Prevent ICE for doc_alias on match arm, statement, expression

Author: hdelc

compiler/rustc_passes/src/check_attr.rs

@@ -619,6 +619,9 @@ impl CheckAttrVisitor<'_> {
             }
             // we check the validity of params elsewhere
             Target::Param => return false,
+            Target::Expression => Some("expression"),
+            Target::Statement => Some("statement"),
+            Target::Arm => Some("match arm"),
             _ => None,
         } {
             tcx.sess.emit_err(errors::DocAliasBadLocation { span, attr_str, location });

src/test/ui/rustdoc/check-doc-alias-attr-location.rs

@@ -21,6 +21,12 @@ impl Foo for Bar {
     type X = i32;
     fn foo(#[doc(alias = "qux")] _x: u32) -> Self::X {
         //~^ ERROR
-        0
+        #[doc(alias = "stmt")] //~ ERROR
+        let x = 0;
+        #[doc(alias = "expr")] //~ ERROR
+        match x {
+            #[doc(alias = "arm")] //~ ERROR
+            _ => 0
+        }
     }
 }

src/test/ui/rustdoc/check-doc-alias-attr-location.stderr

@@ -28,5 +28,23 @@ error: `#[doc(alias = "...")]` isn't allowed on type alias in implementation blo
 LL |     #[doc(alias = "assoc")]
    |           ^^^^^^^^^^^^^^^
 
-error: aborting due to 5 previous errors
+error: `#[doc(alias = "...")]` isn't allowed on statement
+  --> $DIR/check-doc-alias-attr-location.rs:24:15
+   |
+LL |         #[doc(alias = "stmt")]
+   |               ^^^^^^^^^^^^^^
+
+error: `#[doc(alias = "...")]` isn't allowed on expression
+  --> $DIR/check-doc-alias-attr-location.rs:26:15
+   |
+LL |         #[doc(alias = "expr")]
+   |               ^^^^^^^^^^^^^^
+
+error: `#[doc(alias = "...")]` isn't allowed on match arm
+  --> $DIR/check-doc-alias-attr-location.rs:28:19
+   |
+LL |             #[doc(alias = "arm")]
+   |                   ^^^^^^^^^^^^^
+
+error: aborting due to 8 previous errors