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Improve error message for incorrect field accesses through raw pointers

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This commit is contained in:
Fabian Wolff 2021-11-29 19:31:17 +01:00
parent 5fd3a5c7c1
commit 821b92b102
4 changed files with 72 additions and 1 deletions
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32
compiler/rustc_typeck/src/check/expr.rs
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@ -46,6 +46,7 @@ use rustc_span::hygiene::DesugaringKind;
use rustc_span::lev_distance::find_best_match_for_name;
use rustc_span::source_map::Span;
use rustc_span::symbol::{kw, sym, Ident, Symbol};
use rustc_span::{BytePos, Pos};
use rustc_trait_selection::traits::{self, ObligationCauseCode};
impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
@ -2063,7 +2064,36 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
Some(span),
);
} else {
err.help("methods are immutable and cannot be assigned to");
let mut found = false;
if let ty::RawPtr(ty_and_mut) = expr_t.kind() {
if let ty::Adt(adt_def, _) = ty_and_mut.ty.kind() {
if adt_def.variants.len() == 1
&& adt_def
.variants
.iter()
.next()
.unwrap()
.fields
.iter()
.any(|f| f.ident == field)
{
if let Some(dot_loc) = expr_snippet.rfind('.') {
found = true;
err.span_suggestion(
expr.span.with_hi(expr.span.lo() + BytePos::from_usize(dot_loc)),
"to access the field, dereference first",
format!("(*{})", &expr_snippet[0..dot_loc]),
Applicability::MaybeIncorrect,
);
}
}
}
}
if !found {
err.help("methods are immutable and cannot be assigned to");
}
}
err.emit();