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More accurately report error when formal and expected signature types differ

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This commit is contained in:
Michael Goulet 2022-11-10 20:20:25 +00:00
parent 312d6b8e9a
commit 55f1f993ff
3 changed files with 73 additions and 11 deletions
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29
compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
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@ -597,6 +597,18 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
}
};
let mk_trace = |span, (formal_ty, expected_ty), provided_ty| {
let mismatched_ty = if expected_ty == provided_ty {
// If expected == provided, then we must have failed to sup
// the formal type. Avoid printing out "expected Ty, found Ty"
// in that case.
formal_ty
} else {
expected_ty
};
TypeTrace::types(&self.misc(span), true, mismatched_ty, provided_ty)
};
// The algorithm here is inspired by levenshtein distance and longest common subsequence.
// We'll try to detect 4 different types of mistakes:
// - An extra parameter has been provided that doesn't satisfy *any* of the other inputs
@ -661,10 +673,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
// A tuple wrap suggestion actually occurs within,
// so don't do anything special here.
err = self.err_ctxt().report_and_explain_type_error(
TypeTrace::types(
&self.misc(*lo),
true,
formal_and_expected_inputs[mismatch_idx.into()].1,
mk_trace(
*lo,
formal_and_expected_inputs[mismatch_idx.into()],
provided_arg_tys[mismatch_idx.into()].0,
),
terr,
@ -748,9 +759,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
errors.drain_filter(|error| {
let Error::Invalid(provided_idx, expected_idx, Compatibility::Incompatible(Some(e))) = error else { return false };
let (provided_ty, provided_span) = provided_arg_tys[*provided_idx];
let (expected_ty, _) = formal_and_expected_inputs[*expected_idx];
let cause = &self.misc(provided_span);
let trace = TypeTrace::types(cause, true, expected_ty, provided_ty);
let trace = mk_trace(provided_span, formal_and_expected_inputs[*expected_idx], provided_ty);
if !matches!(trace.cause.as_failure_code(*e), FailureCode::Error0308(_)) {
self.err_ctxt().report_and_explain_type_error(trace, *e).emit();
return true;
@ -774,8 +783,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
{
let (formal_ty, expected_ty) = formal_and_expected_inputs[*expected_idx];
let (provided_ty, provided_arg_span) = provided_arg_tys[*provided_idx];
let cause = &self.misc(provided_arg_span);
let trace = TypeTrace::types(cause, true, expected_ty, provided_ty);
let trace = mk_trace(provided_arg_span, (formal_ty, expected_ty), provided_ty);
let mut err = self.err_ctxt().report_and_explain_type_error(trace, *err);
self.emit_coerce_suggestions(
&mut err,
@ -847,8 +855,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
let (formal_ty, expected_ty) = formal_and_expected_inputs[expected_idx];
let (provided_ty, provided_span) = provided_arg_tys[provided_idx];
if let Compatibility::Incompatible(error) = compatibility {
let cause = &self.misc(provided_span);
let trace = TypeTrace::types(cause, true, expected_ty, provided_ty);
let trace = mk_trace(provided_span, (formal_ty, expected_ty), provided_ty);
if let Some(e) = error {
self.err_ctxt().note_type_err(
&mut err,