Sema: Reject invalid attributes on local variables in result builders

Fixes <rdar://problem/73545981>.

Author: slavapestov

lib/Sema/BuilderTransform.cpp

@@ -288,6 +288,9 @@ class BuilderClosureVisitor
             unhandledNode = patternBinding;
           return;
         }
+
+        // Also check for invalid attributes.
+        TypeChecker::checkDeclAttributes(var);
       }
     }
 

test/Constraints/result_builder_invalid_vars.swift

@@ -43,3 +43,9 @@ dummy {
   @Wrapper var wrappedVar: Int = 123 // expected-error {{closure containing a declaration cannot be used with result builder 'DummyBuilder'}}
   ()
 }
+
+dummy {
+  @resultBuilder var attributedVar: Int = 123 // expected-error {{@resultBuilder' attribute cannot be applied to this declaration}}
+  // expected-warning@-1 {{variable 'attributedVar' was never used; consider replacing with '_' or removing it}}
+  ()
+}