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Recover ternary expression as error
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@clubby789
clubby789 committed Oct 26, 2023
1 parent 041f031 commit cddf088
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Showing 3 changed files with 24 additions and 139 deletions.
22 changes: 13 additions & 9 deletions compiler/rustc_parse/src/parser/diagnostics.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -34,7 +34,7 @@ use rustc_ast_pretty::pprust;
use rustc_data_structures::fx::FxHashSet;
use rustc_errors::{
pluralize, AddToDiagnostic, Applicability, Diagnostic, DiagnosticBuilder, DiagnosticMessage,
ErrorGuaranteed, FatalError, Handler, IntoDiagnostic, MultiSpan, PResult,
ErrorGuaranteed, FatalError, Handler, IntoDiagnostic, MultiSpan, PErr, PResult,
};
use rustc_session::errors::ExprParenthesesNeeded;
use rustc_span::source_map::Spanned;
Expand Down Expand Up @@ -504,8 +504,10 @@ impl<'a> Parser<'a> {

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

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

/// Rust has no ternary operator (`cond ? then : else`). Parse it and try
/// to recover from it if `then` and `else` are valid expressions. Returns
/// whether it was a ternary operator.
pub(super) fn maybe_recover_from_ternary_operator(&mut self) -> bool {
/// a [`PErr`] if this appears to be a ternary expression.
pub(super) fn maybe_recover_from_ternary_operator(&mut self) -> Option<PErr<'a>> {
if self.prev_token != token::Question {
return false;
return None;
}

let lo = self.prev_token.span.lo();
Expand All @@ -1449,8 +1451,10 @@ impl<'a> Parser<'a> {
if self.eat_noexpect(&token::Colon) {
match self.parse_expr() {
Ok(_) => {
self.sess.emit_err(TernaryOperator { span: self.token.span.with_lo(lo) });
return true;
return Some(
self.sess
.create_err(TernaryOperator { span: self.token.span.with_lo(lo) }),
);
}
Err(err) => {
err.cancel();
Expand All @@ -1460,7 +1464,7 @@ impl<'a> Parser<'a> {
}
self.restore_snapshot(snapshot);

false
None
}

pub(super) fn maybe_recover_from_bad_type_plus(&mut self, ty: &Ty) -> PResult<'a, ()> {
Expand Down
54 changes: 4 additions & 50 deletions tests/ui/parser/ternary_operator.rs
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Original file line number Diff line number Diff line change
@@ -1,76 +1,30 @@
// A good chunk of these errors aren't shown to the user, but are still
// required in the test for it to pass.

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

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

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

fn bad() {
// regression test for #117208
v ? return;
//~^ ERROR expected one of
//~| NOTE expected one of
}

fn main() { //~ NOTE this function should return `Result` or `Option` to accept `?`
fn main() {
let x = 5 > 2 ? { let x = vec![]: Vec<u16>; x } : { false };
//~^ ERROR Rust has no ternary operator
//~| HELP use an `if-else` expression instead
//~| ERROR expected one of `.`, `;`, `?`, `else`, or an operator, found `:`
//~| NOTE expected one of `.`, `;`, `?`, `else`, or an operator
//~| ERROR the `?` operator can only be applied to values that implement `Try` [E0277]
//~| HELP the trait `Try` is not implemented for `{integer}`
//~| ERROR the `?` operator can only be used in a function that returns `Result` or `Option` (or another type that implements `FromResidual`) [E0277]
//~| HELP the trait `FromResidual<_>` is not implemented for `()`
//~| NOTE type ascription syntax has been removed, see issue #101728 <https://github.com/rust-lang/rust/issues/101728>
//~| NOTE in this expansion of desugaring of operator `?`
//~| NOTE the `?` operator cannot be applied to type `{integer}`
//~| NOTE in this expansion of desugaring of operator `?`
//~| NOTE in this expansion of desugaring of operator `?`
//~| NOTE cannot use the `?` operator in a function that returns `()`
//~| NOTE in this expansion of desugaring of operator `?`
}
87 changes: 7 additions & 80 deletions tests/ui/parser/ternary_operator.stderr
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Original file line number Diff line number Diff line change
@@ -1,121 +1,48 @@
error: Rust has no ternary operator
--> $DIR/ternary_operator.rs:5:19
--> $DIR/ternary_operator.rs:2:19
|
LL | let x = 5 > 2 ? true : false;
| ^^^^^^^^^^^^^^^
|
= help: use an `if-else` expression instead

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

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

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

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

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

error[E0277]: the `?` operator can only be applied to values that implement `Try`
--> $DIR/ternary_operator.rs:5:17
|
LL | let x = 5 > 2 ? true : false;
| ^^^ the `?` operator cannot be applied to type `{integer}`
|
= help: the trait `Try` is not implemented for `{integer}`

error[E0277]: the `?` operator can only be used in a function that returns `Result` or `Option` (or another type that implements `FromResidual`)
--> $DIR/ternary_operator.rs:5:19
|
LL | fn a() {
| ------ this function should return `Result` or `Option` to accept `?`
LL | let x = 5 > 2 ? true : false;
| ^ cannot use the `?` operator in a function that returns `()`
|
= help: the trait `FromResidual<_>` is not implemented for `()`

error[E0277]: the `?` operator can only be applied to values that implement `Try`
--> $DIR/ternary_operator.rs:21:17
|
LL | let x = 5 > 2 ? { true } : { false };
| ^^^ the `?` operator cannot be applied to type `{integer}`
|
= help: the trait `Try` is not implemented for `{integer}`

error[E0277]: the `?` operator can only be used in a function that returns `Result` or `Option` (or another type that implements `FromResidual`)
--> $DIR/ternary_operator.rs:21:19
|
LL | fn b() {
| ------ this function should return `Result` or `Option` to accept `?`
LL | let x = 5 > 2 ? { true } : { false };
| ^ cannot use the `?` operator in a function that returns `()`
|
= help: the trait `FromResidual<_>` is not implemented for `()`

error[E0277]: the `?` operator can only be applied to values that implement `Try`
--> $DIR/ternary_operator.rs:37:17
|
LL | let x = 5 > 2 ? f32::MAX : f32::MIN;
| ^^^ the `?` operator cannot be applied to type `{integer}`
|
= help: the trait `Try` is not implemented for `{integer}`

error[E0277]: the `?` operator can only be used in a function that returns `Result` or `Option` (or another type that implements `FromResidual`)
--> $DIR/ternary_operator.rs:37:19
|
LL | fn c() {
| ------ this function should return `Result` or `Option` to accept `?`
LL | let x = 5 > 2 ? f32::MAX : f32::MIN;
| ^ cannot use the `?` operator in a function that returns `()`
|
= help: the trait `FromResidual<_>` is not implemented for `()`

error[E0277]: the `?` operator can only be applied to values that implement `Try`
--> $DIR/ternary_operator.rs:60:17
|
LL | let x = 5 > 2 ? { let x = vec![]: Vec<u16>; x } : { false };
| ^^^ the `?` operator cannot be applied to type `{integer}`
|
= help: the trait `Try` is not implemented for `{integer}`

error[E0277]: the `?` operator can only be used in a function that returns `Result` or `Option` (or another type that implements `FromResidual`)
--> $DIR/ternary_operator.rs:60:19
|
LL | fn main() {
| --------- this function should return `Result` or `Option` to accept `?`
LL | let x = 5 > 2 ? { let x = vec![]: Vec<u16>; x } : { false };
| ^ cannot use the `?` operator in a function that returns `()`
|
= help: the trait `FromResidual<_>` is not implemented for `()`

error: aborting due to 14 previous errors
error: aborting due to 6 previous errors

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

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