Allow export default interface. Related to issue 3792.

src/compiler/parser.ts

@@ -1237,12 +1237,12 @@ namespace ts {
             if (token() === SyntaxKind.ExportKeyword) {
                 nextToken();
                 if (token() === SyntaxKind.DefaultKeyword) {
-                    return lookAhead(nextTokenIsClassOrFunctionOrAsync);
+                    return lookAhead(nextTokenCanFollowDefaultKeyword);
                 }
                 return token() !== SyntaxKind.AsteriskToken && token() !== SyntaxKind.AsKeyword && token() !== SyntaxKind.OpenBraceToken && canFollowModifier();
             }
             if (token() === SyntaxKind.DefaultKeyword) {
-                return nextTokenIsClassOrFunctionOrAsync();
+                return nextTokenCanFollowDefaultKeyword();
             }
             if (token() === SyntaxKind.StaticKeyword) {
                 nextToken();
@@ -1264,9 +1264,10 @@ namespace ts {
                 || isLiteralPropertyName();
         }
 
-        function nextTokenIsClassOrFunctionOrAsync(): boolean {
+        function nextTokenCanFollowDefaultKeyword(): boolean {
             nextToken();
             return token() === SyntaxKind.ClassKeyword || token() === SyntaxKind.FunctionKeyword ||
+                token() === SyntaxKind.InterfaceKeyword ||
                 (token() === SyntaxKind.AbstractKeyword && lookAhead(nextTokenIsClassKeywordOnSameLine)) ||
                 (token() === SyntaxKind.AsyncKeyword && lookAhead(nextTokenIsFunctionKeywordOnSameLine));
         }

tests/baselines/reference/exportDefaultInterface.js

@@ -0,0 +1,15 @@
+//// [tests/cases/compiler/exportDefaultInterface.ts] ////
+
+//// [a.ts]
+export default interface A {}
+
+//// [b.ts]
+import A from './a'
+
+
+//// [a.js]
+"use strict";
+exports.__esModule = true;
+//// [b.js]
+"use strict";
+exports.__esModule = true;

tests/baselines/reference/exportDefaultInterface.symbols

@@ -0,0 +1,8 @@
+=== tests/cases/compiler/a.ts ===
+export default interface A {}
+>A : Symbol(A, Decl(a.ts, 0, 0))
+
+=== tests/cases/compiler/b.ts ===
+import A from './a'
+>A : Symbol(A, Decl(b.ts, 0, 6))
+

tests/baselines/reference/exportDefaultInterface.types

@@ -0,0 +1,8 @@
+=== tests/cases/compiler/a.ts ===
+export default interface A {}
+>A : A
+
+=== tests/cases/compiler/b.ts ===
+import A from './a'
+>A : any
+

tests/cases/compiler/exportDefaultInterface.ts

@@ -0,0 +1,5 @@
+// @filename: a.ts
+export default interface A {}
+
+// @filename: b.ts
+import A from './a'