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Show discriminant before overflow in diagnostic.

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This commit is contained in:
Maarten de Vries 2021-07-15 21:25:11 +02:00
parent 8b50cc9a2c
commit 4c0ff4db80
5 changed files with 52 additions and 8 deletions
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27
compiler/rustc_typeck/src/check/check.rs
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@ -1472,15 +1472,17 @@ fn check_enum<'tcx>(
Some(ref expr) => tcx.hir().span(expr.hir_id),
None => v.span,
};
let display_discr = display_discriminant_value(tcx, v, discr.val);
let display_discr_i = display_discriminant_value(tcx, variant_i, disr_vals[i].val);
struct_span_err!(
tcx.sess,
span,
E0081,
"discriminant value `{}` already exists",
disr_vals[i]
discr.val,
)
.span_label(i_span, format!("first use of `{}`", disr_vals[i]))
.span_label(span, format!("enum already has `{}`", disr_vals[i]))
.span_label(i_span, format!("first use of {}", display_discr_i))
.span_label(span, format!("enum already has {}", display_discr))
.emit();
}
disr_vals.push(discr);
@ -1490,6 +1492,25 @@ fn check_enum<'tcx>(
check_transparent(tcx, sp, def);
}
/// Format an enum discriminant value for use in a diagnostic message.
fn display_discriminant_value<'tcx>(
tcx: TyCtxt<'tcx>,
variant: &hir::Variant<'_>,
evaluated: u128,
) -> String {
if let Some(expr) = &variant.disr_expr {
let body = &tcx.hir().body(expr.body).value;
if let hir::ExprKind::Lit(lit) = &body.kind {
if let rustc_ast::LitKind::Int(lit_value, _int_kind) = &lit.node {
if evaluated != *lit_value {
return format!("`{}` (overflowed from `{}`)", evaluated, lit_value);
}
}
}
}
format!("`{}`", evaluated)
}
pub(super) fn check_type_params_are_used<'tcx>(
tcx: TyCtxt<'tcx>,
generics: &ty::Generics,