Auto merge of #108504 - cjgillot:thir-pattern, r=compiler-errors,Nilstrieb

Check pattern refutability on THIR

The current `check_match` query is based on HIR, but partially re-lowers HIR into THIR.
This PR proposed to use the results of the `thir_body` query to check matches, instead of re-building THIR.

Most of the diagnostic changes are spans getting shorter, or commas/semicolons not getting removed.

This PR degrades the diagnostic for confusing constants in patterns (`let A = foo()` where `A` resolves to a `const A` somewhere): it does not point ot the definition of `const A` any more.

Author: bors

compiler/rustc_hir/src/pat_util.rs

@@ -2,7 +2,6 @@ use crate::def::{CtorOf, DefKind, Res};
 use crate::def_id::DefId;
 use crate::hir::{self, BindingAnnotation, ByRef, HirId, PatKind};
 use rustc_data_structures::fx::FxHashSet;
-use rustc_span::hygiene::DesugaringKind;
 use rustc_span::symbol::Ident;
 use rustc_span::Span;
 
@@ -136,14 +135,4 @@ impl hir::Pat<'_> {
         });
         result
     }
-
-    /// If the pattern is `Some(<pat>)` from a desugared for loop, returns the inner pattern
-    pub fn for_loop_some(&self) -> Option<&Self> {
-        if self.span.desugaring_kind() == Some(DesugaringKind::ForLoop) {
-            if let hir::PatKind::Struct(_, [pat_field], _) = self.kind {
-                return Some(pat_field.pat);
-            }
-        }
-        None
-    }
 }

compiler/rustc_interface/src/passes.rs

@@ -765,7 +765,7 @@ fn analysis(tcx: TyCtxt<'_>, (): ()) -> Result<()> {
         parallel!(
             {
                 sess.time("match_checking", || {
-                    tcx.hir().par_body_owners(|def_id| tcx.ensure().check_match(def_id.to_def_id()))
+                    tcx.hir().par_body_owners(|def_id| tcx.ensure().check_match(def_id))
                 });
             },
             {