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Auto merge of #95104 - compiler-errors:remove-ascription, r=davidtwco
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suggest removing type ascription in bad parsing position

Not sure how to test this with the non-nightly suggestion. Didn't add a new UI test because it already manifests in an existing UI test.

Fixes #95014
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@bors
bors committed Mar 21, 2022
2 parents eded76b + 3516a16 commit 051d117
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Showing 2 changed files with 115 additions and 6 deletions.
41 changes: 35 additions & 6 deletions compiler/rustc_parse/src/parser/expr.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -800,11 +800,17 @@ impl<'a> Parser<'a> {
&mut self,
cast_expr: P<Expr>,
) -> PResult<'a, P<Expr>> {
let span = cast_expr.span;
let maybe_ascription_span = if let ExprKind::Type(ascripted_expr, _) = &cast_expr.kind {
Some(ascripted_expr.span.shrink_to_hi().with_hi(span.hi()))
} else {
None
};

// Save the memory location of expr before parsing any following postfix operators.
// This will be compared with the memory location of the output expression.
// If they different we can assume we parsed another expression because the existing expression is not reallocated.
let addr_before = &*cast_expr as *const _ as usize;
let span = cast_expr.span;
let with_postfix = self.parse_dot_or_call_expr_with_(cast_expr, span)?;
let changed = addr_before != &*with_postfix as *const _ as usize;

Expand All @@ -825,11 +831,8 @@ impl<'a> Parser<'a> {
}
);
let mut err = self.struct_span_err(span, &msg);
// If type ascription is "likely an error", the user will already be getting a useful
// help message, and doesn't need a second.
if self.last_type_ascription.map_or(false, |last_ascription| last_ascription.1) {
self.maybe_annotate_with_ascription(&mut err, false);
} else {

let suggest_parens = |err: &mut DiagnosticBuilder<'_, _>| {
let suggestions = vec![
(span.shrink_to_lo(), "(".to_string()),
(span.shrink_to_hi(), ")".to_string()),
Expand All @@ -839,6 +842,32 @@ impl<'a> Parser<'a> {
suggestions,
Applicability::MachineApplicable,
);
};

// If type ascription is "likely an error", the user will already be getting a useful
// help message, and doesn't need a second.
if self.last_type_ascription.map_or(false, |last_ascription| last_ascription.1) {
self.maybe_annotate_with_ascription(&mut err, false);
} else if let Some(ascription_span) = maybe_ascription_span {
let is_nightly = self.sess.unstable_features.is_nightly_build();
if is_nightly {
suggest_parens(&mut err);
}
err.span_suggestion(
ascription_span,
&format!(
"{}remove the type ascription",
if is_nightly { "alternatively, " } else { "" }
),
String::new(),
if is_nightly {
Applicability::MaybeIncorrect
} else {
Applicability::MachineApplicable
},
);
} else {
suggest_parens(&mut err);
}
err.emit();
};
Expand Down
80 changes: 80 additions & 0 deletions src/test/ui/parser/issues/issue-35813-postfix-after-cast.stderr
View file
Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,11 @@ help: try surrounding the expression in parentheses
|
LL | (vec![1, 2, 3]: Vec<i32>)[0];
| + +
help: alternatively, remove the type ascription
|
LL - vec![1, 2, 3]: Vec<i32>[0];
LL + vec![1, 2, 3][0];
|

error: casts cannot be followed by indexing
--> $DIR/issue-35813-postfix-after-cast.rs:17:5
Expand All @@ -41,6 +46,11 @@ help: try surrounding the expression in parentheses
|
LL | ((&[0i32]): &[i32; 1])[0];
| + +
help: alternatively, remove the type ascription
|
LL - (&[0i32]): &[i32; 1][0];
LL + (&[0i32])[0];
|

error: casts cannot be followed by a method call
--> $DIR/issue-35813-postfix-after-cast.rs:39:13
Expand All @@ -52,6 +62,11 @@ help: try surrounding the expression in parentheses
|
LL | let _ = (0i32: i32: i32).count_ones();
| + +
help: alternatively, remove the type ascription
|
LL - let _ = 0i32: i32: i32.count_ones();
LL + let _ = 0i32: i32.count_ones();
|

error: casts cannot be followed by a method call
--> $DIR/issue-35813-postfix-after-cast.rs:41:13
Expand All @@ -63,6 +78,11 @@ help: try surrounding the expression in parentheses
|
LL | let _ = (0 as i32: i32).count_ones();
| + +
help: alternatively, remove the type ascription
|
LL - let _ = 0 as i32: i32.count_ones();
LL + let _ = 0 as i32.count_ones();
|

error: casts cannot be followed by a method call
--> $DIR/issue-35813-postfix-after-cast.rs:43:13
Expand Down Expand Up @@ -107,6 +127,11 @@ help: try surrounding the expression in parentheses
|
LL | let _ = (0i32: i32).count_ones(): u32;
| + +
help: alternatively, remove the type ascription
|
LL - let _ = 0i32: i32.count_ones(): u32;
LL + let _ = 0i32.count_ones(): u32;
|

error: casts cannot be followed by a method call
--> $DIR/issue-35813-postfix-after-cast.rs:51:13
Expand All @@ -129,6 +154,11 @@ help: try surrounding the expression in parentheses
|
LL | let _ = (0i32: i32).count_ones() as u32;
| + +
help: alternatively, remove the type ascription
|
LL - let _ = 0i32: i32.count_ones() as u32;
LL + let _ = 0i32.count_ones() as u32;
|

error: casts cannot be followed by a method call
--> $DIR/issue-35813-postfix-after-cast.rs:55:13
Expand All @@ -151,6 +181,11 @@ help: try surrounding the expression in parentheses
|
LL | let _ = (0i32: i32: i32).count_ones() as u32 as i32;
| + +
help: alternatively, remove the type ascription
|
LL - let _ = 0i32: i32: i32.count_ones() as u32 as i32;
LL + let _ = 0i32: i32.count_ones() as u32 as i32;
|

error: casts cannot be followed by a method call
--> $DIR/issue-35813-postfix-after-cast.rs:62:13
Expand Down Expand Up @@ -198,6 +233,11 @@ help: try surrounding the expression in parentheses
|
LL | (0: i32).max(0);
| + +
help: alternatively, remove the type ascription
|
LL - 0: i32.max(0);
LL + 0.max(0);
|

error: casts cannot be followed by a method call
--> $DIR/issue-35813-postfix-after-cast.rs:92:8
Expand All @@ -220,6 +260,11 @@ help: try surrounding the expression in parentheses
|
LL | if (5u64: u64).max(0) == 0 {
| + +
help: alternatively, remove the type ascription
|
LL - if 5u64: u64.max(0) == 0 {
LL + if 5u64.max(0) == 0 {
|

error: casts cannot be followed by a method call
--> $DIR/issue-35813-postfix-after-cast.rs:102:9
Expand All @@ -242,6 +287,11 @@ help: try surrounding the expression in parentheses
|
LL | (5u64: u64).max(0) == 0
| + +
help: alternatively, remove the type ascription
|
LL - 5u64: u64.max(0) == 0
LL + 5u64.max(0) == 0
|

error: casts cannot be followed by indexing
--> $DIR/issue-35813-postfix-after-cast.rs:111:24
Expand All @@ -264,6 +314,11 @@ help: try surrounding the expression in parentheses
|
LL | static bar2: &[i32] = &((&[1i32,2,3]: &[i32; 3])[0..1]);
| + +
help: alternatively, remove the type ascription
|
LL - static bar2: &[i32] = &(&[1i32,2,3]: &[i32; 3][0..1]);
LL + static bar2: &[i32] = &(&[1i32,2,3][0..1]);
|

error: casts cannot be followed by `?`
--> $DIR/issue-35813-postfix-after-cast.rs:119:5
Expand All @@ -286,6 +341,11 @@ help: try surrounding the expression in parentheses
|
LL | (Err(0u64): Result<u64,u64>)?;
| + +
help: alternatively, remove the type ascription
|
LL - Err(0u64): Result<u64,u64>?;
LL + Err(0u64)?;
|

error: casts cannot be followed by a function call
--> $DIR/issue-35813-postfix-after-cast.rs:145:5
Expand All @@ -308,6 +368,11 @@ help: try surrounding the expression in parentheses
|
LL | (drop_ptr: fn(u8))(0);
| + +
help: alternatively, remove the type ascription
|
LL - drop_ptr: fn(u8)(0);
LL + drop_ptr(0);
|

error: casts cannot be followed by `.await`
--> $DIR/issue-35813-postfix-after-cast.rs:152:5
Expand All @@ -330,6 +395,11 @@ help: try surrounding the expression in parentheses
|
LL | (Box::pin(noop()): Pin<Box<_>>).await;
| + +
help: alternatively, remove the type ascription
|
LL - Box::pin(noop()): Pin<Box<_>>.await;
LL + Box::pin(noop()).await;
|

error: casts cannot be followed by a field access
--> $DIR/issue-35813-postfix-after-cast.rs:167:5
Expand All @@ -352,6 +422,11 @@ help: try surrounding the expression in parentheses
|
LL | (Foo::default(): Foo).bar;
| + +
help: alternatively, remove the type ascription
|
LL - Foo::default(): Foo.bar;
LL + Foo::default().bar;
|

error: casts cannot be followed by a method call
--> $DIR/issue-35813-postfix-after-cast.rs:84:9
Expand All @@ -374,6 +449,11 @@ help: try surrounding the expression in parentheses
|
LL | (if true { 33 } else { 44 }: i32).max(0)
| + +
help: alternatively, remove the type ascription
|
LL - if true { 33 } else { 44 }: i32.max(0)
LL + if true { 33 } else { 44 }.max(0)
|

error[E0214]: parenthesized type parameters may only be used with a `Fn` trait
--> $DIR/issue-35813-postfix-after-cast.rs:131:13
Expand Down

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