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Auto merge of #114397 - sebastiantoh:issue-85222, r=Nadrieril

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Add note when matching on tuples/ADTs containing non-exhaustive types

Fixes https://github.com/rust-lang/rust/issues/85222

r? `@Nadrieril`
This commit is contained in:
bors 2023-08-25 01:44:07 +00:00
commit c75b6bdb37
6 changed files with 276 additions and 14 deletions
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45
compiler/rustc_mir_build/src/thir/pattern/check_match.rs
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@ -7,6 +7,7 @@ use crate::errors::*;
use rustc_arena::TypedArena;
use rustc_ast::Mutability;
use rustc_data_structures::fx::FxHashSet;
use rustc_data_structures::stack::ensure_sufficient_stack;
use rustc_errors::{
struct_span_err, Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed, MultiSpan,
@ -660,6 +661,17 @@ fn report_arm_reachability<'p, 'tcx>(
}
}
fn collect_non_exhaustive_tys<'p, 'tcx>(
pat: &DeconstructedPat<'p, 'tcx>,
non_exhaustive_tys: &mut FxHashSet<Ty<'tcx>>,
) {
if matches!(pat.ctor(), Constructor::NonExhaustive) {
non_exhaustive_tys.insert(pat.ty());
}
pat.iter_fields()
.for_each(|field_pat| collect_non_exhaustive_tys(field_pat, non_exhaustive_tys))
}
/// Report that a match is not exhaustive.
fn non_exhaustive_match<'p, 'tcx>(
cx: &MatchCheckCtxt<'p, 'tcx>,
@ -717,22 +729,27 @@ fn non_exhaustive_match<'p, 'tcx>(
scrut_ty,
if is_variant_list_non_exhaustive { ", which is marked as non-exhaustive" } else { "" }
));
if (scrut_ty == cx.tcx.types.usize || scrut_ty == cx.tcx.types.isize)
&& !is_empty_match
&& witnesses.len() == 1
&& matches!(witnesses[0].ctor(), Constructor::NonExhaustive)
{
err.note(format!(
"`{scrut_ty}` does not have a fixed maximum value, so a wildcard `_` is necessary to match \
exhaustively",
));
if cx.tcx.sess.is_nightly_build() {
err.help(format!(
"add `#![feature(precise_pointer_size_matching)]` to the crate attributes to \
enable precise `{scrut_ty}` matching",
));
if !is_empty_match && witnesses.len() == 1 {
let mut non_exhaustive_tys = FxHashSet::default();
collect_non_exhaustive_tys(&witnesses[0], &mut non_exhaustive_tys);
for ty in non_exhaustive_tys {
if ty == cx.tcx.types.usize || ty == cx.tcx.types.isize {
err.note(format!(
"`{ty}` does not have a fixed maximum value, so a wildcard `_` is necessary to match \
exhaustively",
));
if cx.tcx.sess.is_nightly_build() {
err.help(format!(
"add `#![feature(precise_pointer_size_matching)]` to the crate attributes to \
enable precise `{ty}` matching",
));
}
}
}
}
if let ty::Ref(_, sub_ty, _) = scrut_ty.kind() {
if !sub_ty.is_inhabited_from(cx.tcx, cx.module, cx.param_env) {
err.note("references are always considered inhabited");