bjoernager/rust
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suggest removing type ascription in bad position

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This commit is contained in:
Michael Goulet 2022-03-18 20:45:15 -07:00
parent 1bfe40d11c
commit 3516a16eeb
2 changed files with 115 additions and 6 deletions
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41
compiler/rustc_parse/src/parser/expr.rs
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@ -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;
@ -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()),
@ -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();
};