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Merged
merged 1 commit into from May 20, 2022
Merged

Improve u32 as char cast diagnostic #97169

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26 changes: 16 additions & 10 deletions compiler/rustc_typeck/src/check/cast.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -347,16 +347,22 @@ impl<'a, 'tcx> CastCheck<'tcx> {
);
err.span_label(self.span, "invalid cast");
if self.expr_ty.is_numeric() {
err.span_help(
self.span,
if self.expr_ty == fcx.tcx.types.i8 {
"try casting from `u8` instead"
} else if self.expr_ty == fcx.tcx.types.u32 {
"try `char::from_u32` instead"
} else {
"try `char::from_u32` instead (via a `u32`)"
},
);
if self.expr_ty == fcx.tcx.types.u32 {
match fcx.tcx.sess.source_map().span_to_snippet(self.expr.span) {
Ok(snippet) => err.span_suggestion(
self.span,
"try `char::from_u32` instead",
format!("char::from_u32({snippet})"),
Applicability::MachineApplicable,
),

Err(_) => err.span_help(self.span, "try `char::from_u32` instead"),
};
} else if self.expr_ty == fcx.tcx.types.i8 {
err.span_help(self.span, "try casting from `u8` instead");
} else {
err.span_help(self.span, "try `char::from_u32` instead (via a `u32`)");
};
}
err.emit();
}
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9 changes: 3 additions & 6 deletions src/test/ui/error-codes/E0604.stderr
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Original file line number Diff line number Diff line change
@@ -1,14 +1,11 @@
error[E0604]: only `u8` can be cast as `char`, not `u32`
--> $DIR/E0604.rs:2:5
|
LL | 1u32 as char;
| ^^^^^^^^^^^^ invalid cast
|
help: try `char::from_u32` instead
--> $DIR/E0604.rs:2:5
|
LL | 1u32 as char;
| ^^^^^^^^^^^^
| |
| invalid cast
| help: try `char::from_u32` instead: `char::from_u32(1u32)`

error: aborting due to previous error

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9 changes: 3 additions & 6 deletions src/test/ui/error-festival.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -56,14 +56,11 @@ LL | | }
error[E0604]: only `u8` can be cast as `char`, not `u32`
--> $DIR/error-festival.rs:25:5
|
LL | 0u32 as char;
| ^^^^^^^^^^^^ invalid cast
|
help: try `char::from_u32` instead
--> $DIR/error-festival.rs:25:5
|
LL | 0u32 as char;
| ^^^^^^^^^^^^
| |
| invalid cast
| help: try `char::from_u32` instead: `char::from_u32(0u32)`

error[E0605]: non-primitive cast: `u8` as `Vec<u8>`
--> $DIR/error-festival.rs:29:5
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9 changes: 3 additions & 6 deletions src/test/ui/mismatched_types/cast-rfc0401.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -97,14 +97,11 @@ LL | let _ = E::A as bool;
error[E0604]: only `u8` can be cast as `char`, not `u32`
--> $DIR/cast-rfc0401.rs:41:13
|
LL | let _ = 0x61u32 as char;
| ^^^^^^^^^^^^^^^ invalid cast
|
help: try `char::from_u32` instead
--> $DIR/cast-rfc0401.rs:41:13
|
LL | let _ = 0x61u32 as char;
| ^^^^^^^^^^^^^^^
| |
| invalid cast
| help: try `char::from_u32` instead: `char::from_u32(0x61u32)`

error[E0606]: casting `bool` as `f32` is invalid
--> $DIR/cast-rfc0401.rs:43:13
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