[clang] [Clang][Interp] Fix display of syntactically-invalid note for member function calls (PR #102170)

[Timm Baeder via cfe-commits]

================
@@ -198,11 +198,11 @@ def NoRet : Opcode {}
 
 
 def Call : Opcode {
-  let Args = [ArgFunction, ArgUint32];
+  let Args = [ArgFunction, ArgUint32, ArgExpr];
----------------
tbaederr wrote:

You forgot the `This && IsMemberCall` check from the current interpreter.
Consider these diffs:
```diff
+
+   const Expr *MyCE = Caller->getExpr(getRetPC());
+   assert(MyCE == CallExpr);
+
   const FunctionDecl *F = getCallee();
-  if (const auto *M = dyn_cast<CXXMethodDecl>(F);
-      M && M->isInstance() && !isa<CXXConstructorDecl>(F)) {
-    print(OS, This, S.getCtx(), S.getCtx().getRecordType(M->getParent()));
-    OS << "->";
+  assert(F);
+
+  bool IsMemberCall =
+      isa<CXXMethodDecl>(F) && !isa<CXXConstructorDecl>(F) &&
+      cast<CXXMethodDecl>(F)->isImplicitObjectMemberFunction();
+
+  assert(Caller);
+
+  if (Func->hasThisPointer() && IsMemberCall) {
+    if (const auto *MCE = dyn_cast_if_present<CXXMemberCallExpr>(MyCE)) {
+      const Expr *Object = MCE->getImplicitObjectArgument();
+      Object->printPretty(OS, /*Helper=*/nullptr, S.getCtx().getPrintingPolicy(),
+                          /*Indentation=*/0);
+      if (Object->getType()->isPointerType())
+        OS << "->";
+      else
+        OS << ".";
+    } else if (const auto *OCE =
+                   dyn_cast_if_present<CXXOperatorCallExpr>(MyCE)) {
+      OCE->getArg(0)->printPretty(OS, /*Helper=*/nullptr,
+                                  S.getCtx().getPrintingPolicy(),
+                                  /*Indentation=*/0);
+      OS << ".";
+    }
```

```diff
diff --git a/clang/lib/AST/Interp/Source.cpp b/clang/lib/AST/Interp/Source.cpp
index 45cd0ad4fd42..77796b00ca52 100644
--- a/clang/lib/AST/Interp/Source.cpp
+++ b/clang/lib/AST/Interp/Source.cpp
@@ -41,7 +41,7 @@ const Expr *SourceInfo::asExpr() const {
 const Expr *SourceMapper::getExpr(const Function *F, CodePtr PC) const {
   if (const Expr *E = getSource(F, PC).asExpr())
     return E;
-  llvm::report_fatal_error("missing source expression");
+  return nullptr;
 }
```

I'll have to rebuild llvm locally now because I figured out the `llvm::report_fatal_error` above just trips my build up.

https://github.com/llvm/llvm-project/pull/102170