Merge pull request swiftlang#36723 from CodaFi/extension-cord

Add a Null Check for Missing Generic Signatures

Author: CodaFi

lib/AST/DeclContext.cpp

@@ -1188,7 +1188,9 @@ bool DeclContext::hasValueSemantics() const {
 bool DeclContext::isClassConstrainedProtocolExtension() const {
   if (getExtendedProtocolDecl()) {
     auto ED = cast<ExtensionDecl>(this);
-    return ED->getGenericSignature()->requiresClass(ED->getSelfInterfaceType());
+    if (auto sig = ED->getGenericSignature()) {
+      return sig->requiresClass(ED->getSelfInterfaceType());
+    }
   }
   return false;
 }

validation-test/compiler_crashers_2_fixed/rdar76049852.swift

@@ -0,0 +1,14 @@
+// RUN: not %target-swift-frontend -typecheck %s
+
+struct MyStruct {}
+protocol MyProtocol {}
+
+func foo(bytes: [MyStruct]) {
+  bytes.withUnsafeBufferPointer { a in
+    extension MyProtocol {
+      var bytes: MyStruct {
+        fatalError()
+      }
+    }
+  }
+}