fix: Skip export default in namespace (#2267)

Author: technohippy

Diff for: src/diagnosticMessages.json

@@ -115,6 +115,7 @@
   "A definite assignment assertion '!' is not permitted in this context.": 1255,
   "A class may only extend another class.": 1311,
   "A parameter property cannot be declared using a rest parameter.": 1317,
+  "A default export can only be used in a module.": 1319,
   "An identifier or keyword cannot immediately follow a numeric literal.": 1351,
 
   "Duplicate identifier '{0}'.": 2300,

Diff for: src/parser.ts

@@ -2506,8 +2506,16 @@ export class Parser extends DiagnosticEmitter {
         );
         while (!tn.skip(Token.CLOSEBRACE)) {
           let member = this.parseTopLevelStatement(tn, declaration);
-          if (member) members.push(member);
-          else {
+          if (member) {
+            if (member.kind == NodeKind.EXPORT) {
+              this.error(
+                DiagnosticCode.A_default_export_can_only_be_used_in_a_module,
+                member.range,
+              );
+              return null;
+            }
+            members.push(member);
+          } else {
             this.skipStatement(tn);
             if (tn.skip(Token.ENDOFFILE)) {
               this.error(

Diff for: tests/parser/export-default-in-namespace.ts

@@ -0,0 +1,3 @@
+namespace Foo {
+  export default bar;
+}

Diff for: tests/parser/export-default-in-namespace.ts.fixture.ts

@@ -0,0 +1 @@
+// ERROR 1319: "A default export can only be used in a module." in export-default-in-namespace.ts(2,3+18)