Auto merge of #86460 - JohnTitor:use-static-in-pattern-err, r=oli-obk

Refactor `PatternError` structure

Now we emit the `StaticInPattern` error precisely.
Fixes #68395
r? `@oli-obk`

Author: bors

compiler/rustc_mir_build/src/thir/pattern/mod.rs

@@ -423,6 +423,7 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
             _ => {
                 let pattern_error = match res {
                     Res::Def(DefKind::ConstParam, _) => PatternError::ConstParamInPattern(span),
+                    Res::Def(DefKind::Static, _) => PatternError::StaticInPattern(span),
                     _ => PatternError::NonConstPath(span),
                 };
                 self.errors.push(pattern_error);
@@ -468,11 +469,10 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
         let instance = match ty::Instance::resolve(self.tcx, param_env_reveal_all, def_id, substs) {
             Ok(Some(i)) => i,
             Ok(None) => {
-                self.errors.push(if is_associated_const {
-                    PatternError::AssocConstInPattern(span)
-                } else {
-                    PatternError::StaticInPattern(span)
-                });
+                // It should be assoc consts if there's no error but we cannot resolve it.
+                debug_assert!(is_associated_const);
+
+                self.errors.push(PatternError::AssocConstInPattern(span));
 
                 return pat_from_kind(PatKind::Wild);
             }

src/test/ui/issues/issue-27895.rs

@@ -0,0 +1,18 @@
+// Checks if we emit `PatternError`s correctly.
+// This is also a regression test for #27895 and #68394.
+
+static FOO: u8 = 10;
+
+fn main() {
+    let x = 0;
+    let 0u8..=x = 0;
+    //~^ ERROR: runtime values cannot be referenced in patterns
+    let 0u8..=FOO = 0;
+    //~^ ERROR: statics cannot be referenced in patterns
+    match 1 {
+        0 ..= x => {}
+        //~^ ERROR: runtime values cannot be referenced in patterns
+        0 ..= FOO => {}
+        //~^ ERROR: statics cannot be referenced in patterns
+    };
+}

src/test/ui/issues/issue-27895.stderr

@@ -0,0 +1,28 @@
+error[E0080]: runtime values cannot be referenced in patterns
+  --> $DIR/non-constant-in-const-path.rs:8:15
+   |
+LL |     let 0u8..=x = 0;
+   |               ^
+
+error[E0158]: statics cannot be referenced in patterns
+  --> $DIR/non-constant-in-const-path.rs:10:15
+   |
+LL |     let 0u8..=FOO = 0;
+   |               ^^^
+
+error[E0080]: runtime values cannot be referenced in patterns
+  --> $DIR/non-constant-in-const-path.rs:13:15
+   |
+LL |         0 ..= x => {}
+   |               ^
+
+error[E0158]: statics cannot be referenced in patterns
+  --> $DIR/non-constant-in-const-path.rs:15:15
+   |
+LL |         0 ..= FOO => {}
+   |               ^^^
+
+error: aborting due to 4 previous errors
+
+Some errors have detailed explanations: E0080, E0158.
+For more information about an error, try `rustc --explain E0080`.