1 // Copyright 2017 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 use syntax::{ast, ptr};
12 use syntax::codemap::Span;
13 use syntax::parse::classify;
15 use codemap::SpanUtils;
16 use expr::{block_contains_comment, is_simple_block, is_unsafe_block, rewrite_cond, ToExpr};
17 use items::{span_hi_for_arg, span_lo_for_arg};
18 use lists::{definitive_tactic, itemize_list, write_list, DefinitiveListTactic, ListFormatting,
19 ListTactic, Separator, SeparatorPlace, SeparatorTactic};
20 use rewrite::{Rewrite, RewriteContext};
22 use utils::{last_line_width, left_most_sub_expr, stmt_expr};
24 // This module is pretty messy because of the rules around closures and blocks:
25 // FIXME - the below is probably no longer true in full.
26 // * if there is a return type, then there must be braces,
27 // * given a closure with braces, whether that is parsed to give an inner block
28 // or not depends on if there is a return type and if there are statements
30 // * if the first expression in the body ends with a block (i.e., is a
31 // statement without needing a semi-colon), then adding or removing braces
32 // can change whether it is treated as an expression or statement.
35 pub fn rewrite_closure(
36 capture: ast::CaptureBy,
37 fn_decl: &ast::FnDecl,
40 context: &RewriteContext,
43 debug!("rewrite_closure {:?}", body);
45 let (prefix, extra_offset) =
46 rewrite_closure_fn_decl(capture, fn_decl, body, span, context, shape)?;
47 // 1 = space between `|...|` and body.
48 let body_shape = shape.offset_left(extra_offset)?;
50 if let ast::ExprKind::Block(ref block) = body.node {
51 // The body of the closure is an empty block.
52 if block.stmts.is_empty() && !block_contains_comment(block, context.codemap) {
53 return Some(format!("{} {{}}", prefix));
56 let result = match fn_decl.output {
57 ast::FunctionRetTy::Default(_) => {
58 try_rewrite_without_block(body, &prefix, context, shape, body_shape)
64 // Either we require a block, or tried without and failed.
65 rewrite_closure_block(block, &prefix, context, body_shape)
68 rewrite_closure_expr(body, &prefix, context, body_shape).or_else(|| {
69 // The closure originally had a non-block expression, but we can't fit on
70 // one line, so we'll insert a block.
71 rewrite_closure_with_block(body, &prefix, context, body_shape)
76 fn try_rewrite_without_block(
79 context: &RewriteContext,
83 let expr = get_inner_expr(expr, prefix, context);
85 if is_block_closure_forced(expr) {
86 rewrite_closure_with_block(expr, prefix, context, shape)
88 rewrite_closure_expr(expr, prefix, context, body_shape)
92 fn get_inner_expr<'a>(
95 context: &RewriteContext,
97 if let ast::ExprKind::Block(ref block) = expr.node {
98 if !needs_block(block, prefix, context) {
99 // block.stmts.len() == 1
100 if let Some(expr) = stmt_expr(&block.stmts[0]) {
101 return get_inner_expr(expr, prefix, context);
109 // Figure out if a block is necessary.
110 fn needs_block(block: &ast::Block, prefix: &str, context: &RewriteContext) -> bool {
111 is_unsafe_block(block) || block.stmts.len() > 1 || context.inside_macro
112 || block_contains_comment(block, context.codemap) || prefix.contains('\n')
115 // Rewrite closure with a single expression wrapping its body with block.
116 fn rewrite_closure_with_block(
119 context: &RewriteContext,
121 ) -> Option<String> {
122 let block = ast::Block {
125 id: ast::NodeId::new(0),
126 node: ast::StmtKind::Expr(ptr::P(body.clone())),
130 id: ast::NodeId::new(0),
131 rules: ast::BlockCheckMode::Default,
134 rewrite_closure_block(&block, prefix, context, shape)
137 // Rewrite closure with a single expression without wrapping its body with block.
138 fn rewrite_closure_expr(
141 context: &RewriteContext,
143 ) -> Option<String> {
144 let mut rewrite = expr.rewrite(context, shape);
145 if classify::expr_requires_semi_to_be_stmt(left_most_sub_expr(expr)) {
146 rewrite = and_one_line(rewrite);
148 rewrite = rewrite.and_then(|rw| {
149 if context.config.multiline_closure_forces_block() && rw.contains('\n') {
155 rewrite.map(|rw| format!("{} {}", prefix, rw))
158 // Rewrite closure whose body is block.
159 fn rewrite_closure_block(
162 context: &RewriteContext,
164 ) -> Option<String> {
165 let block_shape = shape.block();
166 let block_str = block.rewrite(context, block_shape)?;
167 Some(format!("{} {}", prefix, block_str))
170 // Return type is (prefix, extra_offset)
171 fn rewrite_closure_fn_decl(
172 capture: ast::CaptureBy,
173 fn_decl: &ast::FnDecl,
176 context: &RewriteContext,
178 ) -> Option<(String, usize)> {
179 let mover = if capture == ast::CaptureBy::Value {
184 // 4 = "|| {".len(), which is overconservative when the closure consists of
185 // a single expression.
186 let nested_shape = shape.shrink_left(mover.len())?.sub_width(4)?;
189 let argument_offset = nested_shape.indent + 1;
190 let arg_shape = nested_shape.offset_left(1)?.visual_indent(0);
191 let ret_str = fn_decl.output.rewrite(context, arg_shape)?;
193 let arg_items = itemize_list(
195 fn_decl.inputs.iter(),
197 |arg| span_lo_for_arg(arg),
198 |arg| span_hi_for_arg(context, arg),
199 |arg| arg.rewrite(context, arg_shape),
200 context.codemap.span_after(span, "|"),
204 let item_vec = arg_items.collect::<Vec<_>>();
205 // 1 = space between arguments and return type.
206 let horizontal_budget = nested_shape
208 .checked_sub(ret_str.len() + 1)
210 let tactic = definitive_tactic(
212 ListTactic::HorizontalVertical,
216 let arg_shape = match tactic {
217 DefinitiveListTactic::Horizontal => arg_shape.sub_width(ret_str.len() + 1)?,
221 let fmt = ListFormatting {
224 trailing_separator: SeparatorTactic::Never,
225 separator_place: SeparatorPlace::Back,
227 ends_with_newline: false,
228 preserve_newline: true,
229 config: context.config,
231 let list_str = write_list(&item_vec, &fmt)?;
232 let mut prefix = format!("{}|{}|", mover, list_str);
234 if !ret_str.is_empty() {
235 if prefix.contains('\n') {
237 prefix.push_str(&argument_offset.to_string(context.config));
241 prefix.push_str(&ret_str);
243 // 1 = space between `|...|` and body.
244 let extra_offset = last_line_width(&prefix) + 1;
246 Some((prefix, extra_offset))
249 // Rewriting closure which is placed at the end of the function call's arg.
250 // Returns `None` if the reformatted closure 'looks bad'.
251 pub fn rewrite_last_closure(
252 context: &RewriteContext,
255 ) -> Option<String> {
256 if let ast::ExprKind::Closure(capture, ref fn_decl, ref body, _) = expr.node {
257 let body = match body.node {
258 ast::ExprKind::Block(ref block) if is_simple_block(block, context.codemap) => {
259 stmt_expr(&block.stmts[0]).unwrap_or(body)
263 let (prefix, extra_offset) =
264 rewrite_closure_fn_decl(capture, fn_decl, body, expr.span, context, shape)?;
265 // If the closure goes multi line before its body, do not overflow the closure.
266 if prefix.contains('\n') {
269 // If we are inside macro, we do not want to add or remove block from closure body.
270 if context.inside_macro {
271 return expr.rewrite(context, shape);
274 let body_shape = shape.offset_left(extra_offset)?;
276 // We force to use block for the body of the closure for certain kinds of expressions.
277 if is_block_closure_forced(body) {
278 return rewrite_closure_with_block(body, &prefix, context, body_shape).and_then(
280 // If the expression can fit in a single line, we need not force block closure.
281 if body_str.lines().count() <= 7 {
282 match rewrite_closure_expr(body, &prefix, context, shape) {
283 Some(ref single_line_body_str)
284 if !single_line_body_str.contains('\n') =>
286 Some(single_line_body_str.clone())
297 // When overflowing the closure which consists of a single control flow expression,
298 // force to use block if its condition uses multi line.
299 let is_multi_lined_cond = rewrite_cond(context, body, body_shape)
300 .map(|cond| cond.contains('\n') || cond.len() > body_shape.width)
302 if is_multi_lined_cond {
303 return rewrite_closure_with_block(body, &prefix, context, body_shape);
306 // Seems fine, just format the closure in usual manner.
307 return expr.rewrite(context, shape);
312 /// Returns true if the given vector of arguments has more than one `ast::ExprKind::Closure`.
313 pub fn args_have_many_closure<T>(args: &[&T]) -> bool
320 .map(|e| match e.node {
321 ast::ExprKind::Closure(..) => true,
329 fn is_block_closure_forced(expr: &ast::Expr) -> bool {
331 ast::ExprKind::If(..) |
332 ast::ExprKind::IfLet(..) |
333 ast::ExprKind::Loop(..) |
334 ast::ExprKind::While(..) |
335 ast::ExprKind::WhileLet(..) |
336 ast::ExprKind::ForLoop(..) => true,
337 ast::ExprKind::AddrOf(_, ref expr) |
338 ast::ExprKind::Box(ref expr) |
339 ast::ExprKind::Try(ref expr) |
340 ast::ExprKind::Unary(_, ref expr) |
341 ast::ExprKind::Cast(ref expr, _) => is_block_closure_forced(expr),
346 fn and_one_line(x: Option<String>) -> Option<String> {
347 x.and_then(|x| if x.contains('\n') { None } else { Some(x) })