loop match: handle opaque patterns

fixes issue 143203

compiler/rustc_mir_build/src/builder/matches/mod.rs

@@ -2970,6 +2970,9 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             }
             Constructor::Wildcard => true,
 
+            // Opaque patterns must not be matched on structurally.
+            Constructor::Opaque(_) => false,
+
             // These we may eventually support:
             Constructor::Struct
             | Constructor::Ref
@@ -2980,8 +2983,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             | Constructor::Str(_) => bug!("unsupported pattern constructor {:?}", pat.ctor()),
 
             // These should never occur here:
-            Constructor::Opaque(_)
-            | Constructor::Never
+            Constructor::Never
             | Constructor::NonExhaustive
             | Constructor::Hidden
             | Constructor::Missing

compiler/rustc_mir_build/src/errors.rs

@@ -1230,7 +1230,6 @@ pub(crate) struct ConstContinueMissingValue {
 
 #[derive(Diagnostic)]
 #[diag(mir_build_const_continue_unknown_jump_target)]
-#[note]
 pub(crate) struct ConstContinueUnknownJumpTarget {
     #[primary_span]
     pub span: Span,

tests/ui/loop-match/invalid.rs

@@ -172,3 +172,21 @@ fn non_exhaustive() {
         }
     }
 }
+
+fn invalid_range_pattern(state: f32) {
+    #[loop_match]
+    loop {
+        state = 'blk: {
+            match state {
+                1.0 => {
+                    #[const_continue]
+                    break 'blk 2.5;
+                }
+                4.0..3.0 => {
+                    //~^ ERROR lower range bound must be less than upper
+                    todo!()
+                }
+            }
+        }
+    }
+}

tests/ui/loop-match/invalid.stderr

@@ -109,7 +109,13 @@ LL ~                 State::A => State::B,
 LL ~                 State::B | State::C => todo!(),
    |
 
-error: aborting due to 13 previous errors
+error[E0579]: lower range bound must be less than upper
+  --> $DIR/invalid.rs:185:17
+   |
+LL |                 4.0..3.0 => {
+   |                 ^^^^^^^^
 
-Some errors have detailed explanations: E0004, E0308.
+error: aborting due to 14 previous errors
+
+Some errors have detailed explanations: E0004, E0308, E0579.
 For more information about an error, try `rustc --explain E0004`.