From 22076ecd963ccec1c040875b6a53fa22fb7ffbbc Mon Sep 17 00:00:00 2001
From: Andrew Branch <andrew@wheream.io>
Date: Mon, 12 Oct 2020 12:49:23 -0700
Subject: [PATCH] Fix auto imports for export default edge cases

---
 src/services/codefixes/importFixes.ts           |  8 +++++++-
 .../importNameCodeFixDefaultExport6.ts          | 17 +++++++++++++++++
 .../importNameCodeFixDefaultExport7.ts          | 14 ++++++++++++++
 3 files changed, 38 insertions(+), 1 deletion(-)
 create mode 100644 tests/cases/fourslash/importNameCodeFixDefaultExport6.ts
 create mode 100644 tests/cases/fourslash/importNameCodeFixDefaultExport7.ts

diff --git a/src/services/codefixes/importFixes.ts b/src/services/codefixes/importFixes.ts
index 065d4112d7d10..407903390efb9 100644
--- a/src/services/codefixes/importFixes.ts
+++ b/src/services/codefixes/importFixes.ts
@@ -622,7 +622,13 @@ namespace ts.codefix {
 
         if (defaultExport.flags & SymbolFlags.Alias) {
             const aliased = checker.getImmediateAliasedSymbol(defaultExport);
-            return aliased && getDefaultExportInfoWorker(aliased, Debug.checkDefined(aliased.parent, "Alias targets of default exports must have a parent"), checker, compilerOptions);
+            if (aliased && aliased.parent) {
+                // - `aliased` will be undefined if the module is exporting an unresolvable name,
+                //    but we can still offer completions for it.
+                // - `aliased.parent` will be undefined if the module is exporting `globalThis.something`,
+                //    or another expression that resolves to a global.
+                return getDefaultExportInfoWorker(aliased, aliased.parent, checker, compilerOptions);
+            }
         }
 
         if (defaultExport.escapedName !== InternalSymbolName.Default &&
diff --git a/tests/cases/fourslash/importNameCodeFixDefaultExport6.ts b/tests/cases/fourslash/importNameCodeFixDefaultExport6.ts
new file mode 100644
index 0000000000000..2dcea116f592a
--- /dev/null
+++ b/tests/cases/fourslash/importNameCodeFixDefaultExport6.ts
@@ -0,0 +1,17 @@
+/// <reference path="fourslash.ts" />
+
+// @Filename: /a.ts
+//// export default Math.foo;
+
+// @Filename: /index.ts
+//// a/**/
+
+verify.applyCodeActionFromCompletion("", {
+  name: "a",
+  source: "/a",
+  description: `Import default 'a' from module "./a"`,
+  newFileContent: `import a from "./a";\n\na`,
+  preferences: {
+    includeCompletionsForModuleExports: true
+  }
+});
diff --git a/tests/cases/fourslash/importNameCodeFixDefaultExport7.ts b/tests/cases/fourslash/importNameCodeFixDefaultExport7.ts
new file mode 100644
index 0000000000000..05311abba2e2d
--- /dev/null
+++ b/tests/cases/fourslash/importNameCodeFixDefaultExport7.ts
@@ -0,0 +1,14 @@
+/// <reference path="fourslash.ts" />
+
+// @lib: dom
+
+// @Filename: foo.ts
+//// export default globalThis.localStorage;
+
+// @Filename: index.ts
+//// foo/**/
+
+goTo.marker("");
+verify.importFixAtPosition([`import foo from "./foo";
+
+foo`]);