Allow export default abstract class. Related to issue 3792.

Author: erikmcc

src/compiler/parser.ts

@@ -1267,6 +1267,7 @@ namespace ts {
         function nextTokenIsClassOrFunctionOrAsync(): boolean {
             nextToken();
             return token() === SyntaxKind.ClassKeyword || token() === SyntaxKind.FunctionKeyword ||
+                (token() === SyntaxKind.AbstractKeyword && lookAhead(nextTokenIsClassKeywordOnSameLine)) ||
                 (token() === SyntaxKind.AsyncKeyword && lookAhead(nextTokenIsFunctionKeywordOnSameLine));
         }
 
@@ -4658,6 +4659,11 @@ namespace ts {
             return tokenIsIdentifierOrKeyword(token()) && !scanner.hasPrecedingLineBreak();
         }
 
+        function nextTokenIsClassKeywordOnSameLine() {
+            nextToken();
+            return token() === SyntaxKind.ClassKeyword && !scanner.hasPrecedingLineBreak();
+        }
+
         function nextTokenIsFunctionKeywordOnSameLine() {
             nextToken();
             return token() === SyntaxKind.FunctionKeyword && !scanner.hasPrecedingLineBreak();

tests/baselines/reference/classAbstractManyKeywords.errors.txt

@@ -1,12 +1,9 @@
-tests/cases/conformance/classes/classDeclarations/classAbstractKeyword/classAbstractManyKeywords.ts(1,25): error TS1005: ';' expected.
 tests/cases/conformance/classes/classDeclarations/classAbstractKeyword/classAbstractManyKeywords.ts(3,1): error TS1128: Declaration or statement expected.
 tests/cases/conformance/classes/classDeclarations/classAbstractKeyword/classAbstractManyKeywords.ts(4,17): error TS1005: '=' expected.
 
 
-==== tests/cases/conformance/classes/classDeclarations/classAbstractKeyword/classAbstractManyKeywords.ts (3 errors) ====
+==== tests/cases/conformance/classes/classDeclarations/classAbstractKeyword/classAbstractManyKeywords.ts (2 errors) ====
     export default abstract class A {}
-                            ~~~~~
-!!! error TS1005: ';' expected.
     export abstract class B {}
     default abstract class C {}
     ~~~~~~~

tests/baselines/reference/classAbstractManyKeywords.js

@@ -7,12 +7,12 @@ import abstract class D {}
 //// [classAbstractManyKeywords.js]
 "use strict";
 exports.__esModule = true;
-exports["default"] = abstract;
 var A = (function () {
     function A() {
     }
     return A;
 }());
+exports["default"] = A;
 var B = (function () {
     function B() {
     }
@@ -24,7 +24,6 @@ var C = (function () {
     }
     return C;
 }());
-var abstract = ;
 var D = (function () {
     function D() {
     }

tests/baselines/reference/exportDefaultAbstractClass.js

@@ -0,0 +1,21 @@
+//// [tests/cases/compiler/exportDefaultAbstractClass.ts] ////
+
+//// [a.ts]
+export default abstract class A {}
+
+//// [b.ts]
+import A from './a'
+
+
+//// [a.js]
+"use strict";
+exports.__esModule = true;
+var A = (function () {
+    function A() {
+    }
+    return A;
+}());
+exports["default"] = A;
+//// [b.js]
+"use strict";
+exports.__esModule = true;

tests/baselines/reference/exportDefaultAbstractClass.symbols

@@ -0,0 +1,8 @@
+=== tests/cases/compiler/a.ts ===
+export default abstract class 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/exportDefaultAbstractClass.types

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

tests/cases/compiler/exportDefaultAbstractClass.ts

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