rustc_error: make ErrorReported impossible to construct

There are a few places were we have to construct it, though, and a few
places that are more invasive to change. To do this, we create a
constructor with a long obvious name.

compiler/rustc_ast_passes/src/ast_validation.rs

@@ -440,7 +440,7 @@ impl<'a> AstValidator<'a> {
                         attr.span,
                         "allow, cfg, cfg_attr, deny, \
                 forbid, and warn are the only allowed built-in attributes in function parameters",
-                    )
+                    );
                 }
             });
     }

compiler/rustc_ast_passes/src/feature_gate.rs

@@ -252,11 +252,12 @@ impl<'a> PostExpansionVisitor<'a> {
                     "wasm ABI is experimental and subject to change"
                 );
             }
-            abi => self
-                .sess
-                .parse_sess
-                .span_diagnostic
-                .delay_span_bug(span, &format!("unrecognized ABI not caught in lowering: {}", abi)),
+            abi => {
+                self.sess.parse_sess.span_diagnostic.delay_span_bug(
+                    span,
+                    &format!("unrecognized ABI not caught in lowering: {}", abi),
+                );
+            }
         }
     }