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 try_rewrite_without_block(block, fn_decl, &prefix, context, shape, body_shape).or_else(|| {
52 // Either we require a block, or tried without and failed.
53 rewrite_closure_block(block, &prefix, context, body_shape)
56 rewrite_closure_expr(body, &prefix, context, body_shape).or_else(|| {
57 // The closure originally had a non-block expression, but we can't fit on
58 // one line, so we'll insert a block.
59 rewrite_closure_with_block(body, &prefix, context, body_shape)
64 fn try_rewrite_without_block(
66 fn_decl: &ast::FnDecl,
68 context: &RewriteContext,
72 // The body of the closure is an empty block.
73 if block.stmts.is_empty() && !block_contains_comment(block, context.codemap) {
74 return Some(format!("{} {{}}", prefix));
77 match fn_decl.output {
78 ast::FunctionRetTy::Default(_) => {}
82 get_inner_expr(block, prefix, context).and_then(|expr| {
83 return if is_block_closure_forced(expr) {
84 rewrite_closure_with_block(expr, prefix, context, shape)
86 rewrite_closure_expr(expr, prefix, context, body_shape)
91 fn get_inner_expr<'a>(
92 block: &'a ast::Block,
94 context: &RewriteContext,
95 ) -> Option<&'a ast::Expr> {
96 if !needs_block(block, prefix, context) {
97 // block.stmts.len() == 1
98 stmt_expr(&block.stmts[0])
104 // Figure out if a block is necessary.
105 fn needs_block(block: &ast::Block, prefix: &str, context: &RewriteContext) -> bool {
106 is_unsafe_block(block) || block.stmts.len() > 1 || context.inside_macro
107 || block_contains_comment(block, context.codemap) || prefix.contains('\n')
110 // Rewrite closure with a single expression wrapping its body with block.
111 fn rewrite_closure_with_block(
114 context: &RewriteContext,
116 ) -> Option<String> {
117 let block = ast::Block {
120 id: ast::NodeId::new(0),
121 node: ast::StmtKind::Expr(ptr::P(body.clone())),
125 id: ast::NodeId::new(0),
126 rules: ast::BlockCheckMode::Default,
129 rewrite_closure_block(&block, prefix, context, shape)
132 // Rewrite closure with a single expression without wrapping its body with block.
133 fn rewrite_closure_expr(
136 context: &RewriteContext,
138 ) -> Option<String> {
139 let mut rewrite = expr.rewrite(context, shape);
140 if classify::expr_requires_semi_to_be_stmt(left_most_sub_expr(expr)) {
141 rewrite = and_one_line(rewrite);
143 rewrite = rewrite.and_then(|rw| {
144 if context.config.multiline_closure_forces_block() && rw.contains('\n') {
150 rewrite.map(|rw| format!("{} {}", prefix, rw))
153 // Rewrite closure whose body is block.
154 fn rewrite_closure_block(
157 context: &RewriteContext,
159 ) -> Option<String> {
160 let block_shape = shape.block();
161 let block_str = block.rewrite(context, block_shape)?;
162 Some(format!("{} {}", prefix, block_str))
165 // Return type is (prefix, extra_offset)
166 fn rewrite_closure_fn_decl(
167 capture: ast::CaptureBy,
168 fn_decl: &ast::FnDecl,
171 context: &RewriteContext,
173 ) -> Option<(String, usize)> {
174 let mover = if capture == ast::CaptureBy::Value {
179 // 4 = "|| {".len(), which is overconservative when the closure consists of
180 // a single expression.
181 let nested_shape = shape.shrink_left(mover.len())?.sub_width(4)?;
184 let argument_offset = nested_shape.indent + 1;
185 let arg_shape = nested_shape.offset_left(1)?.visual_indent(0);
186 let ret_str = fn_decl.output.rewrite(context, arg_shape)?;
188 let arg_items = itemize_list(
190 fn_decl.inputs.iter(),
192 |arg| span_lo_for_arg(arg),
193 |arg| span_hi_for_arg(context, arg),
194 |arg| arg.rewrite(context, arg_shape),
195 context.codemap.span_after(span, "|"),
199 let item_vec = arg_items.collect::<Vec<_>>();
200 // 1 = space between arguments and return type.
201 let horizontal_budget = nested_shape
203 .checked_sub(ret_str.len() + 1)
205 let tactic = definitive_tactic(
207 ListTactic::HorizontalVertical,
211 let arg_shape = match tactic {
212 DefinitiveListTactic::Horizontal => arg_shape.sub_width(ret_str.len() + 1)?,
216 let fmt = ListFormatting {
219 trailing_separator: SeparatorTactic::Never,
220 separator_place: SeparatorPlace::Back,
222 ends_with_newline: false,
223 preserve_newline: true,
224 config: context.config,
226 let list_str = write_list(&item_vec, &fmt)?;
227 let mut prefix = format!("{}|{}|", mover, list_str);
229 if !ret_str.is_empty() {
230 if prefix.contains('\n') {
232 prefix.push_str(&argument_offset.to_string(context.config));
236 prefix.push_str(&ret_str);
238 // 1 = space between `|...|` and body.
239 let extra_offset = last_line_width(&prefix) + 1;
241 Some((prefix, extra_offset))
244 // Rewriting closure which is placed at the end of the function call's arg.
245 // Returns `None` if the reformatted closure 'looks bad'.
246 pub fn rewrite_last_closure(
247 context: &RewriteContext,
250 ) -> Option<String> {
251 if let ast::ExprKind::Closure(capture, ref fn_decl, ref body, _) = expr.node {
252 let body = match body.node {
253 ast::ExprKind::Block(ref block) if is_simple_block(block, context.codemap) => {
254 stmt_expr(&block.stmts[0]).unwrap_or(body)
258 let (prefix, extra_offset) =
259 rewrite_closure_fn_decl(capture, fn_decl, body, expr.span, context, shape)?;
260 // If the closure goes multi line before its body, do not overflow the closure.
261 if prefix.contains('\n') {
264 // If we are inside macro, we do not want to add or remove block from closure body.
265 if context.inside_macro {
266 return expr.rewrite(context, shape);
269 let body_shape = shape.offset_left(extra_offset)?;
271 // We force to use block for the body of the closure for certain kinds of expressions.
272 if is_block_closure_forced(body) {
273 return rewrite_closure_with_block(body, &prefix, context, body_shape).and_then(
275 // If the expression can fit in a single line, we need not force block closure.
276 if body_str.lines().count() <= 7 {
277 match rewrite_closure_expr(body, &prefix, context, shape) {
278 Some(ref single_line_body_str)
279 if !single_line_body_str.contains('\n') =>
281 Some(single_line_body_str.clone())
292 // When overflowing the closure which consists of a single control flow expression,
293 // force to use block if its condition uses multi line.
294 let is_multi_lined_cond = rewrite_cond(context, body, body_shape)
295 .map(|cond| cond.contains('\n') || cond.len() > body_shape.width)
297 if is_multi_lined_cond {
298 return rewrite_closure_with_block(body, &prefix, context, body_shape);
301 // Seems fine, just format the closure in usual manner.
302 return expr.rewrite(context, shape);
307 /// Returns true if the given vector of arguments has more than one `ast::ExprKind::Closure`.
308 pub fn args_have_many_closure<T>(args: &[&T]) -> bool
315 .map(|e| match e.node {
316 ast::ExprKind::Closure(..) => true,
324 fn is_block_closure_forced(expr: &ast::Expr) -> bool {
326 ast::ExprKind::If(..) |
327 ast::ExprKind::IfLet(..) |
328 ast::ExprKind::Loop(..) |
329 ast::ExprKind::While(..) |
330 ast::ExprKind::WhileLet(..) |
331 ast::ExprKind::ForLoop(..) => true,
332 ast::ExprKind::AddrOf(_, ref expr) |
333 ast::ExprKind::Box(ref expr) |
334 ast::ExprKind::Try(ref expr) |
335 ast::ExprKind::Unary(_, ref expr) |
336 ast::ExprKind::Cast(ref expr, _) => is_block_closure_forced(expr),
341 fn and_one_line(x: Option<String>) -> Option<String> {
342 x.and_then(|x| if x.contains('\n') { None } else { Some(x) })