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allow try as scrutinee, e.g. match try ...
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lcnr committed Apr 14, 2020
1 parent 2765f42 commit 81a3cd7
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Showing 7 changed files with 88 additions and 20 deletions.
8 changes: 3 additions & 5 deletions src/librustc_parse/parser/expr.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1846,11 +1846,9 @@ impl<'a> Parser<'a> {
}

fn is_try_block(&self) -> bool {
self.token.is_keyword(kw::Try) &&
self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace)) &&
self.token.uninterpolated_span().rust_2018() &&
// Prevent `while try {} {}`, `if try {} {} else {}`, etc.
!self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
self.token.is_keyword(kw::Try)
&& self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace))
&& self.token.uninterpolated_span().rust_2018()
}

/// Parses an `async move? {...}` expression.
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6 changes: 5 additions & 1 deletion src/test/ui/try-block/try-block-in-match.rs
Original file line number Diff line number Diff line change
@@ -1,7 +1,11 @@
// run-pass
// compile-flags: --edition 2018

#![feature(try_blocks)]

fn main() {
match try { false } { _ => {} } //~ ERROR expected expression, found reserved keyword `try`
match try { } {
Err(()) => (),
Ok(()) => (),
}
}
10 changes: 0 additions & 10 deletions src/test/ui/try-block/try-block-in-match.stderr

This file was deleted.

3 changes: 2 additions & 1 deletion src/test/ui/try-block/try-block-in-while.rs
Original file line number Diff line number Diff line change
Expand Up @@ -3,5 +3,6 @@
#![feature(try_blocks)]

fn main() {
while try { false } {} //~ ERROR expected expression, found reserved keyword `try`
while try { false } {}
//~^ ERROR the trait bound `bool: std::ops::Try` is not satisfied
}
9 changes: 6 additions & 3 deletions src/test/ui/try-block/try-block-in-while.stderr
Original file line number Diff line number Diff line change
@@ -1,8 +1,11 @@
error: expected expression, found reserved keyword `try`
--> $DIR/try-block-in-while.rs:6:11
error[E0277]: the trait bound `bool: std::ops::Try` is not satisfied
--> $DIR/try-block-in-while.rs:6:15
|
LL | while try { false } {}
| ^^^ expected expression
| ^^^^^^^^^ the trait `std::ops::Try` is not implemented for `bool`
|
= note: required by `std::ops::Try::from_ok`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0277`.
28 changes: 28 additions & 0 deletions src/test/ui/try-block/try-block-unused-delims.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,28 @@
// check-pass
// compile-flags: --edition 2018

#![feature(try_blocks)]
#![warn(unused_parens, unused_braces)]

fn consume<T>(_: Result<T, T>) -> T { todo!() }

fn main() {
consume((try {}));
//~^ WARN unnecessary parentheses

consume({ try {} });
//~^ WARN unnecessary braces

match (try {}) {
//~^ WARN unnecessary parentheses
Ok(()) | Err(()) => (),
}

if let Err(()) = (try {}) {}
//~^ WARN unnecessary parentheses

match (try {}) {
//~^ WARN unnecessary parentheses
Ok(()) | Err(()) => (),
}
}
44 changes: 44 additions & 0 deletions src/test/ui/try-block/try-block-unused-delims.stderr
Original file line number Diff line number Diff line change
@@ -0,0 +1,44 @@
warning: unnecessary parentheses around function argument
--> $DIR/try-block-unused-delims.rs:10:13
|
LL | consume((try {}));
| ^^^^^^^^ help: remove these parentheses
|
note: the lint level is defined here
--> $DIR/try-block-unused-delims.rs:5:9
|
LL | #![warn(unused_parens, unused_braces)]
| ^^^^^^^^^^^^^

warning: unnecessary braces around function argument
--> $DIR/try-block-unused-delims.rs:13:13
|
LL | consume({ try {} });
| ^^^^^^^^^^ help: remove these braces
|
note: the lint level is defined here
--> $DIR/try-block-unused-delims.rs:5:24
|
LL | #![warn(unused_parens, unused_braces)]
| ^^^^^^^^^^^^^

warning: unnecessary parentheses around `match` scrutinee expression
--> $DIR/try-block-unused-delims.rs:16:11
|
LL | match (try {}) {
| ^^^^^^^^ help: remove these parentheses

warning: unnecessary parentheses around `let` scrutinee expression
--> $DIR/try-block-unused-delims.rs:21:22
|
LL | if let Err(()) = (try {}) {}
| ^^^^^^^^ help: remove these parentheses

warning: unnecessary parentheses around `match` scrutinee expression
--> $DIR/try-block-unused-delims.rs:24:11
|
LL | match (try {}) {
| ^^^^^^^^ help: remove these parentheses

warning: 5 warnings emitted

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