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Add a nicer error message for missing in for loop, fixes #40782. #45639

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Merged
merged 7 commits into from
Nov 4, 2017
Merged

Add a nicer error message for missing in for loop, fixes #40782. #45639

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6a62ea6
Add a nicer error message for missing in for loop, fixes #40782.
LaurentMazare Oct 30, 2017
6d060bd
Fix spans and error messages.
LaurentMazare Oct 31, 2017
531b7f2
Add some missing spaces.
LaurentMazare Oct 31, 2017
0d72853
Formatting tweak.
LaurentMazare Oct 31, 2017
175cfbf
Remove the parser snapshot hack.
LaurentMazare Nov 1, 2017
d336f02
Preserve original formatting.
LaurentMazare Nov 1, 2017
ed20f3b
Remove the redundant span_label.
LaurentMazare Nov 1, 2017
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9 changes: 8 additions & 1 deletion src/libsyntax/parse/parser.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -3154,7 +3154,14 @@ impl<'a> Parser<'a> {
// Parse: `for <src_pat> in <src_expr> <src_loop_block>`

let pat = self.parse_pat()?;
self.expect_keyword(keywords::In)?;
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This can be done in much simpler way without parser snapshots (please don't overuse the trick from #42578).

if !self.eat_keyword(keywords::In) {
    span_err(/*missing `in`*/) // Non-fatal error
}
let expr = self.parse_expr_res(...); // Then parse as usual as if `in` were written

if !self.eat_keyword(keywords::In) {
let in_span = self.prev_span.between(self.span);
let mut err = self.sess.span_diagnostic
.struct_span_err(in_span, "missing `in` in `for` loop");
err.span_label(in_span, "expected `in` here");
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Nit: The extra label here creates unnecessary duplication, IMO. The primary message already says that in is missing and the suggestion is already formatted as a label.

err.span_suggestion_short(in_span, "try adding `in` here", " in ".into());
err.emit();
}
let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
let (iattrs, loop_block) = self.parse_inner_attrs_and_block()?;
attrs.extend(iattrs);
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15 changes: 15 additions & 0 deletions src/test/ui/issue-40782.rs
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@@ -0,0 +1,15 @@
// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

fn main() {
for i 0..2 {
}
}

11 changes: 11 additions & 0 deletions src/test/ui/issue-40782.stderr
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@@ -0,0 +1,11 @@
error: missing `in` in `for` loop
--> $DIR/issue-40782.rs:12:10
|
12 | for i 0..2 {
| ^
| |
| expected `in` here
| help: try adding `in` here

error: aborting due to previous error