[clang][Interp] Don't create Records for incomplete decls

We would previously create the Record instance with 0 fields,
which is incorrect. We later see it again with 1 field.

Fixes llvm#82203

Author: tbaederr

clang/lib/AST/Interp/Program.cpp

@@ -232,6 +232,9 @@ Record *Program::getOrCreateRecord(const RecordDecl *RD) {
   if (!RD)
     return nullptr;
 
+  if (!RD->isCompleteDefinition())
+    return nullptr;
+
   // Deduplicate records.
   if (auto It = Records.find(RD); It != Records.end())
     return It->second;

clang/test/AST/Interp/lambda.cpp

@@ -222,3 +222,16 @@ namespace GH62611 {
     return 0;
   }
 }
+
+namespace LambdaToAPValue {
+  void wrapper() {
+    constexpr auto f = []() constexpr {
+      return 0;
+    };
+
+    constexpr auto g = [f]() constexpr {
+      return f();
+    };
+    static_assert(g() == f(), "");
+  }
+}