Merge pull request #4502 from Microsoft/fixClassExtendsNullDeclEmit

Fixes declaration emit for a class that extends null

src/compiler/declarationEmitter.ts

@@ -896,6 +896,9 @@ namespace ts {
                 if (isSupportedExpressionWithTypeArguments(node)) {
                     emitTypeWithNewGetSymbolAccessibilityDiagnostic(node, getHeritageClauseVisibilityError);
                 }
+                else if (!isImplementsList && node.expression.kind === SyntaxKind.NullKeyword) {
+                    write("null");
+                }
 
                 function getHeritageClauseVisibilityError(symbolAccesibilityResult: SymbolAccessiblityResult): SymbolAccessibilityDiagnostic {
                     let diagnosticMessage: DiagnosticMessage;

tests/baselines/reference/declFileClassExtendsNull.js

@@ -0,0 +1,23 @@
+//// [declFileClassExtendsNull.ts]
+
+class ExtendsNull extends null {
+}
+
+//// [declFileClassExtendsNull.js]
+var __extends = (this && this.__extends) || function (d, b) {
+    for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
+    function __() { this.constructor = d; }
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
+};
+var ExtendsNull = (function (_super) {
+    __extends(ExtendsNull, _super);
+    function ExtendsNull() {
+        _super.apply(this, arguments);
+    }
+    return ExtendsNull;
+})(null);
+
+
+//// [declFileClassExtendsNull.d.ts]
+declare class ExtendsNull extends null {
+}

tests/baselines/reference/declFileClassExtendsNull.symbols

@@ -0,0 +1,5 @@
+=== tests/cases/compiler/declFileClassExtendsNull.ts ===
+
+class ExtendsNull extends null {
+>ExtendsNull : Symbol(ExtendsNull, Decl(declFileClassExtendsNull.ts, 0, 0))
+}

tests/baselines/reference/declFileClassExtendsNull.types

@@ -0,0 +1,6 @@
+=== tests/cases/compiler/declFileClassExtendsNull.ts ===
+
+class ExtendsNull extends null {
+>ExtendsNull : ExtendsNull
+>null : null
+}

tests/cases/compiler/declFileClassExtendsNull.ts

@@ -0,0 +1,5 @@
+// @target: ES5
+// @declaration: true
+
+class ExtendsNull extends null {
+}