Keep Disallowing return in ambient locations

Author: sandersn

src/compiler/checker.ts

@@ -38913,7 +38913,7 @@ namespace ts {
             }
 
             if (!container) {
-                if (!!getSourceFileOfNode(node).externalModuleIndicator) {
+                if (!!getSourceFileOfNode(node).externalModuleIndicator || node.flags & NodeFlags.Ambient) {
                     grammarErrorOnFirstToken(node, Diagnostics.A_return_statement_can_only_be_used_within_a_function_body);
                 }
                 return;

tests/baselines/reference/ambientWithStatements.errors.txt

@@ -1,9 +1,10 @@
 tests/cases/compiler/ambientWithStatements.ts(2,5): error TS1036: Statements are not allowed in ambient contexts.
 tests/cases/compiler/ambientWithStatements.ts(3,5): error TS1104: A 'continue' statement can only be used within an enclosing iteration statement.
+tests/cases/compiler/ambientWithStatements.ts(11,5): error TS1108: A 'return' statement can only be used within a function body.
 tests/cases/compiler/ambientWithStatements.ts(25,5): error TS2410: The 'with' statement is not supported. All symbols in a 'with' block will have type 'any'.
 
 
-==== tests/cases/compiler/ambientWithStatements.ts (3 errors) ====
+==== tests/cases/compiler/ambientWithStatements.ts (4 errors) ====
     declare module M {
         break;
         ~~~~~
@@ -19,6 +20,8 @@ tests/cases/compiler/ambientWithStatements.ts(25,5): error TS2410: The 'with' st
         1;
         L: var y;
         return;
+        ~~~~~~
+!!! error TS1108: A 'return' statement can only be used within a function body.
         switch (x) {
             case 1:
                 break;