[clang] [clang] separate recursive instantiation check from CodeSynthesisContext (PR #162224)

[via cfe-commits]

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@@ -3554,12 +3543,26 @@ namespace clang {
   }
 }
 
-bool
-Sema::InstantiateClass(SourceLocation PointOfInstantiation,
-                       CXXRecordDecl *Instantiation, CXXRecordDecl *Pattern,
-                       const MultiLevelTemplateArgumentList &TemplateArgs,
-                       TemplateSpecializationKind TSK,
-                       bool Complain) {
+bool Sema::InstantiateClass(SourceLocation PointOfInstantiation,
+                            CXXRecordDecl *Instantiation,
+                            CXXRecordDecl *Pattern,
+                            const MultiLevelTemplateArgumentList &TemplateArgs,
+                            TemplateSpecializationKind TSK, bool Complain) {
+#ifndef NDEBUG
+  RecursiveInstGuard AlreadyInstantiating(*this, Instantiation,
+                                          RecursiveInstGuard::Kind::Template);
+  assert(!AlreadyInstantiating && "should have been caught by caller");
+#endif
+
+  return InstantiateClassImpl(PointOfInstantiation, Instantiation, Pattern,
+                              TemplateArgs, TSK, Complain);
+}
+
+bool Sema::InstantiateClassImpl(
+    SourceLocation PointOfInstantiation, CXXRecordDecl *Instantiation,
+    CXXRecordDecl *Pattern, const MultiLevelTemplateArgumentList &TemplateArgs,
+    TemplateSpecializationKind TSK, bool Complain) {
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h-vetinari wrote:

If the only difference between `Sema::InstantiateClass` and `Sema::InstantiateClassImpl` is a debug check that gets compiled out, is that really a strong enough reason to split the function? Or are there other plans to let these two diverge some more?

https://github.com/llvm/llvm-project/pull/162224