[clang] [clang][ASTImporter] Invalidate ImportedTypes cache on Decl import failure (PR #214008)

[Balázs Benics via cfe-commits]

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@@ -6608,6 +6608,43 @@ TEST_P(ErrorHandlingTest, ErrorIsPropagatedFromMemberToClass) {
   EXPECT_FALSE(ImportedOK);
 }
 
+// A member whose signature refers back to the enclosing class (e.g. a
+// copy constructor's `const Self&` parameter) can succeed and cache the
+// class's *type* before a later, failing member causes the class's own
+// Decl import to fail as a whole. Check that this doesn't leave a stale,
+// "successfully imported" entry for the class's type behind: any later,
+// independent request to import that type must also fail, not silently
+// hand back the half-built class.
+TEST_P(ErrorHandlingTest, ImportedTypeCacheIsInvalidatedOnFailure) {
+  TranslationUnitDecl *FromTU = getTuDecl(std::string(R"(
+      class X {
+        void ok(const X &) {}          // Succeeds; imports X's own type
+                                        // as a side effect, before X's
+                                        // own import is known to fail.
+        void bad() { )") + ErroneousStmt + R"( }  // Fails to import.
+      };
+      )",
+                                          Lang_CXX03);
+  auto *FromX = FirstDeclMatcher<CXXRecordDecl>().match(
+      FromTU, cxxRecordDecl(hasName("X")));
+
+  CXXRecordDecl *ImportedX = Import(FromX, Lang_CXX03);
+  EXPECT_FALSE(ImportedX); // X itself fails to import.
+
+  // The bug: without the fix, a later, independent request to import X's
+  // type silently succeeds, returning the half-built X as if nothing had
+  // gone wrong, because ASTImporter::ImportedTypes was never scrubbed
+  // when X's own Decl import failed.
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steakhal wrote:

This (`The bug:`) seems like an artifact of an agent. In code, we should always state the current status and not refer to past bugs. If we were doing that we would only have comments in software.

https://github.com/llvm/llvm-project/pull/214008