From a099275b2aa5318a67d4bb2a1ae15fe32b2997ec Mon Sep 17 00:00:00 2001
From: Andrew Branch <andrewbranch@users.noreply.github.com>
Date: Wed, 3 Jan 2024 15:46:54 -0600
Subject: [PATCH] Fix declaration emit for JS default re-exports that resolve
 to modules through synthesized default exports (#56340)

---
 src/compiler/checker.ts                        |  3 +++
 .../declarationEmitJsReExportDefault.js        | 15 +++++++++++++++
 .../declarationEmitJsReExportDefault.ts        | 18 ++++++++++++++++++
 3 files changed, 36 insertions(+)
 create mode 100644 tests/baselines/reference/declarationEmitJsReExportDefault.js
 create mode 100644 tests/cases/compiler/declarationEmitJsReExportDefault.ts

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 30c41c94d3a..7fcd96913ae 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -9744,6 +9744,9 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                         // does not use localName because the symbol name in this case refers to the name in the exports table,
                         // which we must exactly preserve
                         const specifier = (node.parent.parent as ExportDeclaration).moduleSpecifier;
+                        if (specifier && (node as ExportSpecifier).propertyName?.escapedText === InternalSymbolName.Default) {
+                            verbatimTargetName = InternalSymbolName.Default;
+                        }
                         // targetName is only used when the target is local, as otherwise the target is an alias that points at
                         // another file
                         serializeExportSpecifier(
diff --git a/tests/baselines/reference/declarationEmitJsReExportDefault.js b/tests/baselines/reference/declarationEmitJsReExportDefault.js
new file mode 100644
index 00000000000..f575575ff96
--- /dev/null
+++ b/tests/baselines/reference/declarationEmitJsReExportDefault.js
@@ -0,0 +1,15 @@
+//// [tests/cases/compiler/declarationEmitJsReExportDefault.ts] ////
+
+//// [package.json]
+{"name": "a", "version": "0.0.0"}
+//// [index.d.ts]
+export const a = 123;
+
+//// [index.mjs]
+export {default as mod} from 'a';
+
+
+
+
+//// [index.d.mts]
+export { default as mod } from "a";
diff --git a/tests/cases/compiler/declarationEmitJsReExportDefault.ts b/tests/cases/compiler/declarationEmitJsReExportDefault.ts
new file mode 100644
index 00000000000..0d05fc45d60
--- /dev/null
+++ b/tests/cases/compiler/declarationEmitJsReExportDefault.ts
@@ -0,0 +1,18 @@
+// @noTypesAndSymbols: true
+
+// @filename: /node_modules/a/package.json
+{"name": "a", "version": "0.0.0"}
+// @filename: /node_modules/a/index.d.ts
+export const a = 123;
+
+// @filename: /tsconfig.json
+{
+  "compilerOptions": {
+    "module": "node16",
+    "declaration": true,
+    "emitDeclarationOnly": true,
+    "checkJs": true,
+  }
+}
+// @filename: /index.mjs
+export {default as mod} from 'a';