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make CastError::NeedsDeref create a MachineApplicable suggestion #106927

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Merged
merged 2 commits into from
Jan 19, 2023
Merged

make CastError::NeedsDeref create a MachineApplicable suggestion #106927

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ca1178f
make `CastError::NeedsDeref` create a `MachineApplicable` suggestion …
Ezrashaw Jan 16, 2023
b73cdf1
special case removing `&` suggestion
Ezrashaw Jan 18, 2023
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30 changes: 11 additions & 19 deletions compiler/rustc_hir_typeck/src/cast.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -151,7 +151,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {

#[derive(Copy, Clone)]
pub enum CastError {
ErrorGuaranteed,
ErrorGuaranteed(ErrorGuaranteed),

CastToBool,
CastToChar,
Expand All @@ -176,8 +176,8 @@ pub enum CastError {
}

impl From<ErrorGuaranteed> for CastError {
fn from(_: ErrorGuaranteed) -> Self {
CastError::ErrorGuaranteed
fn from(err: ErrorGuaranteed) -> Self {
CastError::ErrorGuaranteed(err)
}
}

Expand Down Expand Up @@ -225,33 +225,25 @@ impl<'a, 'tcx> CastCheck<'tcx> {

fn report_cast_error(&self, fcx: &FnCtxt<'a, 'tcx>, e: CastError) {
match e {
CastError::ErrorGuaranteed => {
CastError::ErrorGuaranteed(_) => {
// an error has already been reported
}
CastError::NeedDeref => {
let error_span = self.span;
let mut err = make_invalid_casting_error(
fcx.tcx.sess,
self.span,
self.expr_ty,
self.cast_ty,
fcx,
);
let cast_ty = fcx.ty_to_string(self.cast_ty);
err.span_label(
error_span,
format!("cannot cast `{}` as `{}`", fcx.ty_to_string(self.expr_ty), cast_ty),

err.span_suggestion_verbose(
self.expr_span.shrink_to_lo(),
"dereference the expression",
"*",
Applicability::MachineApplicable,
);
if let Ok(snippet) = fcx.sess().source_map().span_to_snippet(self.expr_span) {
err.span_suggestion(
self.expr_span,
"dereference the expression",
format!("*{}", snippet),
Applicability::MaybeIncorrect,
);
} else {
err.span_help(self.expr_span, "dereference the expression with `*`");
}

err.emit();
}
CastError::NeedViaThinPtr | CastError::NeedViaPtr => {
Expand Down
10 changes: 6 additions & 4 deletions tests/ui/error-codes/E0606.stderr
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Expand Up @@ -2,10 +2,12 @@ error[E0606]: casting `&u8` as `u8` is invalid
--> $DIR/E0606.rs:2:5
|
LL | &0u8 as u8;
| ----^^^^^^
| |
| cannot cast `&u8` as `u8`
| help: dereference the expression: `*&0u8`
| ^^^^^^^^^^
|
help: dereference the expression
|
LL | *&0u8 as u8;
| +
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You have access to the expression through self.expr. Would you mind special casing hir::ExprKind::AddrOf to suggest removing the & instead?


error: aborting due to previous error

Expand Down
10 changes: 6 additions & 4 deletions tests/ui/error-festival.stderr
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Expand Up @@ -69,10 +69,12 @@ error[E0606]: casting `&u8` as `u32` is invalid
--> $DIR/error-festival.rs:37:18
|
LL | let y: u32 = x as u32;
| -^^^^^^^
| |
| cannot cast `&u8` as `u32`
| help: dereference the expression: `*x`
| ^^^^^^^^
|
help: dereference the expression
|
LL | let y: u32 = *x as u32;
| +

error[E0607]: cannot cast thin pointer `*const u8` to fat pointer `*const [u8]`
--> $DIR/error-festival.rs:41:5
Expand Down
10 changes: 6 additions & 4 deletions tests/ui/mismatched_types/cast-rfc0401.stderr
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Expand Up @@ -243,10 +243,12 @@ error[E0606]: casting `&{float}` as `f32` is invalid
--> $DIR/cast-rfc0401.rs:71:30
|
LL | vec![0.0].iter().map(|s| s as f32).collect::<Vec<f32>>();
| -^^^^^^^
| |
| cannot cast `&{float}` as `f32`
| help: dereference the expression: `*s`
| ^^^^^^^^
|
help: dereference the expression
|
LL | vec![0.0].iter().map(|s| *s as f32).collect::<Vec<f32>>();
| +

error: aborting due to 34 previous errors

Expand Down