ast::Defaultness,
212 visit::FnKind::Fn(fn_ctxt, _, fn_sig, vis, _) => match fn_ctxt {
213 visit::FnCtxt::Assoc(..) => {
214 let mut fn_sig = FnSig::from_method_sig(fn_sig, generics, vis);
215 fn_sig.defaultness = defaultness;
221 ext: fn_sig.header.ext,
222 constness: fn_sig.header.constness,
223 is_async: Cow::Borrowed(&fn_sig.header.asyncness),
225 unsafety: fn_sig.header.unsafety,
233 fn to_str(&self, context: &RewriteContext<'_>) -> String {
234 let mut result = String::with_capacity(128);
235 // Vis defaultness constness unsafety abi.
236 result.push_str(&*format_visibility(context, self.visibility));
237 result.push_str(format_defaultness(self.defaultness));
238 result.push_str(format_constness(self.constness));
239 result.push_str(format_async(&self.is_async));
240 result.push_str(format_unsafety(self.unsafety));
241 result.push_str(&format_extern(
243 context.config.force_explicit_abi(),
250 impl<'a> FmtVisitor<'a> {
251 fn format_item(&mut self, item: &Item<'_>) {
252 self.buffer.push_str(format_unsafety(item.unsafety));
253 self.buffer.push_str(&item.abi);
255 let snippet = self.snippet(item.span);
256 let brace_pos = snippet.find_uncommented("{").unwrap();
259 if !item.body.is_empty() || contains_comment(&snippet[brace_pos..]) {
260 // FIXME: this skips comments between the extern keyword and the opening
262 self.last_pos = item.span.lo() + BytePos(brace_pos as u32 + 1);
263 self.block_indent = self.block_indent.block_indent(self.config);
265 if !item.body.is_empty() {
266 for item in &item.body {
267 self.format_body_element(item);
271 self.format_missing_no_indent(item.span.hi() - BytePos(1));
272 self.block_indent = self.block_indent.block_unindent(self.config);
273 let indent_str = self.block_indent.to_string(self.config);
274 self.push_str(&indent_str);
278 self.last_pos = item.span.hi();
281 fn format_body_element(&mut self, element: &BodyElement<'_>) {
283 BodyElement::ForeignItem(item) => self.format_foreign_item(item),
287 pub(crate) fn format_foreign_mod(&mut self, fm: &ast::ForeignMod, span: Span) {
288 let item = Item::from_foreign_mod(fm, span, self.config);
289 self.format_item(&item);
292 fn format_foreign_item(&mut self, item: &ast::ForeignItem) {
293 let rewrite = item.rewrite(&self.get_context(), self.shape());
294 let hi = item.span.hi();
295 let span = if item.attrs.is_empty() {
298 mk_sp(item.attrs[0].span.lo(), hi)
300 self.push_rewrite(span, rewrite);
304 pub(crate) fn rewrite_fn_before_block(
307 ident: symbol::Ident,
310 ) -> Option<(String, FnBraceStyle)> {
311 let context = self.get_context();
313 let mut fn_brace_style = newline_for_brace(self.config, &fn_sig.generics.where_clause);
314 let (result, _, force_newline_brace) =
315 rewrite_fn_base(&context, indent, ident, fn_sig, span, fn_brace_style)?;
318 if self.config.brace_style() == BraceStyle::AlwaysNextLine
319 || force_newline_brace
320 || last_line_width(&result) + 2 > self.shape().width
322 fn_brace_style = FnBraceStyle::NextLine
325 Some((result, fn_brace_style))
328 pub(crate) fn rewrite_required_fn(
331 ident: symbol::Ident,
333 vis: &ast::Visibility,
334 generics: &ast::Generics,
336 ) -> Option<String> {
337 // Drop semicolon or it will be interpreted as comment.
338 let span = mk_sp(span.lo(), span.hi() - BytePos(1));
339 let context = self.get_context();
341 let (mut result, ends_with_comment, _) = rewrite_fn_base(
345 &FnSig::from_method_sig(sig, generics, vis),
350 // If `result` ends with a comment, then remember to add a newline
351 if ends_with_comment {
352 result.push_str(&indent.to_string_with_newline(context.config));
355 // Re-attach semicolon
361 pub(crate) fn single_line_fn(
365 inner_attrs: Option<&[ast::Attribute]>,
366 ) -> Option<String> {
367 if fn_str.contains('\n') || inner_attrs.map_or(false, |a| !a.is_empty()) {
371 let context = self.get_context();
373 if self.config.empty_item_single_line()
374 && is_empty_block(&context, block, None)
375 && self.block_indent.width() + fn_str.len() + 3 <= self.config.max_width()
376 && !last_line_contains_single_line_comment(fn_str)
378 return Some(format!("{} {{}}", fn_str));
381 if !self.config.fn_single_line() || !is_simple_block_stmt(&context, block, None) {
385 let res = Stmt::from_ast_node(block.stmts.first()?, true)
386 .rewrite(&self.get_context(), self.shape())?;
388 let width = self.block_indent.width() + fn_str.len() + res.len() + 5;
389 if !res.contains('\n') && width <= self.config.max_width() {
390 Some(format!("{} {{ {} }}", fn_str, res))
396 pub(crate) fn visit_static(&mut self, static_parts: &StaticParts<'_>) {
397 let rewrite = rewrite_static(&self.get_context(), static_parts, self.block_indent);
398 self.push_rewrite(static_parts.span, rewrite);
401 pub(crate) fn visit_struct(&mut self, struct_parts: &StructParts<'_>) {
402 let is_tuple = match struct_parts.def {
403 ast::VariantData::Tuple(..) => true,
406 let rewrite = format_struct(&self.get_context(), struct_parts, self.block_indent, None)
407 .map(|s| if is_tuple { s + ";" } else { s });
408 self.push_rewrite(struct_parts.span, rewrite);
411 pub(crate) fn visit_enum(
413 ident: symbol::Ident,
414 vis: &ast::Visibility,
415 enum_def: &ast::EnumDef,
416 generics: &ast::Generics,
420 format_header(&self.get_context(), "enum ", ident, vis, self.block_indent);
421 self.push_str(&enum_header);
423 let enum_snippet = self.snippet(span);
424 let brace_pos = enum_snippet.find_uncommented("{").unwrap();
425 let body_start = span.lo() + BytePos(brace_pos as u32 + 1);
426 let generics_str = format_generics(
429 self.config.brace_style(),
430 if enum_def.variants.is_empty() {
431 BracePos::ForceSameLine
436 // make a span that starts right after `enum Foo`
437 mk_sp(ident.span.hi(), body_start),
438 last_line_width(&enum_header),
441 self.push_str(&generics_str);
443 self.last_pos = body_start;
445 match self.format_variant_list(enum_def, body_start, span.hi()) {
446 Some(ref s) if enum_def.variants.is_empty() => self.push_str(s),
448 self.push_rewrite(mk_sp(body_start, span.hi()), rw);
449 self.block_indent = self.block_indent.block_unindent(self.config);
454 // Format the body of an enum definition
455 fn format_variant_list(
457 enum_def: &ast::EnumDef,
460 ) -> Option<String> {
461 if enum_def.variants.is_empty() {
462 let mut buffer = String::with_capacity(128);
464 let span = mk_sp(body_lo, body_hi - BytePos(1));
465 format_empty_struct_or_tuple(
475 let mut result = String::with_capacity(1024);
476 let original_offset = self.block_indent;
477 self.block_indent = self.block_indent.block_indent(self.config);
479 // If enum variants have discriminants, try to vertically align those,
480 // provided the discrims are not shifted too much to the right
481 let align_threshold: usize = self.config.enum_discrim_align_threshold();
482 let discr_ident_lens: Vec<usize> = enum_def
485 .filter(|var| var.disr_expr.is_some())
486 .map(|var| rewrite_ident(&self.get_context(), var.ident).len())
488 // cut the list at the point of longest discrim shorter than the threshold
489 // All of the discrims under the threshold will get padded, and all above - left as is.
490 let pad_discrim_ident_to = *discr_ident_lens
492 .filter(|&l| *l <= align_threshold)
496 let itemize_list_with = |one_line_width: usize| {
498 self.snippet_provider,
499 enum_def.variants.iter(),
503 if !f.attrs.is_empty() {
510 |f| self.format_variant(f, one_line_width, pad_discrim_ident_to),
517 let mut items: Vec<_> = itemize_list_with(self.config.struct_variant_width());
519 // If one of the variants use multiple lines, use multi-lined formatting for all variants.
520 let has_multiline_variant = items.iter().any(|item| item.inner_as_ref().contains('\n'));
521 let has_single_line_variant = items.iter().any(|item| !item.inner_as_ref().contains('\n'));
522 if has_multiline_variant && has_single_line_variant {
523 items = itemize_list_with(0);
526 let shape = self.shape().sub_width(2)?;
527 let fmt = ListFormatting::new(shape, self.config)
528 .trailing_separator(self.config.trailing_comma())
529 .preserve_newline(true);
531 let list = write_list(&items, &fmt)?;
532 result.push_str(&list);
533 result.push_str(&original_offset.to_string_with_newline(self.config));
538 // Variant of an enum.
541 field: &ast::Variant,
542 one_line_width: usize,
543 pad_discrim_ident_to: usize,
544 ) -> Option<String> {
545 if contains_skip(&field.attrs) {
546 let lo = field.attrs[0].span.lo();
547 let span = mk_sp(lo, field.span.hi());
548 return Some(self.snippet(span).to_owned());
551 let context = self.get_context();
553 let shape = self.shape().sub_width(1)?;
554 let attrs_str = field.attrs.rewrite(&context, shape)?;
558 .map_or(field.span.lo(), |attr| attr.span.hi());
559 let span = mk_sp(lo, field.span.lo());
561 let variant_body = match field.data {
562 ast::VariantData::Tuple(..) | ast::VariantData::Struct(..) => format_struct(
564 &StructParts::from_variant(field),
566 Some(one_line_width),
568 ast::VariantData::Unit(..) => rewrite_ident(&context, field.ident).to_owned(),
571 let variant_body = if let Some(ref expr) = field.disr_expr {
572 let lhs = format!("{:1$} =", variant_body, pad_discrim_ident_to);
573 let ex = &*expr.value;
574 rewrite_assign_rhs_with(
579 &RhsAssignKind::Expr(&ex.kind, ex.span),
580 RhsTactics::AllowOverflow,
586 combine_strs_with_missing_comments(&context, &attrs_str, &variant_body, span, shape, false)
589 fn visit_impl_items(&mut self, items: &[ptr::P<ast::AssocItem>]) {
590 if self.get_context().config.reorder_impl_items() {
591 type TyOpt = Option<ptr::P<ast::Ty>>;
592 use crate::ast::AssocItemKind::*;
593 let is_type = |ty: &TyOpt| opaque_ty(ty).is_none();
594 let is_opaque = |ty: &TyOpt| opaque_ty(ty).is_some();
595 let both_type = |l: &TyOpt, r: &TyOpt| is_type(l) && is_type(r);
596 let both_opaque = |l: &TyOpt, r: &TyOpt| is_opaque(l) && is_opaque(r);
597 let need_empty_line = |a: &ast::AssocItemKind, b: &ast::AssocItemKind| match (a, b) {
598 (TyAlias(lty), TyAlias(rty))
599 if both_type(<y.ty, &rty.ty) || both_opaque(<y.ty, &rty.ty) =>
603 (Const(..), Const(..)) => false,
607 // Create visitor for each items, then reorder them.
608 let mut buffer = vec![];
610 self.visit_impl_item(item);
611 buffer.push((self.buffer.clone(), item.clone()));
615 buffer.sort_by(|(_, a), (_, b)| match (&a.kind, &b.kind) {
616 (TyAlias(lty), TyAlias(rty))
617 if both_type(<y.ty, &rty.ty) || both_opaque(<y.ty, &rty.ty) =>
619 a.ident.as_str().cmp(b.ident.as_str())
621 (Const(..), Const(..)) | (MacCall(..), MacCall(..)) => {
622 a.ident.as_str().cmp(b.ident.as_str())
624 (Fn(..), Fn(..)) => a.span.lo().cmp(&b.span.lo()),
625 (TyAlias(ty), _) if is_type(&ty.ty) => Ordering::Less,
626 (_, TyAlias(ty)) if is_type(&ty.ty) => Ordering::Greater,
627 (TyAlias(..), _) => Ordering::Less,
628 (_, TyAlias(..)) => Ordering::Greater,
629 (Const(..), _) => Ordering::Less,
630 (_, Const(..)) => Ordering::Greater,
631 (MacCall(..), _) => Ordering::Less,
632 (_, MacCall(..)) => Ordering::Greater,
634 let mut prev_kind = None;
635 for (buf, item) in buffer {
636 // Make sure that there are at least a single empty line between
637 // different impl items.
640 .map_or(false, |prev_kind| need_empty_line(prev_kind, &item.kind))
644 let indent_str = self.block_indent.to_string_with_newline(self.config);
645 self.push_str(&indent_str);
646 self.push_str(buf.trim());
647 prev_kind = Some(item.kind.clone());
651 self.visit_impl_item(item);
657 pub(crate) fn format_impl(
658 context: &RewriteContext<'_>,
662 ) -> Option<String> {
669 let mut result = String::with_capacity(128);
670 let ref_and_type = format_impl_ref_and_type(context, item, iimpl, offset)?;
671 let sep = offset.to_string_with_newline(context.config);
672 result.push_str(&ref_and_type);
674 let where_budget = if result.contains('\n') {
675 context.config.max_width()
677 context.budget(last_line_width(&result))
680 let mut option = WhereClauseOption::snuggled(&ref_and_type);
681 let snippet = context.snippet(item.span);
682 let open_pos = snippet.find_uncommented("{")? + 1;
683 if !contains_comment(&snippet[open_pos..])
685 && generics.where_clause.predicates.len() == 1
686 && !result.contains('\n')
688 option.suppress_comma();
690 option.allow_single_line();
693 let missing_span = mk_sp(self_ty.span.hi(), item.span.hi());
694 let where_span_end = context.snippet_provider.opt_span_before(missing_span, "{");
695 let where_clause_str = rewrite_where_clause(
697 &generics.where_clause.predicates,
698 generics.where_clause.span,
699 context.config.brace_style(),
700 Shape::legacy(where_budget, offset.block_only()),
708 // If there is no where-clause, we may have missing comments between the trait name and
709 // the opening brace.
710 if generics.where_clause.predicates.is_empty() {
711 if let Some(hi) = where_span_end {
712 match recover_missing_comment_in_span(
713 mk_sp(self_ty.span.hi(), hi),
714 Shape::indented(offset, context.config),
716 last_line_width(&result),
718 Some(ref missing_comment) if !missing_comment.is_empty() => {
719 result.push_str(missing_comment);
726 if is_impl_single_line(context, items.as_slice(), &result, &where_clause_str, item)? {
727 result.push_str(&where_clause_str);
728 if where_clause_str.contains('\n') || last_line_contains_single_line_comment(&result) {
729 // if the where_clause contains extra comments AND
730 // there is only one where-clause predicate
731 // recover the suppressed comma in single line where_clause formatting
732 if generics.where_clause.predicates.len() == 1 {
735 result.push_str(&format!("{}{{{}}}", sep, sep));
737 result.push_str(" {}");
742 result.push_str(&where_clause_str);
744 let need_newline = last_line_contains_single_line_comment(&result) || result.contains('\n');
745 match context.config.brace_style() {
746 _ if need_newline => result.push_str(&sep),
747 BraceStyle::AlwaysNextLine => result.push_str(&sep),
748 BraceStyle::PreferSameLine => result.push(' '),
749 BraceStyle::SameLineWhere => {
750 if !where_clause_str.is_empty() {
751 result.push_str(&sep);
759 // this is an impl body snippet(impl SampleImpl { /* here */ })
760 let lo = max(self_ty.span.hi(), generics.where_clause.span.hi());
761 let snippet = context.snippet(mk_sp(lo, item.span.hi()));
762 let open_pos = snippet.find_uncommented("{")? + 1;
764 if !items.is_empty() || contains_comment(&snippet[open_pos..]) {
765 let mut visitor = FmtVisitor::from_context(context);
766 let item_indent = offset.block_only().block_indent(context.config);
767 visitor.block_indent = item_indent;
768 visitor.last_pos = lo + BytePos(open_pos as u32);
770 visitor.visit_attrs(&item.attrs, ast::AttrStyle::Inner);
771 visitor.visit_impl_items(items);
773 visitor.format_missing(item.span.hi() - BytePos(1));
775 let inner_indent_str = visitor.block_indent.to_string_with_newline(context.config);
776 let outer_indent_str = offset.block_only().to_string_with_newline(context.config);
778 result.push_str(&inner_indent_str);
779 result.push_str(visitor.buffer.trim());
780 result.push_str(&outer_indent_str);
781 } else if need_newline || !context.config.empty_item_single_line() {
782 result.push_str(&sep);
790 fn is_impl_single_line(
791 context: &RewriteContext<'_>,
792 items: &[ptr::P<ast::AssocItem>],
794 where_clause_str: &str,
797 let snippet = context.snippet(item.span);
798 let open_pos = snippet.find_uncommented("{")? + 1;
801 context.config.empty_item_single_line()
803 && !result.contains('\n')
804 && result.len() + where_clause_str.len() <= context.config.max_width()
805 && !contains_comment(&snippet[open_pos..]),
809 fn format_impl_ref_and_type(
810 context: &RewriteContext<'_>,
814 ) -> Option<String> {
821 of_trait: ref trait_ref,
825 let mut result = String::with_capacity(128);
827 result.push_str(&format_visibility(context, &item.vis));
828 result.push_str(format_defaultness(defaultness));
829 result.push_str(format_unsafety(unsafety));
831 let shape = if context.config.version() == Version::Two {
832 Shape::indented(offset + last_line_width(&result), context.config)
834 generics_shape_from_config(
836 Shape::indented(offset + last_line_width(&result), context.config),
840 let generics_str = rewrite_generics(context, "impl", generics, shape)?;
841 result.push_str(&generics_str);
842 result.push_str(format_constness_right(constness));
844 let polarity_str = match polarity {
845 ast::ImplPolarity::Negative(_) => "!",
846 ast::ImplPolarity::Positive => "",
849 let polarity_overhead;
850 let trait_ref_overhead;
851 if let Some(ref trait_ref) = *trait_ref {
852 let result_len = last_line_width(&result);
853 result.push_str(&rewrite_trait_ref(
860 polarity_overhead = 0; // already written
861 trait_ref_overhead = " for".len();
863 polarity_overhead = polarity_str.len();
864 trait_ref_overhead = 0;
867 // Try to put the self type in a single line.
868 let curly_brace_overhead = if generics.where_clause.predicates.is_empty() {
869 // If there is no where-clause adapt budget for type formatting to take space and curly
870 // brace into account.
871 match context.config.brace_style() {
872 BraceStyle::AlwaysNextLine => 0,
879 last_line_width(&result) + polarity_overhead + trait_ref_overhead + curly_brace_overhead;
880 // 1 = space before the type.
881 let budget = context.budget(used_space + 1);
882 if let Some(self_ty_str) = self_ty.rewrite(context, Shape::legacy(budget, offset)) {
883 if !self_ty_str.contains('\n') {
884 if trait_ref.is_some() {
885 result.push_str(" for ");
888 result.push_str(polarity_str);
890 result.push_str(&self_ty_str);
895 // Couldn't fit the self type on a single line, put it on a new line.
897 // Add indentation of one additional tab.
898 let new_line_offset = offset.block_indent(context.config);
899 result.push_str(&new_line_offset.to_string(context.config));
900 if trait_ref.is_some() {
901 result.push_str("for ");
903 result.push_str(polarity_str);
905 let budget = context.budget(last_line_width(&result) + polarity_overhead);
906 let type_offset = match context.config.indent_style() {
907 IndentStyle::Visual => new_line_offset + trait_ref_overhead,
908 IndentStyle::Block => new_line_offset,
910 result.push_str(&*self_ty.rewrite(context, Shape::legacy(budget, type_offset))?);
914 fn rewrite_trait_ref(
915 context: &RewriteContext<'_>,
916 trait_ref: &ast::TraitRef,
920 ) -> Option<String> {
921 // 1 = space between generics and trait_ref
922 let used_space = 1 + polarity_str.len() + result_len;
923 let shape = Shape::indented(offset + used_space, context.config);
924 if let Some(trait_ref_str) = trait_ref.rewrite(context, shape) {
925 if !trait_ref_str.contains('\n') {
926 return Some(format!(" {}{}", polarity_str, trait_ref_str));
929 // We could not make enough space for trait_ref, so put it on new line.
930 let offset = offset.block_indent(context.config);
931 let shape = Shape::indented(offset, context.config);
932 let trait_ref_str = trait_ref.rewrite(context, shape)?;
935 offset.to_string_with_newline(context.config),
941 pub(crate) struct StructParts<'a> {
943 ident: symbol::Ident,
944 vis: &'a ast::Visibility,
945 def: &'a ast::VariantData,
946 generics: Option<&'a ast::Generics>,
950 impl<'a> StructParts<'a> {
951 fn format_header(&self, context: &RewriteContext<'_>, offset: Indent) -> String {
952 format_header(context, self.prefix, self.ident, self.vis, offset)
955 fn from_variant(variant: &'a ast::Variant) -> Self {
958 ident: variant.ident,
959 vis: &DEFAULT_VISIBILITY,
966 pub(crate) fn from_item(item: &'a ast::Item) -> Self {
967 let (prefix, def, generics) = match item.kind {
968 ast::ItemKind::Struct(ref def, ref generics) => ("struct ", def, generics),
969 ast::ItemKind::Union(ref def, ref generics) => ("union ", def, generics),
977 generics: Some(generics),
984 context: &RewriteContext<'_>,
985 struct_parts: &StructParts<'_>,
987 one_line_width: Option<usize>,
988 ) -> Option<String> {
989 match *struct_parts.def {
990 ast::VariantData::Unit(..) => format_unit_struct(context, struct_parts, offset),
991 ast::VariantData::Tuple(ref fields, _) => {
992 format_tuple_struct(context, struct_parts, fields, offset)
994 ast::VariantData::Struct(ref fields, _) => {
995 format_struct_struct(context, struct_parts, fields, offset, one_line_width)
1000 pub(crate) fn format_trait(
1001 context: &RewriteContext<'_>,
1004 ) -> Option<String> {
1005 if let ast::ItemKind::Trait(trait_kind) = &item.kind {
1013 let mut result = String::with_capacity(128);
1014 let header = format!(
1016 format_visibility(context, &item.vis),
1017 format_unsafety(unsafety),
1018 format_auto(is_auto),
1020 result.push_str(&header);
1022 let body_lo = context.snippet_provider.span_after(item.span, "{");
1024 let shape = Shape::indented(offset, context.config).offset_left(result.len())?;
1026 rewrite_generics(context, rewrite_ident(context, item.ident), generics, shape)?;
1027 result.push_str(&generics_str);
1029 // FIXME(#2055): rustfmt fails to format when there are comments between trait bounds.
1030 if !bounds.is_empty() {
1031 let ident_hi = context
1033 .span_after(item.span, item.ident.as_str());
1034 let bound_hi = bounds.last().unwrap().span().hi();
1035 let snippet = context.snippet(mk_sp(ident_hi, bound_hi));
1036 if contains_comment(snippet) {
1040 result = rewrite_assign_rhs_with(
1045 &RhsAssignKind::Bounds,
1046 RhsTactics::ForceNextLineWithoutIndent,
1050 // Rewrite where-clause.
1051 if !generics.where_clause.predicates.is_empty() {
1052 let where_on_new_line = context.config.indent_style() != IndentStyle::Block;
1054 let where_budget = context.budget(last_line_width(&result));
1055 let pos_before_where = if bounds.is_empty() {
1056 generics.where_clause.span.lo()
1058 bounds[bounds.len() - 1].span().hi()
1060 let option = WhereClauseOption::snuggled(&generics_str);
1061 let where_clause_str = rewrite_where_clause(
1063 &generics.where_clause.predicates,
1064 generics.where_clause.span,
1065 context.config.brace_style(),
1066 Shape::legacy(where_budget, offset.block_only()),
1073 // If the where-clause cannot fit on the same line,
1074 // put the where-clause on a new line
1075 if !where_clause_str.contains('\n')
1076 && last_line_width(&result) + where_clause_str.len() + offset.width()
1077 > context.config.comment_width()
1079 let width = offset.block_indent + context.config.tab_spaces() - 1;
1080 let where_indent = Indent::new(0, width);
1081 result.push_str(&where_indent.to_string_with_newline(context.config));
1083 result.push_str(&where_clause_str);
1085 let item_snippet = context.snippet(item.span);
1086 if let Some(lo) = item_snippet.find('/') {
1088 let comment_hi = body_lo - BytePos(1);
1089 let comment_lo = item.span.lo() + BytePos(lo as u32);
1090 if comment_lo < comment_hi {
1091 match recover_missing_comment_in_span(
1092 mk_sp(comment_lo, comment_hi),
1093 Shape::indented(offset, context.config),
1095 last_line_width(&result),
1097 Some(ref missing_comment) if !missing_comment.is_empty() => {
1098 result.push_str(missing_comment);
1106 let block_span = mk_sp(generics.where_clause.span.hi(), item.span.hi());
1107 let snippet = context.snippet(block_span);
1108 let open_pos = snippet.find_uncommented("{")? + 1;
1110 match context.config.brace_style() {
1111 _ if last_line_contains_single_line_comment(&result)
1112 || last_line_width(&result) + 2 > context.budget(offset.width()) =>
1114 result.push_str(&offset.to_string_with_newline(context.config));
1116 _ if context.config.empty_item_single_line()
1118 && !result.contains('\n')
1119 && !contains_comment(&snippet[open_pos..]) =>
1121 result.push_str(" {}");
1122 return Some(result);
1124 BraceStyle::AlwaysNextLine => {
1125 result.push_str(&offset.to_string_with_newline(context.config));
1127 BraceStyle::PreferSameLine => result.push(' '),
1128 BraceStyle::SameLineWhere => {
1129 if result.contains('\n')
1130 || (!generics.where_clause.predicates.is_empty() && !items.is_empty())
1132 result.push_str(&offset.to_string_with_newline(context.config));
1140 let outer_indent_str = offset.block_only().to_string_with_newline(context.config);
1142 if !items.is_empty() || contains_comment(&snippet[open_pos..]) {
1143 let mut visitor = FmtVisitor::from_context(context);
1144 visitor.block_indent = offset.block_only().block_indent(context.config);
1145 visitor.last_pos = block_span.lo() + BytePos(open_pos as u32);
1148 visitor.visit_trait_item(item);
1151 visitor.format_missing(item.span.hi() - BytePos(1));
1153 let inner_indent_str = visitor.block_indent.to_string_with_newline(context.config);
1155 result.push_str(&inner_indent_str);
1156 result.push_str(visitor.buffer.trim());
1157 result.push_str(&outer_indent_str);
1158 } else if result.contains('\n') {
1159 result.push_str(&outer_indent_str);
1169 pub(crate) struct TraitAliasBounds<'a> {
1170 generic_bounds: &'a ast::GenericBounds,
1171 generics: &'a ast::Generics,
1174 impl<'a> Rewrite for TraitAliasBounds<'a> {
1175 fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
1176 let generic_bounds_str = self.generic_bounds.rewrite(context, shape)?;
1178 let mut option = WhereClauseOption::new(true, WhereClauseSpace::None);
1179 option.allow_single_line();
1181 let where_str = rewrite_where_clause(
1183 &self.generics.where_clause.predicates,
1184 self.generics.where_clause.span,
1185 context.config.brace_style(),
1190 self.generics.where_clause.span.lo(),
1194 let fits_single_line = !generic_bounds_str.contains('\n')
1195 && !where_str.contains('\n')
1196 && generic_bounds_str.len() + where_str.len() < shape.width;
1197 let space = if generic_bounds_str.is_empty() || where_str.is_empty() {
1199 } else if fits_single_line {
1202 shape.indent.to_string_with_newline(context.config)
1205 Some(format!("{}{}{}", generic_bounds_str, space, where_str))
1209 pub(crate) fn format_trait_alias(
1210 context: &RewriteContext<'_>,
1211 ident: symbol::Ident,
1212 vis: &ast::Visibility,
1213 generics: &ast::Generics,
1214 generic_bounds: &ast::GenericBounds,
1216 ) -> Option<String> {
1217 let alias = rewrite_ident(context, ident);
1218 // 6 = "trait ", 2 = " ="
1219 let g_shape = shape.offset_left(6)?.sub_width(2)?;
1220 let generics_str = rewrite_generics(context, alias, generics, g_shape)?;
1221 let vis_str = format_visibility(context, vis);
1222 let lhs = format!("{}trait {} =", vis_str, generics_str);
1224 let trait_alias_bounds = TraitAliasBounds {
1231 &trait_alias_bounds,
1232 &RhsAssignKind::Bounds,
1233 shape.sub_width(1)?,
1238 fn format_unit_struct(
1239 context: &RewriteContext<'_>,
1240 p: &StructParts<'_>,
1242 ) -> Option<String> {
1243 let header_str = format_header(context, p.prefix, p.ident, p.vis, offset);
1244 let generics_str = if let Some(generics) = p.generics {
1245 let hi = context.snippet_provider.span_before(p.span, ";");
1249 context.config.brace_style(),
1252 // make a span that starts right after `struct Foo`
1253 mk_sp(p.ident.span.hi(), hi),
1254 last_line_width(&header_str),
1259 Some(format!("{}{};", header_str, generics_str))
1262 pub(crate) fn format_struct_struct(
1263 context: &RewriteContext<'_>,
1264 struct_parts: &StructParts<'_>,
1265 fields: &[ast::FieldDef],
1267 one_line_width: Option<usize>,
1268 ) -> Option<String> {
1269 let mut result = String::with_capacity(1024);
1270 let span = struct_parts.span;
1272 let header_str = struct_parts.format_header(context, offset);
1273 result.push_str(&header_str);
1275 let header_hi = struct_parts.ident.span.hi();
1276 let body_lo = context.snippet_provider.span_after(span, "{");
1278 let generics_str = match struct_parts.generics {
1279 Some(g) => format_generics(
1282 context.config.brace_style(),
1283 if fields.is_empty() {
1284 BracePos::ForceSameLine
1289 // make a span that starts right after `struct Foo`
1290 mk_sp(header_hi, body_lo),
1291 last_line_width(&result),
1294 // 3 = ` {}`, 2 = ` {`.
1295 let overhead = if fields.is_empty() { 3 } else { 2 };
1296 if (context.config.brace_style() == BraceStyle::AlwaysNextLine && !fields.is_empty())
1297 || context.config.max_width() < overhead + result.len()
1299 format!("\n{}{{", offset.block_only().to_string(context.config))
1306 let overhead = if fields.is_empty() { 1 } else { 0 };
1307 let total_width = result.len() + generics_str.len() + overhead;
1308 if !generics_str.is_empty()
1309 && !generics_str.contains('\n')
1310 && total_width > context.config.max_width()
1313 result.push_str(&offset.to_string(context.config));
1314 result.push_str(generics_str.trim_start());
1316 result.push_str(&generics_str);
1319 if fields.is_empty() {
1320 let inner_span = mk_sp(body_lo, span.hi() - BytePos(1));
1321 format_empty_struct_or_tuple(context, inner_span, offset, &mut result, "", "}");
1322 return Some(result);
1326 let one_line_budget = context.budget(result.len() + 3 + offset.width());
1327 let one_line_budget =
1328 one_line_width.map_or(0, |one_line_width| min(one_line_width, one_line_budget));
1330 let items_str = rewrite_with_alignment(
1333 Shape::indented(offset.block_indent(context.config), context.config).sub_width(1)?,
1334 mk_sp(body_lo, span.hi()),
1338 if !items_str.contains('\n')
1339 && !result.contains('\n')
1340 && items_str.len() <= one_line_budget
1341 && !last_line_contains_single_line_comment(&items_str)
1343 Some(format!("{} {} }}", result, items_str))
1349 .block_indent(context.config)
1350 .to_string(context.config),
1352 offset.to_string(context.config)
1357 fn get_bytepos_after_visibility(vis: &ast::Visibility, default_span: Span) -> BytePos {
1359 ast::VisibilityKind::Crate(..) | ast::VisibilityKind::Restricted { .. } => vis.span.hi(),
1360 _ => default_span.lo(),
1364 // Format tuple or struct without any fields. We need to make sure that the comments
1365 // inside the delimiters are preserved.
1366 fn format_empty_struct_or_tuple(
1367 context: &RewriteContext<'_>,
1370 result: &mut String,
1374 // 3 = " {}" or "();"
1375 let used_width = last_line_used_width(result, offset.width()) + 3;
1376 if used_width > context.config.max_width() {
1377 result.push_str(&offset.to_string_with_newline(context.config))
1379 result.push_str(opener);
1380 match rewrite_missing_comment(span, Shape::indented(offset, context.config), context) {
1381 Some(ref s) if s.is_empty() => (),
1383 if !is_single_line(s) || first_line_contains_single_line_comment(s) {
1384 let nested_indent_str = offset
1385 .block_indent(context.config)
1386 .to_string_with_newline(context.config);
1387 result.push_str(&nested_indent_str);
1390 if last_line_contains_single_line_comment(s) {
1391 result.push_str(&offset.to_string_with_newline(context.config));
1394 None => result.push_str(context.snippet(span)),
1396 result.push_str(closer);
1399 fn format_tuple_struct(
1400 context: &RewriteContext<'_>,
1401 struct_parts: &StructParts<'_>,
1402 fields: &[ast::FieldDef],
1404 ) -> Option<String> {
1405 let mut result = String::with_capacity(1024);
1406 let span = struct_parts.span;
1408 let header_str = struct_parts.format_header(context, offset);
1409 result.push_str(&header_str);
1411 let body_lo = if fields.is_empty() {
1412 let lo = get_bytepos_after_visibility(struct_parts.vis, span);
1415 .span_after(mk_sp(lo, span.hi()), "(")
1419 let body_hi = if fields.is_empty() {
1422 .span_after(mk_sp(body_lo, span.hi()), ")")
1424 // This is a dirty hack to work around a missing `)` from the span of the last field.
1425 let last_arg_span = fields[fields.len() - 1].span;
1428 .opt_span_after(mk_sp(last_arg_span.hi(), span.hi()), ")")
1429 .unwrap_or_else(|| last_arg_span.hi())
1432 let where_clause_str = match struct_parts.generics {
1434 let budget = context.budget(last_line_width(&header_str));
1435 let shape = Shape::legacy(budget, offset);
1436 let generics_str = rewrite_generics(context, "", generics, shape)?;
1437 result.push_str(&generics_str);
1439 let where_budget = context.budget(last_line_width(&result));
1440 let option = WhereClauseOption::new(true, WhereClauseSpace::Newline);
1441 rewrite_where_clause(
1443 &generics.where_clause.predicates,
1444 generics.where_clause.span,
1445 context.config.brace_style(),
1446 Shape::legacy(where_budget, offset.block_only()),
1454 None => "".to_owned(),
1457 if fields.is_empty() {
1458 let body_hi = context
1460 .span_before(mk_sp(body_lo, span.hi()), ")");
1461 let inner_span = mk_sp(body_lo, body_hi);
1462 format_empty_struct_or_tuple(context, inner_span, offset, &mut result, "(", ")");
1464 let shape = Shape::indented(offset, context.config).sub_width(1)?;
1465 let lo = if let Some(generics) = struct_parts.generics {
1468 struct_parts.ident.span.hi()
1470 result = overflow::rewrite_with_parens(
1475 mk_sp(lo, span.hi()),
1476 context.config.fn_call_width(),
1481 if !where_clause_str.is_empty()
1482 && !where_clause_str.contains('\n')
1483 && (result.contains('\n')
1484 || offset.block_indent + result.len() + where_clause_str.len() + 1
1485 > context.config.max_width())
1487 // We need to put the where-clause on a new line, but we didn't
1488 // know that earlier, so the where-clause will not be indented properly.
1491 &(offset.block_only() + (context.config.tab_spaces() - 1)).to_string(context.config),
1494 result.push_str(&where_clause_str);
1499 pub(crate) enum ItemVisitorKind<'a> {
1500 Item(&'a ast::Item),
1501 AssocTraitItem(&'a ast::AssocItem),
1502 AssocImplItem(&'a ast::AssocItem),
1503 ForeignItem(&'a ast::ForeignItem),
1506 struct TyAliasRewriteInfo<'c, 'g>(
1507 &'c RewriteContext<'c>,
1510 (ast::TyAliasWhereClause, ast::TyAliasWhereClause),
1516 pub(crate) fn rewrite_type_alias<'a, 'b>(
1517 ty_alias_kind: &ast::TyAlias,
1518 context: &RewriteContext<'a>,
1520 visitor_kind: &ItemVisitorKind<'b>,
1522 ) -> Option<String> {
1523 use ItemVisitorKind::*;
1531 where_predicates_split,
1533 let ty_opt = ty.as_ref();
1534 let (ident, vis) = match visitor_kind {
1535 Item(i) => (i.ident, &i.vis),
1536 AssocTraitItem(i) | AssocImplItem(i) => (i.ident, &i.vis),
1537 ForeignItem(i) => (i.ident, &i.vis),
1539 let rw_info = &TyAliasRewriteInfo(
1544 where_predicates_split,
1548 let op_ty = opaque_ty(ty);
1549 // Type Aliases are formatted slightly differently depending on the context
1550 // in which they appear, whether they are opaque, and whether they are associated.
1551 // https://rustc-dev-guide.rust-lang.org/opaque-types-type-alias-impl-trait.html
1552 // https://github.com/rust-dev-tools/fmt-rfcs/blob/master/guide/items.md#type-aliases
1553 match (visitor_kind, &op_ty) {
1554 (Item(_) | AssocTraitItem(_) | ForeignItem(_), Some(op_bounds)) => {
1555 let op = OpaqueType { bounds: op_bounds };
1556 rewrite_ty(rw_info, Some(bounds), Some(&op), vis)
1558 (Item(_) | AssocTraitItem(_) | ForeignItem(_), None) => {
1559 rewrite_ty(rw_info, Some(bounds), ty_opt, vis)
1561 (AssocImplItem(_), _) => {
1562 let result = if let Some(op_bounds) = op_ty {
1563 let op = OpaqueType { bounds: op_bounds };
1564 rewrite_ty(rw_info, Some(bounds), Some(&op), &DEFAULT_VISIBILITY)
1566 rewrite_ty(rw_info, Some(bounds), ty_opt, vis)
1569 ast::Defaultness::Default(..) => Some(format!("default {}", result)),
1576 fn rewrite_ty<R: Rewrite>(
1577 rw_info: &TyAliasRewriteInfo<'_, '_>,
1578 generic_bounds_opt: Option<&ast::GenericBounds>,
1580 vis: &ast::Visibility,
1581 ) -> Option<String> {
1582 let mut result = String::with_capacity(128);
1583 let TyAliasRewriteInfo(
1588 where_predicates_split,
1592 let (before_where_predicates, after_where_predicates) = generics
1595 .split_at(where_predicates_split);
1596 if !after_where_predicates.is_empty() {
1599 result.push_str(&format!("{}type ", format_visibility(context, vis)));
1600 let ident_str = rewrite_ident(context, ident);
1602 if generics.params.is_empty() {
1603 result.push_str(ident_str)
1606 let g_shape = Shape::indented(indent, context.config)
1607 .offset_left(result.len())?
1609 let generics_str = rewrite_generics(context, ident_str, generics, g_shape)?;
1610 result.push_str(&generics_str);
1613 if let Some(bounds) = generic_bounds_opt {
1614 if !bounds.is_empty() {
1616 let shape = Shape::indented(indent, context.config).offset_left(result.len() + 2)?;
1617 let type_bounds = bounds.rewrite(context, shape).map(|s| format!(": {}", s))?;
1618 result.push_str(&type_bounds);
1622 let where_budget = context.budget(last_line_width(&result));
1623 let mut option = WhereClauseOption::snuggled(&result);
1625 option.suppress_comma();
1627 let where_clause_str = rewrite_where_clause(
1629 before_where_predicates,
1631 context.config.brace_style(),
1632 Shape::legacy(where_budget, indent),
1639 result.push_str(&where_clause_str);
1641 if let Some(ty) = rhs {
1642 // If there's a where clause, add a newline before the assignment. Otherwise just add a
1644 let has_where = !before_where_predicates.is_empty();
1646 result.push_str(&indent.to_string_with_newline(context.config));
1651 let comment_span = context
1653 .opt_span_before(span, "=")
1654 .map(|op_lo| mk_sp(where_clauses.0.1.hi(), op_lo));
1656 let lhs = match comment_span {
1658 if contains_comment(context.snippet_provider.span_to_snippet(comment_span)?) =>
1660 let comment_shape = if has_where {
1661 Shape::indented(indent, context.config)
1663 Shape::indented(indent, context.config)
1664 .block_left(context.config.tab_spaces())?
1667 combine_strs_with_missing_comments(
1676 _ => format!("{}=", result),
1680 let shape = Shape::indented(indent, context.config).sub_width(1)?;
1681 rewrite_assign_rhs(context, lhs, &*ty, &RhsAssignKind::Ty, shape).map(|s| s + ";")
1683 Some(format!("{};", result))
1687 fn type_annotation_spacing(config: &Config) -> (&str, &str) {
1689 if config.space_before_colon() { " " } else { "" },
1690 if config.space_after_colon() { " " } else { "" },
1694 pub(crate) fn rewrite_struct_field_prefix(
1695 context: &RewriteContext<'_>,
1696 field: &ast::FieldDef,
1697 ) -> Option<String> {
1698 let vis = format_visibility(context, &field.vis);
1699 let type_annotation_spacing = type_annotation_spacing(context.config);
1700 Some(match field.ident {
1701 Some(name) => format!(
1704 rewrite_ident(context, name),
1705 type_annotation_spacing.0
1707 None => vis.to_string(),
1711 impl Rewrite for ast::FieldDef {
1712 fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
1713 rewrite_struct_field(context, self, shape, 0)
1717 pub(crate) fn rewrite_struct_field(
1718 context: &RewriteContext<'_>,
1719 field: &ast::FieldDef,
1721 lhs_max_width: usize,
1722 ) -> Option<String> {
1723 if contains_skip(&field.attrs) {
1724 return Some(context.snippet(field.span()).to_owned());
1727 let type_annotation_spacing = type_annotation_spacing(context.config);
1728 let prefix = rewrite_struct_field_prefix(context, field)?;
1730 let attrs_str = field.attrs.rewrite(context, shape)?;
1731 let attrs_extendable = field.ident.is_none() && is_attributes_extendable(&attrs_str);
1732 let missing_span = if field.attrs.is_empty() {
1733 mk_sp(field.span.lo(), field.span.lo())
1735 mk_sp(field.attrs.last().unwrap().span.hi(), field.span.lo())
1737 let mut spacing = String::from(if field.ident.is_some() {
1738 type_annotation_spacing.1
1742 // Try to put everything on a single line.
1743 let attr_prefix = combine_strs_with_missing_comments(
1751 let overhead = trimmed_last_line_width(&attr_prefix);
1752 let lhs_offset = lhs_max_width.saturating_sub(overhead);
1753 for _ in 0..lhs_offset {
1756 // In this extreme case we will be missing a space between an attribute and a field.
1757 if prefix.is_empty() && !attrs_str.is_empty() && attrs_extendable && spacing.is_empty() {
1761 .offset_left(overhead + spacing.len())
1762 .and_then(|ty_shape| field.ty.rewrite(context, ty_shape));
1763 if let Some(ref ty) = orig_ty {
1764 if !ty.contains('\n') {
1765 return Some(attr_prefix + &spacing + ty);
1769 let is_prefix_empty = prefix.is_empty();
1770 // We must use multiline. We are going to put attributes and a field on different lines.
1771 let field_str = rewrite_assign_rhs(context, prefix, &*field.ty, &RhsAssignKind::Ty, shape)?;
1772 // Remove a leading white-space from `rewrite_assign_rhs()` when rewriting a tuple struct.
1773 let field_str = if is_prefix_empty {
1774 field_str.trim_start()
1778 combine_strs_with_missing_comments(context, &attrs_str, field_str, missing_span, shape, false)
1781 pub(crate) struct StaticParts<'a> {
1783 vis: &'a ast::Visibility,
1784 ident: symbol::Ident,
1786 mutability: ast::Mutability,
1787 expr_opt: Option<&'a ptr::P<ast::Expr>>,
1788 defaultness: Option<ast::Defaultness>,
1792 impl<'a> StaticParts<'a> {
1793 pub(crate) fn from_item(item: &'a ast::Item) -> Self {
1794 let (defaultness, prefix, ty, mutability, expr) = match item.kind {
1795 ast::ItemKind::Static(ref ty, mutability, ref expr) => {
1796 (None, "static", ty, mutability, expr)
1798 ast::ItemKind::Const(defaultness, ref ty, ref expr) => {
1799 (Some(defaultness), "const", ty, ast::Mutability::Not, expr)
1801 _ => unreachable!(),
1809 expr_opt: expr.as_ref(),
1815 pub(crate) fn from_trait_item(ti: &'a ast::AssocItem) -> Self {
1816 let (defaultness, ty, expr_opt) = match ti.kind {
1817 ast::AssocItemKind::Const(defaultness, ref ty, ref expr_opt) => {
1818 (defaultness, ty, expr_opt)
1820 _ => unreachable!(),
1827 mutability: ast::Mutability::Not,
1828 expr_opt: expr_opt.as_ref(),
1829 defaultness: Some(defaultness),
1834 pub(crate) fn from_impl_item(ii: &'a ast::AssocItem) -> Self {
1835 let (defaultness, ty, expr) = match ii.kind {
1836 ast::AssocItemKind::Const(defaultness, ref ty, ref expr) => (defaultness, ty, expr),
1837 _ => unreachable!(),
1844 mutability: ast::Mutability::Not,
1845 expr_opt: expr.as_ref(),
1846 defaultness: Some(defaultness),
1853 context: &RewriteContext<'_>,
1854 static_parts: &StaticParts<'_>,
1856 ) -> Option<String> {
1857 let colon = colon_spaces(context.config);
1858 let mut prefix = format!(
1860 format_visibility(context, static_parts.vis),
1861 static_parts.defaultness.map_or("", format_defaultness),
1862 static_parts.prefix,
1863 format_mutability(static_parts.mutability),
1864 rewrite_ident(context, static_parts.ident),
1869 Shape::indented(offset.block_only(), context.config).offset_left(prefix.len() + 2)?;
1870 let ty_str = match static_parts.ty.rewrite(context, ty_shape) {
1871 Some(ty_str) => ty_str,
1873 if prefix.ends_with(' ') {
1876 let nested_indent = offset.block_indent(context.config);
1877 let nested_shape = Shape::indented(nested_indent, context.config);
1878 let ty_str = static_parts.ty.rewrite(context, nested_shape)?;
1881 nested_indent.to_string_with_newline(context.config),
1887 if let Some(expr) = static_parts.expr_opt {
1888 let comments_lo = context.snippet_provider.span_after(static_parts.span, "=");
1889 let expr_lo = expr.span.lo();
1890 let comments_span = mk_sp(comments_lo, expr_lo);
1892 let lhs = format!("{}{} =", prefix, ty_str);
1895 let remaining_width = context.budget(offset.block_indent + 1);
1896 rewrite_assign_rhs_with_comments(
1900 Shape::legacy(remaining_width, offset.block_only()),
1901 &RhsAssignKind::Expr(&expr.kind, expr.span),
1902 RhsTactics::Default,
1906 .and_then(|res| recover_comment_removed(res, static_parts.span, context))
1907 .map(|s| if s.ends_with(';') { s } else { s + ";" })
1909 Some(format!("{}{};", prefix, ty_str))
1913 // FIXME(calebcartwright) - This is a hack around a bug in the handling of TyKind::ImplTrait.
1914 // This should be removed once that bug is resolved, with the type alias formatting using the
1915 // defined Ty for the RHS directly.
1916 // https://github.com/rust-lang/rustfmt/issues/4373
1917 // https://github.com/rust-lang/rustfmt/issues/5027
1918 struct OpaqueType<'a> {
1919 bounds: &'a ast::GenericBounds,
1922 impl<'a> Rewrite for OpaqueType<'a> {
1923 fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
1924 let shape = shape.offset_left(5)?; // `impl `
1926 .rewrite(context, shape)
1927 .map(|s| format!("impl {}", s))
1931 impl Rewrite for ast::FnRetTy {
1932 fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
1934 ast::FnRetTy::Default(_) => Some(String::new()),
1935 ast::FnRetTy::Ty(ref ty) => {
1936 if context.config.version() == Version::One
1937 || context.config.indent_style() == IndentStyle::Visual
1939 let inner_width = shape.width.checked_sub(3)?;
1941 .rewrite(context, Shape::legacy(inner_width, shape.indent + 3))
1942 .map(|r| format!("-> {}", r));
1945 ty.rewrite(context, shape.offset_left(3)?)
1946 .map(|s| format!("-> {}", s))
1952 fn is_empty_infer(ty: &ast::Ty, pat_span: Span) -> bool {
1954 ast::TyKind::Infer => ty.span.hi() == pat_span.hi(),
1959 /// Recover any missing comments between the param and the type.
1963 /// A 2-len tuple with the comment before the colon in first position, and the comment after the
1964 /// colon in second position.
1965 fn get_missing_param_comments(
1966 context: &RewriteContext<'_>,
1970 ) -> (String, String) {
1971 let missing_comment_span = mk_sp(pat_span.hi(), ty_span.lo());
1973 let span_before_colon = {
1974 let missing_comment_span_hi = context
1976 .span_before(missing_comment_span, ":");
1977 mk_sp(pat_span.hi(), missing_comment_span_hi)
1979 let span_after_colon = {
1980 let missing_comment_span_lo = context
1982 .span_after(missing_comment_span, ":");
1983 mk_sp(missing_comment_span_lo, ty_span.lo())
1986 let comment_before_colon = rewrite_missing_comment(span_before_colon, shape, context)
1987 .filter(|comment| !comment.is_empty())
1988 .map_or(String::new(), |comment| format!(" {}", comment));
1989 let comment_after_colon = rewrite_missing_comment(span_after_colon, shape, context)
1990 .filter(|comment| !comment.is_empty())
1991 .map_or(String::new(), |comment| format!("{} ", comment));
1992 (comment_before_colon, comment_after_colon)
1995 impl Rewrite for ast::Param {
1996 fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
1997 let param_attrs_result = self
1999 .rewrite(context, Shape::legacy(shape.width, shape.indent))?;
2000 // N.B. Doc comments aren't typically valid syntax, but could appear
2001 // in the presence of certain macros - https://github.com/rust-lang/rustfmt/issues/4936
2002 let (span, has_multiple_attr_lines, has_doc_comments) = if !self.attrs.is_empty() {
2003 let num_attrs = self.attrs.len();
2005 mk_sp(self.attrs[num_attrs - 1].span.hi(), self.pat.span.lo()),
2006 param_attrs_result.contains('\n'),
2007 self.attrs.iter().any(|a| a.is_doc_comment()),
2010 (mk_sp(self.span.lo(), self.span.lo()), false, false)
2013 if let Some(ref explicit_self) = self.to_self() {
2014 rewrite_explicit_self(
2017 ¶m_attrs_result,
2020 has_multiple_attr_lines,
2022 } else if is_named_param(self) {
2023 let param_name = &self
2025 .rewrite(context, Shape::legacy(shape.width, shape.indent))?;
2026 let mut result = combine_strs_with_missing_comments(
2028 ¶m_attrs_result,
2032 !has_multiple_attr_lines && !has_doc_comments,
2035 if !is_empty_infer(&*self.ty, self.pat.span) {
2036 let (before_comment, after_comment) =
2037 get_missing_param_comments(context, self.pat.span, self.ty.span, shape);
2038 result.push_str(&before_comment);
2039 result.push_str(colon_spaces(context.config));
2040 result.push_str(&after_comment);
2041 let overhead = last_line_width(&result);
2042 let max_width = shape.width.checked_sub(overhead)?;
2043 if let Some(ty_str) = self
2045 .rewrite(context, Shape::legacy(max_width, shape.indent))
2047 result.push_str(&ty_str);
2049 result = combine_strs_with_missing_comments(
2051 &(param_attrs_result + &shape.to_string_with_newline(context.config)),
2055 !has_multiple_attr_lines,
2057 result.push_str(&before_comment);
2058 result.push_str(colon_spaces(context.config));
2059 result.push_str(&after_comment);
2060 let overhead = last_line_width(&result);
2061 let max_width = shape.width.checked_sub(overhead)?;
2064 .rewrite(context, Shape::legacy(max_width, shape.indent))?;
2065 result.push_str(&ty_str);
2071 self.ty.rewrite(context, shape)
2076 fn rewrite_explicit_self(
2077 context: &RewriteContext<'_>,
2078 explicit_self: &ast::ExplicitSelf,
2082 has_multiple_attr_lines: bool,
2083 ) -> Option<String> {
2084 match explicit_self.node {
2085 ast::SelfKind::Region(lt, m) => {
2086 let mut_str = format_mutability(m);
2089 let lifetime_str = l.rewrite(
2091 Shape::legacy(context.config.max_width(), Indent::empty()),
2093 Some(combine_strs_with_missing_comments(
2096 &format!("&{} {}self", lifetime_str, mut_str),
2099 !has_multiple_attr_lines,
2102 None => Some(combine_strs_with_missing_comments(
2105 &format!("&{}self", mut_str),
2108 !has_multiple_attr_lines,
2112 ast::SelfKind::Explicit(ref ty, mutability) => {
2113 let type_str = ty.rewrite(
2115 Shape::legacy(context.config.max_width(), Indent::empty()),
2118 Some(combine_strs_with_missing_comments(
2121 &format!("{}self: {}", format_mutability(mutability), type_str),
2124 !has_multiple_attr_lines,
2127 ast::SelfKind::Value(mutability) => Some(combine_strs_with_missing_comments(
2130 &format!("{}self", format_mutability(mutability)),
2133 !has_multiple_attr_lines,
2138 pub(crate) fn span_lo_for_param(param: &ast::Param) -> BytePos {
2139 if param.attrs.is_empty() {
2140 if is_named_param(param) {
2146 param.attrs[0].span.lo()
2150 pub(crate) fn span_hi_for_param(context: &RewriteContext<'_>, param: &ast::Param) -> BytePos {
2151 match param.ty.kind {
2152 ast::TyKind::Infer if context.snippet(param.ty.span) == "_" => param.ty.span.hi(),
2153 ast::TyKind::Infer if is_named_param(param) => param.pat.span.hi(),
2154 _ => param.ty.span.hi(),
2158 pub(crate) fn is_named_param(param: &ast::Param) -> bool {
2159 if let ast::PatKind::Ident(_, ident, _) = param.pat.kind {
2160 ident.name != symbol::kw::Empty
2166 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
2167 pub(crate) enum FnBraceStyle {
2173 // Return type is (result, force_new_line_for_brace)
2175 context: &RewriteContext<'_>,
2177 ident: symbol::Ident,
2180 fn_brace_style: FnBraceStyle,
2181 ) -> Option<(String, bool, bool)> {
2182 let mut force_new_line_for_brace = false;
2184 let where_clause = &fn_sig.generics.where_clause;
2186 let mut result = String::with_capacity(1024);
2187 result.push_str(&fn_sig.to_str(context));
2190 result.push_str("fn ");
2193 let overhead = if let FnBraceStyle::SameLine = fn_brace_style {
2200 let used_width = last_line_used_width(&result, indent.width());
2201 let one_line_budget = context.budget(used_width + overhead);
2203 width: one_line_budget,
2207 let fd = fn_sig.decl;
2208 let generics_str = rewrite_generics(
2210 rewrite_ident(context, ident),
2214 result.push_str(&generics_str);
2216 let snuggle_angle_bracket = generics_str
2219 .map_or(false, |l| l.trim_start().len() == 1);
2221 // Note that the width and indent don't really matter, we'll re-layout the
2222 // return type later anyway.
2225 .rewrite(context, Shape::indented(indent, context.config))?;
2227 let multi_line_ret_str = ret_str.contains('\n');
2228 let ret_str_len = if multi_line_ret_str { 0 } else { ret_str.len() };
2231 let (one_line_budget, multi_line_budget, mut param_indent) = compute_budgets_for_params(
2241 "rewrite_fn_base: one_line_budget: {}, multi_line_budget: {}, param_indent: {:?}",
2242 one_line_budget, multi_line_budget, param_indent
2246 // Check if vertical layout was forced.
2247 if one_line_budget == 0
2248 && !snuggle_angle_bracket
2249 && context.config.indent_style() == IndentStyle::Visual
2251 result.push_str(¶m_indent.to_string_with_newline(context.config));
2254 let params_end = if fd.inputs.is_empty() {
2257 .span_after(mk_sp(fn_sig.generics.span.hi(), span.hi()), ")")
2259 let last_span = mk_sp(fd.inputs[fd.inputs.len() - 1].span().hi(), span.hi());
2260 context.snippet_provider.span_after(last_span, ")")
2262 let params_span = mk_sp(
2265 .span_after(mk_sp(fn_sig.generics.span.hi(), span.hi()), "("),
2268 let param_str = rewrite_params(
2279 let put_params_in_block = match context.config.indent_style() {
2280 IndentStyle::Block => param_str.contains('\n') || param_str.len() > one_line_budget,
2282 } && !fd.inputs.is_empty();
2284 let mut params_last_line_contains_comment = false;
2285 let mut no_params_and_over_max_width = false;
2287 if put_params_in_block {
2288 param_indent = indent.block_indent(context.config);
2289 result.push_str(¶m_indent.to_string_with_newline(context.config));
2290 result.push_str(¶m_str);
2291 result.push_str(&indent.to_string_with_newline(context.config));
2294 result.push_str(¶m_str);
2295 let used_width = last_line_used_width(&result, indent.width()) + first_line_width(&ret_str);
2296 // Put the closing brace on the next line if it overflows the max width.
2298 let closing_paren_overflow_max_width =
2299 fd.inputs.is_empty() && used_width + 1 > context.config.max_width();
2300 // If the last line of params contains comment, we cannot put the closing paren
2301 // on the same line.
2302 params_last_line_contains_comment = param_str
2305 .map_or(false, |last_line| last_line.contains("//"));
2307 if context.config.version() == Version::Two {
2308 if closing_paren_overflow_max_width {
2310 result.push_str(&indent.to_string_with_newline(context.config));
2311 no_params_and_over_max_width = true;
2312 } else if params_last_line_contains_comment {
2313 result.push_str(&indent.to_string_with_newline(context.config));
2315 no_params_and_over_max_width = true;
2320 if closing_paren_overflow_max_width || params_last_line_contains_comment {
2321 result.push_str(&indent.to_string_with_newline(context.config));
2328 if let ast::FnRetTy::Ty(..) = fd.output {
2329 let ret_should_indent = match context.config.indent_style() {
2330 // If our params are block layout then we surely must have space.
2331 IndentStyle::Block if put_params_in_block || fd.inputs.is_empty() => false,
2332 _ if params_last_line_contains_comment => false,
2333 _ if result.contains('\n') || multi_line_ret_str => true,
2335 // If the return type would push over the max width, then put the return type on
2336 // a new line. With the +1 for the signature length an additional space between
2337 // the closing parenthesis of the param and the arrow '->' is considered.
2338 let mut sig_length = result.len() + indent.width() + ret_str_len + 1;
2340 // If there is no where-clause, take into account the space after the return type
2342 if where_clause.predicates.is_empty() {
2346 sig_length > context.config.max_width()
2349 let ret_shape = if ret_should_indent {
2350 if context.config.version() == Version::One
2351 || context.config.indent_style() == IndentStyle::Visual
2353 let indent = if param_str.is_empty() {
2354 // Aligning with non-existent params looks silly.
2355 force_new_line_for_brace = true;
2358 // FIXME: we might want to check that using the param indent
2359 // doesn't blow our budget, and if it does, then fallback to
2360 // the where-clause indent.
2364 result.push_str(&indent.to_string_with_newline(context.config));
2365 Shape::indented(indent, context.config)
2367 let mut ret_shape = Shape::indented(indent, context.config);
2368 if param_str.is_empty() {
2369 // Aligning with non-existent params looks silly.
2370 force_new_line_for_brace = true;
2371 ret_shape = if context.use_block_indent() {
2372 ret_shape.offset_left(4).unwrap_or(ret_shape)
2374 ret_shape.indent = ret_shape.indent + 4;
2379 result.push_str(&ret_shape.indent.to_string_with_newline(context.config));
2383 if context.config.version() == Version::Two {
2384 if !param_str.is_empty() || !no_params_and_over_max_width {
2391 let ret_shape = Shape::indented(indent, context.config);
2393 .offset_left(last_line_width(&result))
2394 .unwrap_or(ret_shape)
2397 if multi_line_ret_str || ret_should_indent {
2398 // Now that we know the proper indent and width, we need to
2399 // re-layout the return type.
2400 let ret_str = fd.output.rewrite(context, ret_shape)?;
2401 result.push_str(&ret_str);
2403 result.push_str(&ret_str);
2406 // Comment between return type and the end of the decl.
2407 let snippet_lo = fd.output.span().hi();
2408 if where_clause.predicates.is_empty() {
2409 let snippet_hi = span.hi();
2410 let snippet = context.snippet(mk_sp(snippet_lo, snippet_hi));
2411 // Try to preserve the layout of the original snippet.
2412 let original_starts_with_newline = snippet
2414 .map_or(false, |i| starts_with_newline(&snippet[i..]));
2415 let original_ends_with_newline = snippet
2416 .rfind(|c| c != ' ')
2417 .map_or(false, |i| snippet[i..].ends_with('\n'));
2418 let snippet = snippet.trim();
2419 if !snippet.is_empty() {
2420 result.push(if original_starts_with_newline {
2425 result.push_str(snippet);
2426 if original_ends_with_newline {
2427 force_new_line_for_brace = true;
2433 let pos_before_where = match fd.output {
2434 ast::FnRetTy::Default(..) => params_span.hi(),
2435 ast::FnRetTy::Ty(ref ty) => ty.span.hi(),
2438 let is_params_multi_lined = param_str.contains('\n');
2440 let space = if put_params_in_block && ret_str.is_empty() {
2441 WhereClauseSpace::Space
2443 WhereClauseSpace::Newline
2445 let mut option = WhereClauseOption::new(fn_brace_style == FnBraceStyle::None, space);
2446 if is_params_multi_lined {
2447 option.veto_single_line();
2449 let where_clause_str = rewrite_where_clause(
2451 &where_clause.predicates,
2453 context.config.brace_style(),
2454 Shape::indented(indent, context.config),
2461 // If there are neither where-clause nor return type, we may be missing comments between
2463 if where_clause_str.is_empty() {
2464 if let ast::FnRetTy::Default(ret_span) = fd.output {
2465 match recover_missing_comment_in_span(
2466 mk_sp(params_span.hi(), ret_span.hi()),
2469 last_line_width(&result),
2471 Some(ref missing_comment) if !missing_comment.is_empty() => {
2472 result.push_str(missing_comment);
2473 force_new_line_for_brace = true;
2480 result.push_str(&where_clause_str);
2482 let ends_with_comment = last_line_contains_single_line_comment(&result);
2483 force_new_line_for_brace |= ends_with_comment;
2484 force_new_line_for_brace |=
2485 is_params_multi_lined && context.config.where_single_line() && !where_clause_str.is_empty();
2486 Some((result, ends_with_comment, force_new_line_for_brace))
2489 /// Kind of spaces to put before `where`.
2490 #[derive(Copy, Clone)]
2491 enum WhereClauseSpace {
2500 #[derive(Copy, Clone)]
2501 struct WhereClauseOption {
2502 suppress_comma: bool, // Force no trailing comma
2503 snuggle: WhereClauseSpace,
2504 allow_single_line: bool, // Try single line where-clause instead of vertical layout
2505 veto_single_line: bool, // Disallow a single-line where-clause.
2508 impl WhereClauseOption {
2509 fn new(suppress_comma: bool, snuggle: WhereClauseSpace) -> WhereClauseOption {
2513 allow_single_line: false,
2514 veto_single_line: false,
2518 fn snuggled(current: &str) -> WhereClauseOption {
2520 suppress_comma: false,
2521 snuggle: if last_line_width(current) == 1 {
2522 WhereClauseSpace::Space
2524 WhereClauseSpace::Newline
2526 allow_single_line: false,
2527 veto_single_line: false,
2531 fn suppress_comma(&mut self) {
2532 self.suppress_comma = true
2535 fn allow_single_line(&mut self) {
2536 self.allow_single_line = true
2539 fn snuggle(&mut self) {
2540 self.snuggle = WhereClauseSpace::Space
2543 fn veto_single_line(&mut self) {
2544 self.veto_single_line = true;
2549 context: &RewriteContext<'_>,
2550 params: &[ast::Param],
2551 one_line_budget: usize,
2552 multi_line_budget: usize,
2554 param_indent: Indent,
2557 ) -> Option<String> {
2558 if params.is_empty() {
2559 let comment = context
2563 span.hi() - BytePos(1),
2566 return Some(comment.to_owned());
2568 let param_items: Vec<_> = itemize_list(
2569 context.snippet_provider,
2573 |param| span_lo_for_param(param),
2574 |param| param.ty.span.hi(),
2577 .rewrite(context, Shape::legacy(multi_line_budget, param_indent))
2578 .or_else(|| Some(context.snippet(param.span()).to_owned()))
2586 let tactic = definitive_tactic(
2591 .to_list_tactic(param_items.len()),
2595 let budget = match tactic {
2596 DefinitiveListTactic::Horizontal => one_line_budget,
2597 _ => multi_line_budget,
2599 let indent = match context.config.indent_style() {
2600 IndentStyle::Block => indent.block_indent(context.config),
2601 IndentStyle::Visual => param_indent,
2603 let trailing_separator = if variadic {
2604 SeparatorTactic::Never
2606 match context.config.indent_style() {
2607 IndentStyle::Block => context.config.trailing_comma(),
2608 IndentStyle::Visual => SeparatorTactic::Never,
2611 let fmt = ListFormatting::new(Shape::legacy(budget, indent), context.config)
2613 .trailing_separator(trailing_separator)
2614 .ends_with_newline(tactic.ends_with_newline(context.config.indent_style()))
2615 .preserve_newline(true);
2616 write_list(¶m_items, &fmt)
2619 fn compute_budgets_for_params(
2620 context: &RewriteContext<'_>,
2624 fn_brace_style: FnBraceStyle,
2625 force_vertical_layout: bool,
2626 ) -> Option<(usize, usize, Indent)> {
2628 "compute_budgets_for_params {} {:?}, {}, {:?}",
2634 // Try keeping everything on the same line.
2635 if !result.contains('\n') && !force_vertical_layout {
2636 // 2 = `()`, 3 = `() `, space is before ret_string.
2637 let overhead = if ret_str_len == 0 { 2 } else { 3 };
2638 let mut used_space = indent.width() + result.len() + ret_str_len + overhead;
2639 match fn_brace_style {
2640 FnBraceStyle::None => used_space += 1, // 1 = `;`
2641 FnBraceStyle::SameLine => used_space += 2, // 2 = `{}`
2642 FnBraceStyle::NextLine => (),
2644 let one_line_budget = context.budget(used_space);
2646 if one_line_budget > 0 {
2648 let (indent, multi_line_budget) = match context.config.indent_style() {
2649 IndentStyle::Block => {
2650 let indent = indent.block_indent(context.config);
2651 (indent, context.budget(indent.width() + 1))
2653 IndentStyle::Visual => {
2654 let indent = indent + result.len() + 1;
2655 let multi_line_overhead = match fn_brace_style {
2656 FnBraceStyle::SameLine => 4,
2659 (indent, context.budget(multi_line_overhead))
2663 return Some((one_line_budget, multi_line_budget, indent));
2667 // Didn't work. we must force vertical layout and put params on a newline.
2668 let new_indent = indent.block_indent(context.config);
2669 let used_space = match context.config.indent_style() {
2671 IndentStyle::Block => new_indent.width() + 1,
2672 // Account for `)` and possibly ` {`.
2673 IndentStyle::Visual => new_indent.width() + if ret_str_len == 0 { 1 } else { 3 },
2675 Some((0, context.budget(used_space), new_indent))
2678 fn newline_for_brace(config: &Config, where_clause: &ast::WhereClause) -> FnBraceStyle {
2679 let predicate_count = where_clause.predicates.len();
2681 if config.where_single_line() && predicate_count == 1 {
2682 return FnBraceStyle::SameLine;
2684 let brace_style = config.brace_style();
2686 let use_next_line = brace_style == BraceStyle::AlwaysNextLine
2687 || (brace_style == BraceStyle::SameLineWhere && predicate_count > 0);
2689 FnBraceStyle::NextLine
2691 FnBraceStyle::SameLine
2695 fn rewrite_generics(
2696 context: &RewriteContext<'_>,
2698 generics: &ast::Generics,
2700 ) -> Option<String> {
2701 // FIXME: convert bounds to where-clauses where they get too big or if
2702 // there is a where-clause at all.
2704 if generics.params.is_empty() {
2705 return Some(ident.to_owned());
2708 let params = generics.params.iter();
2709 overflow::rewrite_with_angle_brackets(context, ident, params, shape, generics.span)
2712 fn generics_shape_from_config(config: &Config, shape: Shape, offset: usize) -> Option<Shape> {
2713 match config.indent_style() {
2714 IndentStyle::Visual => shape.visual_indent(1 + offset).sub_width(offset + 2),
2715 IndentStyle::Block => {
2719 .block_indent(config.tab_spaces())
2720 .with_max_width(config)
2726 fn rewrite_where_clause_rfc_style(
2727 context: &RewriteContext<'_>,
2728 predicates: &[ast::WherePredicate],
2732 span_end: Option<BytePos>,
2733 span_end_before_where: BytePos,
2734 where_clause_option: WhereClauseOption,
2735 ) -> Option<String> {
2736 let (where_keyword, allow_single_line) = rewrite_where_keyword(
2741 span_end_before_where,
2742 where_clause_option,
2746 let clause_shape = shape
2748 .with_max_width(context.config)
2749 .block_left(context.config.tab_spaces())?
2751 let force_single_line = context.config.where_single_line()
2752 && predicates.len() == 1
2753 && !where_clause_option.veto_single_line;
2755 let preds_str = rewrite_bounds_on_where_clause(
2761 where_clause_option,
2767 if allow_single_line && !preds_str.contains('\n') && 6 + preds_str.len() <= shape.width
2768 || force_single_line
2772 clause_shape.indent.to_string_with_newline(context.config)
2775 Some(format!("{}{}{}", where_keyword, clause_sep, preds_str))
2778 /// Rewrite `where` and comment around it.
2779 fn rewrite_where_keyword(
2780 context: &RewriteContext<'_>,
2781 predicates: &[ast::WherePredicate],
2784 span_end_before_where: BytePos,
2785 where_clause_option: WhereClauseOption,
2786 ) -> Option<(String, bool)> {
2787 let block_shape = shape.block().with_max_width(context.config);
2789 let clause_shape = block_shape
2790 .block_left(context.config.tab_spaces())?
2793 let comment_separator = |comment: &str, shape: Shape| {
2794 if comment.is_empty() {
2797 shape.indent.to_string_with_newline(context.config)
2801 let (span_before, span_after) =
2802 missing_span_before_after_where(span_end_before_where, predicates, where_span);
2803 let (comment_before, comment_after) =
2804 rewrite_comments_before_after_where(context, span_before, span_after, shape)?;
2806 let starting_newline = match where_clause_option.snuggle {
2807 WhereClauseSpace::Space if comment_before.is_empty() => Cow::from(" "),
2808 WhereClauseSpace::None => Cow::from(""),
2809 _ => block_shape.indent.to_string_with_newline(context.config),
2812 let newline_before_where = comment_separator(&comment_before, shape);
2813 let newline_after_where = comment_separator(&comment_after, clause_shape);
2814 let result = format!(
2816 starting_newline, comment_before, newline_before_where, newline_after_where, comment_after
2818 let allow_single_line = where_clause_option.allow_single_line
2819 && comment_before.is_empty()
2820 && comment_after.is_empty();
2822 Some((result, allow_single_line))
2825 /// Rewrite bounds on a where clause.
2826 fn rewrite_bounds_on_where_clause(
2827 context: &RewriteContext<'_>,
2828 predicates: &[ast::WherePredicate],
2831 span_end: Option<BytePos>,
2832 where_clause_option: WhereClauseOption,
2833 force_single_line: bool,
2834 ) -> Option<String> {
2835 let span_start = predicates[0].span().lo();
2836 // If we don't have the start of the next span, then use the end of the
2837 // predicates, but that means we miss comments.
2838 let len = predicates.len();
2839 let end_of_preds = predicates[len - 1].span().hi();
2840 let span_end = span_end.unwrap_or(end_of_preds);
2841 let items = itemize_list(
2842 context.snippet_provider,
2846 |pred| pred.span().lo(),
2847 |pred| pred.span().hi(),
2848 |pred| pred.rewrite(context, shape),
2853 let comma_tactic = if where_clause_option.suppress_comma || force_single_line {
2854 SeparatorTactic::Never
2856 context.config.trailing_comma()
2859 // shape should be vertical only and only if we have `force_single_line` option enabled
2860 // and the number of items of the where-clause is equal to 1
2861 let shape_tactic = if force_single_line {
2862 DefinitiveListTactic::Horizontal
2864 DefinitiveListTactic::Vertical
2867 let fmt = ListFormatting::new(shape, context.config)
2868 .tactic(shape_tactic)
2869 .trailing_separator(comma_tactic)
2870 .preserve_newline(true);
2871 write_list(&items.collect::<Vec<_>>(), &fmt)
2874 fn rewrite_where_clause(
2875 context: &RewriteContext<'_>,
2876 predicates: &[ast::WherePredicate],
2878 brace_style: BraceStyle,
2882 span_end: Option<BytePos>,
2883 span_end_before_where: BytePos,
2884 where_clause_option: WhereClauseOption,
2885 ) -> Option<String> {
2886 if predicates.is_empty() {
2887 return Some(String::new());
2890 if context.config.indent_style() == IndentStyle::Block {
2891 return rewrite_where_clause_rfc_style(
2898 span_end_before_where,
2899 where_clause_option,
2903 let extra_indent = Indent::new(context.config.tab_spaces(), 0);
2905 let offset = match context.config.indent_style() {
2906 IndentStyle::Block => shape.indent + extra_indent.block_indent(context.config),
2907 // 6 = "where ".len()
2908 IndentStyle::Visual => shape.indent + extra_indent + 6,
2910 // FIXME: if indent_style != Visual, then the budgets below might
2911 // be out by a char or two.
2913 let budget = context.config.max_width() - offset.width();
2914 let span_start = predicates[0].span().lo();
2915 // If we don't have the start of the next span, then use the end of the
2916 // predicates, but that means we miss comments.
2917 let len = predicates.len();
2918 let end_of_preds = predicates[len - 1].span().hi();
2919 let span_end = span_end.unwrap_or(end_of_preds);
2920 let items = itemize_list(
2921 context.snippet_provider,
2925 |pred| pred.span().lo(),
2926 |pred| pred.span().hi(),
2927 |pred| pred.rewrite(context, Shape::legacy(budget, offset)),
2932 let item_vec = items.collect::<Vec<_>>();
2933 // FIXME: we don't need to collect here
2934 let tactic = definitive_tactic(&item_vec, ListTactic::Vertical, Separator::Comma, budget);
2936 let mut comma_tactic = context.config.trailing_comma();
2937 // Kind of a hack because we don't usually have trailing commas in where-clauses.
2938 if comma_tactic == SeparatorTactic::Vertical || where_clause_option.suppress_comma {
2939 comma_tactic = SeparatorTactic::Never;
2942 let fmt = ListFormatting::new(Shape::legacy(budget, offset), context.config)
2944 .trailing_separator(comma_tactic)
2945 .ends_with_newline(tactic.ends_with_newline(context.config.indent_style()))
2946 .preserve_newline(true);
2947 let preds_str = write_list(&item_vec, &fmt)?;
2949 let end_length = if terminator == "{" {
2950 // If the brace is on the next line we don't need to count it otherwise it needs two
2953 BraceStyle::AlwaysNextLine | BraceStyle::SameLineWhere => 0,
2954 BraceStyle::PreferSameLine => 2,
2956 } else if terminator == "=" {
2962 || preds_str.contains('\n')
2963 || shape.indent.width() + " where ".len() + preds_str.len() + end_length > shape.width
2967 (shape.indent + extra_indent).to_string(context.config),
2971 Some(format!(" where {}", preds_str))
2975 fn missing_span_before_after_where(
2976 before_item_span_end: BytePos,
2977 predicates: &[ast::WherePredicate],
2980 let missing_span_before = mk_sp(before_item_span_end, where_span.lo());
2982 let pos_after_where = where_span.lo() + BytePos(5);
2983 let missing_span_after = mk_sp(pos_after_where, predicates[0].span().lo());
2984 (missing_span_before, missing_span_after)
2987 fn rewrite_comments_before_after_where(
2988 context: &RewriteContext<'_>,
2989 span_before_where: Span,
2990 span_after_where: Span,
2992 ) -> Option<(String, String)> {
2993 let before_comment = rewrite_missing_comment(span_before_where, shape, context)?;
2994 let after_comment = rewrite_missing_comment(
2996 shape.block_indent(context.config.tab_spaces()),
2999 Some((before_comment, after_comment))
3003 context: &RewriteContext<'_>,
3005 ident: symbol::Ident,
3006 vis: &ast::Visibility,
3009 let mut result = String::with_capacity(128);
3010 let shape = Shape::indented(offset, context.config);
3012 result.push_str(format_visibility(context, vis).trim());
3014 // Check for a missing comment between the visibility and the item name.
3015 let after_vis = vis.span.hi();
3016 if let Some(before_item_name) = context
3018 .opt_span_before(mk_sp(vis.span.lo(), ident.span.hi()), item_name.trim())
3020 let missing_span = mk_sp(after_vis, before_item_name);
3021 if let Some(result_with_comment) = combine_strs_with_missing_comments(
3027 /* allow_extend */ true,
3029 result = result_with_comment;
3033 result.push_str(rewrite_ident(context, ident));
3038 #[derive(PartialEq, Eq, Clone, Copy)]
3046 context: &RewriteContext<'_>,
3047 generics: &ast::Generics,
3048 brace_style: BraceStyle,
3049 brace_pos: BracePos,
3053 ) -> Option<String> {
3054 let shape = Shape::legacy(context.budget(used_width + offset.width()), offset);
3055 let mut result = rewrite_generics(context, "", generics, shape)?;
3057 // If the generics are not parameterized then generics.span.hi() == 0,
3058 // so we use span.lo(), which is the position after `struct Foo`.
3059 let span_end_before_where = if !generics.params.is_empty() {
3064 let (same_line_brace, missed_comments) = if !generics.where_clause.predicates.is_empty() {
3065 let budget = context.budget(last_line_used_width(&result, offset.width()));
3066 let mut option = WhereClauseOption::snuggled(&result);
3067 if brace_pos == BracePos::None {
3068 option.suppress_comma = true;
3070 let where_clause_str = rewrite_where_clause(
3072 &generics.where_clause.predicates,
3073 generics.where_clause.span,
3075 Shape::legacy(budget, offset.block_only()),
3079 span_end_before_where,
3082 result.push_str(&where_clause_str);
3084 brace_pos == BracePos::ForceSameLine || brace_style == BraceStyle::PreferSameLine,
3085 // missed comments are taken care of in #rewrite_where_clause
3090 brace_pos == BracePos::ForceSameLine
3091 || (result.contains('\n') && brace_style == BraceStyle::PreferSameLine
3092 || brace_style != BraceStyle::AlwaysNextLine)
3093 || trimmed_last_line_width(&result) == 1,
3094 rewrite_missing_comment(
3096 span_end_before_where,
3097 if brace_pos == BracePos::None {
3100 context.snippet_provider.span_before(span, "{")
3108 // add missing comments
3109 let missed_line_comments = missed_comments
3110 .filter(|missed_comments| !missed_comments.is_empty())
3111 .map_or(false, |missed_comments| {
3112 let is_block = is_last_comment_block(&missed_comments);
3113 let sep = if is_block { " " } else { "\n" };
3114 result.push_str(sep);
3115 result.push_str(&missed_comments);
3118 if brace_pos == BracePos::None {
3119 return Some(result);
3121 let total_used_width = last_line_used_width(&result, used_width);
3122 let remaining_budget = context.budget(total_used_width);
3123 // If the same line brace if forced, it indicates that we are rewriting an item with empty body,
3124 // and hence we take the closer into account as well for one line budget.
3125 // We assume that the closer has the same length as the opener.
3126 let overhead = if brace_pos == BracePos::ForceSameLine {
3133 let forbid_same_line_brace = missed_line_comments || overhead > remaining_budget;
3134 if !forbid_same_line_brace && same_line_brace {
3138 result.push_str(&offset.block_only().to_string(context.config));
3145 impl Rewrite for ast::ForeignItem {
3146 fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
3147 let attrs_str = self.attrs.rewrite(context, shape)?;
3148 // Drop semicolon or it will be interpreted as comment.
3149 // FIXME: this may be a faulty span from libsyntax.
3150 let span = mk_sp(self.span.lo(), self.span.hi() - BytePos(1));
3152 let item_str = match self.kind {
3153 ast::ForeignItemKind::Fn(ref fn_kind) => {
3160 if let Some(ref body) = body {
3161 let mut visitor = FmtVisitor::from_context(context);
3162 visitor.block_indent = shape.indent;
3163 visitor.last_pos = self.span.lo();
3164 let inner_attrs = inner_attributes(&self.attrs);
3165 let fn_ctxt = visit::FnCtxt::Foreign;
3167 visit::FnKind::Fn(fn_ctxt, self.ident, sig, &self.vis, Some(body)),
3174 Some(visitor.buffer.to_owned())
3180 &FnSig::from_method_sig(sig, generics, &self.vis),
3184 .map(|(s, _, _)| format!("{};", s))
3187 ast::ForeignItemKind::Static(ref ty, mutability, _) => {
3188 // FIXME(#21): we're dropping potential comments in between the
3189 // function kw here.
3190 let vis = format_visibility(context, &self.vis);
3191 let mut_str = format_mutability(mutability);
3192 let prefix = format!(
3196 rewrite_ident(context, self.ident)
3204 shape.sub_width(1)?,
3208 ast::ForeignItemKind::TyAlias(ref ty_alias) => {
3209 let (kind, span) = (&ItemVisitorKind::ForeignItem(self), self.span);
3210 rewrite_type_alias(ty_alias, context, shape.indent, kind, span)
3212 ast::ForeignItemKind::MacCall(ref mac) => {
3213 rewrite_macro(mac, None, context, shape, MacroPosition::Item)
3217 let missing_span = if self.attrs.is_empty() {
3218 mk_sp(self.span.lo(), self.span.lo())
3220 mk_sp(self.attrs[self.attrs.len() - 1].span.hi(), self.span.lo())
3222 combine_strs_with_missing_comments(
3233 /// Rewrite the attributes of an item.
3235 context: &RewriteContext<'_>,
3239 ) -> Option<String> {
3240 let attrs = filter_inline_attrs(&item.attrs, item.span());
3241 let attrs_str = attrs.rewrite(context, shape)?;
3243 let missed_span = if attrs.is_empty() {
3244 mk_sp(item.span.lo(), item.span.lo())
3246 mk_sp(attrs[attrs.len() - 1].span.hi(), item.span.lo())
3249 let allow_extend = if attrs.len() == 1 {
3250 let line_len = attrs_str.len() + 1 + item_str.len();
3251 !attrs.first().unwrap().is_doc_comment()
3252 && context.config.inline_attribute_width() >= line_len
3257 combine_strs_with_missing_comments(
3267 /// Rewrite an inline mod.
3268 /// The given shape is used to format the mod's attributes.
3269 pub(crate) fn rewrite_mod(
3270 context: &RewriteContext<'_>,
3273 ) -> Option<String> {
3274 let mut result = String::with_capacity(32);
3275 result.push_str(&*format_visibility(context, &item.vis));
3276 result.push_str("mod ");
3277 result.push_str(rewrite_ident(context, item.ident));
3279 rewrite_attrs(context, item, &result, attrs_shape)
3282 /// Rewrite `extern crate foo;`.
3283 /// The given shape is used to format the extern crate's attributes.
3284 pub(crate) fn rewrite_extern_crate(
3285 context: &RewriteContext<'_>,
3288 ) -> Option<String> {
3289 assert!(is_extern_crate(item));
3290 let new_str = context.snippet(item.span);
3291 let item_str = if contains_comment(new_str) {
3294 let no_whitespace = &new_str.split_whitespace().collect::<Vec<&str>>().join(" ");
3295 String::from(&*Regex::new(r"\s;").unwrap().replace(no_whitespace, ";"))
3297 rewrite_attrs(context, item, &item_str, attrs_shape)
3300 /// Returns `true` for `mod foo;`, false for `mod foo { .. }`.
3301 pub(crate) fn is_mod_decl(item: &ast::Item) -> bool {
3304 ast::ItemKind::Mod(_, ast::ModKind::Loaded(_, ast::Inline::Yes, _))
3308 pub(crate) fn is_use_item(item: &ast::Item) -> bool {
3309 matches!(item.kind, ast::ItemKind::Use(_))
3312 pub(crate) fn is_extern_crate(item: &ast::Item) -> bool {
3313 matches!(item.kind, ast::ItemKind::ExternCrate(..))