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Recover ternary expression as error
1 parent 041f031 commit e81a5c6

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3 files changed

+22
-139
lines changed

3 files changed

+22
-139
lines changed

‎compiler/rustc_parse/src/parser/diagnostics.rs

+11-9
Original file line numberDiff line numberDiff line change
@@ -504,8 +504,10 @@ impl<'a> Parser<'a> {
504504

505505
// Special-case "expected `;`" errors
506506
if expected.contains(&TokenType::Token(token::Semi)) {
507-
if self.prev_token == token::Question && self.maybe_recover_from_ternary_operator() {
508-
return Ok(true);
507+
// If the user is trying to write a ternary expression, recover it and
508+
// return an Err to prevent a cascade of irrelevant diagnostics
509+
if self.prev_token == token::Question && let Err(e) = self.maybe_recover_from_ternary_operator() {
510+
return Err(e);
509511
}
510512

511513
if self.token.span == DUMMY_SP || self.prev_token.span == DUMMY_SP {
@@ -1428,10 +1430,10 @@ impl<'a> Parser<'a> {
14281430

14291431
/// Rust has no ternary operator (`cond ? then : else`). Parse it and try
14301432
/// to recover from it if `then` and `else` are valid expressions. Returns
1431-
/// whether it was a ternary operator.
1432-
pub(super) fn maybe_recover_from_ternary_operator(&mut self) -> bool {
1433+
/// an err if this appears to be a ternary expression.
1434+
pub(super) fn maybe_recover_from_ternary_operator(&mut self) -> PResult<'a, ()> {
14331435
if self.prev_token != token::Question {
1434-
return false;
1436+
return PResult::Ok(());
14351437
}
14361438

14371439
let lo = self.prev_token.span.lo();
@@ -1449,8 +1451,9 @@ impl<'a> Parser<'a> {
14491451
if self.eat_noexpect(&token::Colon) {
14501452
match self.parse_expr() {
14511453
Ok(_) => {
1452-
self.sess.emit_err(TernaryOperator { span: self.token.span.with_lo(lo) });
1453-
return true;
1454+
return Err(self
1455+
.sess
1456+
.create_err(TernaryOperator { span: self.token.span.with_lo(lo) }));
14541457
}
14551458
Err(err) => {
14561459
err.cancel();
@@ -1459,8 +1462,7 @@ impl<'a> Parser<'a> {
14591462
}
14601463
}
14611464
self.restore_snapshot(snapshot);
1462-
1463-
false
1465+
Ok(())
14641466
}
14651467

14661468
pub(super) fn maybe_recover_from_bad_type_plus(&mut self, ty: &Ty) -> PResult<'a, ()> {

‎tests/ui/parser/ternary_operator.rs

+4-50
Original file line numberDiff line numberDiff line change
@@ -1,76 +1,30 @@
1-
// A good chunk of these errors aren't shown to the user, but are still
2-
// required in the test for it to pass.
3-
4-
fn a() { //~ NOTE this function should return `Result` or `Option` to accept `?`
1+
fn a() {
52
let x = 5 > 2 ? true : false;
63
//~^ ERROR Rust has no ternary operator
74
//~| HELP use an `if-else` expression instead
8-
//~| ERROR the `?` operator can only be applied to values that implement `Try` [E0277]
9-
//~| HELP the trait `Try` is not implemented for `{integer}`
10-
//~| ERROR the `?` operator can only be used in a function that returns `Result` or `Option` (or another type that implements `FromResidual`) [E0277]
11-
//~| HELP the trait `FromResidual<_>` is not implemented for `()`
12-
//~| NOTE in this expansion of desugaring of operator `?`
13-
//~| NOTE the `?` operator cannot be applied to type `{integer}`
14-
//~| NOTE in this expansion of desugaring of operator `?`
15-
//~| NOTE in this expansion of desugaring of operator `?`
16-
//~| NOTE cannot use the `?` operator in a function that returns `()`
17-
//~| NOTE in this expansion of desugaring of operator `?`
185
}
196

20-
fn b() { //~ NOTE this function should return `Result` or `Option` to accept `?`
7+
fn b() {
218
let x = 5 > 2 ? { true } : { false };
229
//~^ ERROR Rust has no ternary operator
2310
//~| HELP use an `if-else` expression instead
24-
//~| ERROR the `?` operator can only be applied to values that implement `Try` [E0277]
25-
//~| HELP the trait `Try` is not implemented for `{integer}`
26-
//~| ERROR the `?` operator can only be used in a function that returns `Result` or `Option` (or another type that implements `FromResidual`) [E0277]
27-
//~| HELP the trait `FromResidual<_>` is not implemented for `()`
28-
//~| NOTE in this expansion of desugaring of operator `?`
29-
//~| NOTE the `?` operator cannot be applied to type `{integer}`
30-
//~| NOTE in this expansion of desugaring of operator `?`
31-
//~| NOTE in this expansion of desugaring of operator `?`
32-
//~| NOTE cannot use the `?` operator in a function that returns `()`
33-
//~| NOTE in this expansion of desugaring of operator `?`
3411
}
3512

36-
fn c() { //~ NOTE this function should return `Result` or `Option` to accept `?`
13+
fn c() {
3714
let x = 5 > 2 ? f32::MAX : f32::MIN;
3815
//~^ ERROR Rust has no ternary operator
3916
//~| HELP use an `if-else` expression instead
40-
//~| ERROR the `?` operator can only be applied to values that implement `Try` [E0277]
41-
//~| HELP the trait `Try` is not implemented for `{integer}`
42-
//~| ERROR the `?` operator can only be used in a function that returns `Result` or `Option` (or another type that implements `FromResidual`) [E0277]
43-
//~| HELP the trait `FromResidual<_>` is not implemented for `()`
44-
//~| NOTE in this expansion of desugaring of operator `?`
45-
//~| NOTE the `?` operator cannot be applied to type `{integer}`
46-
//~| NOTE in this expansion of desugaring of operator `?`
47-
//~| NOTE in this expansion of desugaring of operator `?`
48-
//~| NOTE cannot use the `?` operator in a function that returns `()`
49-
//~| NOTE in this expansion of desugaring of operator `?`
5017
}
5118

5219
fn bad() {
5320
// regression test for #117208
5421
v ? return;
5522
//~^ ERROR expected one of
56-
//~| NOTE expected one of
5723
}
5824

59-
fn main() { //~ NOTE this function should return `Result` or `Option` to accept `?`
25+
fn main() {
6026
let x = 5 > 2 ? { let x = vec![]: Vec<u16>; x } : { false };
6127
//~^ ERROR Rust has no ternary operator
6228
//~| HELP use an `if-else` expression instead
6329
//~| ERROR expected one of `.`, `;`, `?`, `else`, or an operator, found `:`
64-
//~| NOTE expected one of `.`, `;`, `?`, `else`, or an operator
65-
//~| ERROR the `?` operator can only be applied to values that implement `Try` [E0277]
66-
//~| HELP the trait `Try` is not implemented for `{integer}`
67-
//~| ERROR the `?` operator can only be used in a function that returns `Result` or `Option` (or another type that implements `FromResidual`) [E0277]
68-
//~| HELP the trait `FromResidual<_>` is not implemented for `()`
69-
//~| NOTE type ascription syntax has been removed, see issue #101728 <https://github.com/rust-lang/rust/issues/101728>
70-
//~| NOTE in this expansion of desugaring of operator `?`
71-
//~| NOTE the `?` operator cannot be applied to type `{integer}`
72-
//~| NOTE in this expansion of desugaring of operator `?`
73-
//~| NOTE in this expansion of desugaring of operator `?`
74-
//~| NOTE cannot use the `?` operator in a function that returns `()`
75-
//~| NOTE in this expansion of desugaring of operator `?`
7630
}

‎tests/ui/parser/ternary_operator.stderr

+7-80
Original file line numberDiff line numberDiff line change
@@ -1,121 +1,48 @@
11
error: Rust has no ternary operator
2-
--> $DIR/ternary_operator.rs:5:19
2+
--> $DIR/ternary_operator.rs:2:19
33
|
44
LL | let x = 5 > 2 ? true : false;
55
| ^^^^^^^^^^^^^^^
66
|
77
= help: use an `if-else` expression instead
88

99
error: Rust has no ternary operator
10-
--> $DIR/ternary_operator.rs:21:19
10+
--> $DIR/ternary_operator.rs:8:19
1111
|
1212
LL | let x = 5 > 2 ? { true } : { false };
1313
| ^^^^^^^^^^^^^^^^^^^^^^^
1414
|
1515
= help: use an `if-else` expression instead
1616

1717
error: Rust has no ternary operator
18-
--> $DIR/ternary_operator.rs:37:19
18+
--> $DIR/ternary_operator.rs:14:19
1919
|
2020
LL | let x = 5 > 2 ? f32::MAX : f32::MIN;
2121
| ^^^^^^^^^^^^^^^^^^^^^^
2222
|
2323
= help: use an `if-else` expression instead
2424

2525
error: expected one of `.`, `;`, `?`, `}`, or an operator, found keyword `return`
26-
--> $DIR/ternary_operator.rs:54:9
26+
--> $DIR/ternary_operator.rs:21:9
2727
|
2828
LL | v ? return;
2929
| ^^^^^^ expected one of `.`, `;`, `?`, `}`, or an operator
3030

3131
error: expected one of `.`, `;`, `?`, `else`, or an operator, found `:`
32-
--> $DIR/ternary_operator.rs:60:37
32+
--> $DIR/ternary_operator.rs:26:37
3333
|
3434
LL | let x = 5 > 2 ? { let x = vec![]: Vec<u16>; x } : { false };
3535
| ^ expected one of `.`, `;`, `?`, `else`, or an operator
3636
|
3737
= note: type ascription syntax has been removed, see issue #101728 <https://github.com/rust-lang/rust/issues/101728>
3838

3939
error: Rust has no ternary operator
40-
--> $DIR/ternary_operator.rs:60:19
40+
--> $DIR/ternary_operator.rs:26:19
4141
|
4242
LL | let x = 5 > 2 ? { let x = vec![]: Vec<u16>; x } : { false };
4343
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
4444
|
4545
= help: use an `if-else` expression instead
4646

47-
error[E0277]: the `?` operator can only be applied to values that implement `Try`
48-
--> $DIR/ternary_operator.rs:5:17
49-
|
50-
LL | let x = 5 > 2 ? true : false;
51-
| ^^^ the `?` operator cannot be applied to type `{integer}`
52-
|
53-
= help: the trait `Try` is not implemented for `{integer}`
54-
55-
error[E0277]: the `?` operator can only be used in a function that returns `Result` or `Option` (or another type that implements `FromResidual`)
56-
--> $DIR/ternary_operator.rs:5:19
57-
|
58-
LL | fn a() {
59-
| ------ this function should return `Result` or `Option` to accept `?`
60-
LL | let x = 5 > 2 ? true : false;
61-
| ^ cannot use the `?` operator in a function that returns `()`
62-
|
63-
= help: the trait `FromResidual<_>` is not implemented for `()`
64-
65-
error[E0277]: the `?` operator can only be applied to values that implement `Try`
66-
--> $DIR/ternary_operator.rs:21:17
67-
|
68-
LL | let x = 5 > 2 ? { true } : { false };
69-
| ^^^ the `?` operator cannot be applied to type `{integer}`
70-
|
71-
= help: the trait `Try` is not implemented for `{integer}`
72-
73-
error[E0277]: the `?` operator can only be used in a function that returns `Result` or `Option` (or another type that implements `FromResidual`)
74-
--> $DIR/ternary_operator.rs:21:19
75-
|
76-
LL | fn b() {
77-
| ------ this function should return `Result` or `Option` to accept `?`
78-
LL | let x = 5 > 2 ? { true } : { false };
79-
| ^ cannot use the `?` operator in a function that returns `()`
80-
|
81-
= help: the trait `FromResidual<_>` is not implemented for `()`
82-
83-
error[E0277]: the `?` operator can only be applied to values that implement `Try`
84-
--> $DIR/ternary_operator.rs:37:17
85-
|
86-
LL | let x = 5 > 2 ? f32::MAX : f32::MIN;
87-
| ^^^ the `?` operator cannot be applied to type `{integer}`
88-
|
89-
= help: the trait `Try` is not implemented for `{integer}`
90-
91-
error[E0277]: the `?` operator can only be used in a function that returns `Result` or `Option` (or another type that implements `FromResidual`)
92-
--> $DIR/ternary_operator.rs:37:19
93-
|
94-
LL | fn c() {
95-
| ------ this function should return `Result` or `Option` to accept `?`
96-
LL | let x = 5 > 2 ? f32::MAX : f32::MIN;
97-
| ^ cannot use the `?` operator in a function that returns `()`
98-
|
99-
= help: the trait `FromResidual<_>` is not implemented for `()`
100-
101-
error[E0277]: the `?` operator can only be applied to values that implement `Try`
102-
--> $DIR/ternary_operator.rs:60:17
103-
|
104-
LL | let x = 5 > 2 ? { let x = vec![]: Vec<u16>; x } : { false };
105-
| ^^^ the `?` operator cannot be applied to type `{integer}`
106-
|
107-
= help: the trait `Try` is not implemented for `{integer}`
108-
109-
error[E0277]: the `?` operator can only be used in a function that returns `Result` or `Option` (or another type that implements `FromResidual`)
110-
--> $DIR/ternary_operator.rs:60:19
111-
|
112-
LL | fn main() {
113-
| --------- this function should return `Result` or `Option` to accept `?`
114-
LL | let x = 5 > 2 ? { let x = vec![]: Vec<u16>; x } : { false };
115-
| ^ cannot use the `?` operator in a function that returns `()`
116-
|
117-
= help: the trait `FromResidual<_>` is not implemented for `()`
118-
119-
error: aborting due to 14 previous errors
47+
error: aborting due to 6 previous errors
12048

121-
For more information about this error, try `rustc --explain E0277`.

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