Fix export default expression comment (microsoft#48323)

Author: xiaoxiangmoe

src/compiler/transformers/declarations.ts

@@ -1140,6 +1140,9 @@ namespace ts {
                         const varDecl = factory.createVariableDeclaration(newId, /*exclamationToken*/ undefined, resolver.createTypeOfExpression(input.expression, input, declarationEmitNodeBuilderFlags, symbolTracker), /*initializer*/ undefined);
                         errorFallbackNode = undefined;
                         const statement = factory.createVariableStatement(needsDeclare ? [factory.createModifier(SyntaxKind.DeclareKeyword)] : [], factory.createVariableDeclarationList([varDecl], NodeFlags.Const));
+
+                        preserveJsDoc(statement, input);
+                        removeAllComments(input);
                         return [statement, factory.updateExportAssignment(input, input.decorators, input.modifiers, newId)];
                     }
                 }

tests/baselines/reference/exportDefaultExpressionComments.js

@@ -0,0 +1,22 @@
+//// [exportDefaultExpressionComments.ts]
+/**
+ * JSDoc Comments
+ */
+export default null
+
+
+//// [exportDefaultExpressionComments.js]
+"use strict";
+exports.__esModule = true;
+/**
+ * JSDoc Comments
+ */
+exports["default"] = null;
+
+
+//// [exportDefaultExpressionComments.d.ts]
+/**
+ * JSDoc Comments
+ */
+declare const _default: any;
+export default _default;

tests/baselines/reference/exportDefaultExpressionComments.symbols

@@ -0,0 +1,7 @@
+=== tests/cases/conformance/declarationEmit/exportDefaultExpressionComments.ts ===
+/**
+No type information for this code. * JSDoc Comments
+No type information for this code. */
+No type information for this code.export default null
+No type information for this code.
+No type information for this code.

tests/baselines/reference/exportDefaultExpressionComments.types

@@ -0,0 +1,7 @@
+=== tests/cases/conformance/declarationEmit/exportDefaultExpressionComments.ts ===
+/**
+ * JSDoc Comments
+ */
+export default null
+>null : null
+

tests/cases/conformance/declarationEmit/exportDefaultExpressionComments.ts

@@ -0,0 +1,6 @@
+// @declaration: true
+
+/**
+ * JSDoc Comments
+ */
+export default null