From 17b97ccc434ff68218dcc38fa0a9c3c610bc03bd Mon Sep 17 00:00:00 2001
From: Oleksandr T <oleksandr.tarasiuk@outlook.com>
Date: Tue, 8 Feb 2022 21:36:45 +0200
Subject: [PATCH] fix(47788): forbid convertToMappedObjectType QF in invalid
 index signatures (#47798)

---
 src/services/codefixes/convertToMappedObjectType.ts      | 9 ++++++---
 .../fourslash/codeFixConvertToMappedObjectType13.ts      | 7 +++++++
 2 files changed, 13 insertions(+), 3 deletions(-)
 create mode 100644 tests/cases/fourslash/codeFixConvertToMappedObjectType13.ts

diff --git a/src/services/codefixes/convertToMappedObjectType.ts b/src/services/codefixes/convertToMappedObjectType.ts
index 340fcf2257c..7f9f6af4e80 100644
--- a/src/services/codefixes/convertToMappedObjectType.ts
+++ b/src/services/codefixes/convertToMappedObjectType.ts
@@ -25,9 +25,12 @@ namespace ts.codefix {
     interface Info { readonly indexSignature: IndexSignatureDeclaration; readonly container: FixableDeclaration; }
     function getInfo(sourceFile: SourceFile, pos: number): Info | undefined {
         const token = getTokenAtPosition(sourceFile, pos);
-        const indexSignature = cast(token.parent.parent, isIndexSignatureDeclaration);
-        if (isClassDeclaration(indexSignature.parent)) return undefined;
-        const container = isInterfaceDeclaration(indexSignature.parent) ? indexSignature.parent : cast(indexSignature.parent.parent, isTypeAliasDeclaration);
+        const indexSignature = tryCast(token.parent.parent, isIndexSignatureDeclaration);
+        if (!indexSignature) return undefined;
+
+        const container = isInterfaceDeclaration(indexSignature.parent) ? indexSignature.parent : tryCast(indexSignature.parent.parent, isTypeAliasDeclaration);
+        if (!container) return undefined;
+
         return { indexSignature, container };
     }
 
diff --git a/tests/cases/fourslash/codeFixConvertToMappedObjectType13.ts b/tests/cases/fourslash/codeFixConvertToMappedObjectType13.ts
new file mode 100644
index 00000000000..c5655f99f58
--- /dev/null
+++ b/tests/cases/fourslash/codeFixConvertToMappedObjectType13.ts
@@ -0,0 +1,7 @@
+/// <reference path='fourslash.ts' />
+
+////let x: {
+////    [p: ""]: string;
+////}
+
+verify.not.codeFixAvailable("fixConvertToMappedObjectType");