[clang] 133b6d7 - [clang][C++20] Fix clang/clangd assert/crash after compilation errors

[Dmitry Polukhin via cfe-commits]

Author: Dmitry Polukhin
Date: 2022-09-17T07:37:19-07:00
New Revision: 133b6d7db90d9b52b01e8e09e1aa8fb8d2da0f9d

URL: https://github.com/llvm/llvm-project/commit/133b6d7db90d9b52b01e8e09e1aa8fb8d2da0f9d
DIFF: https://github.com/llvm/llvm-project/commit/133b6d7db90d9b52b01e8e09e1aa8fb8d2da0f9d.diff

LOG: [clang][C++20] Fix clang/clangd assert/crash after compilation errors

After compilation errors, expression a transformation result may not be usable.
It triggers an assert in RemoveNestedImmediateInvocation and SIGSEGV in case of
builds without asserts. This issue significantly affects clangd because source
may not be valid during typing. Tests cases that I attached was reduce from huge
C++ translation unit.

Test Plan: check-clang

Differential Revision: https://reviews.llvm.org/D133948

Added: 
    clang/test/SemaCXX/remove-nested-immediate-invocation-crash.cpp

Modified: 
    clang/lib/Sema/SemaExpr.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index e53c88b283b8..b49b7ce45cf4 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -17624,9 +17624,13 @@ static void RemoveNestedImmediateInvocation(
     Transformer.AllowSkippingFirstCXXConstructExpr = false;
 
   ExprResult Res = Transformer.TransformExpr(It->getPointer()->getSubExpr());
-  assert(Res.isUsable());
-  Res = SemaRef.MaybeCreateExprWithCleanups(Res);
-  It->getPointer()->setSubExpr(Res.get());
+  // The result may not be usable in case of previous compilation errors.
+  // In this case evaluation of the expression may result in crash so just
+  // don't do anything further with the result.
+  if (Res.isUsable()) {
+    Res = SemaRef.MaybeCreateExprWithCleanups(Res);
+    It->getPointer()->setSubExpr(Res.get());
+  }
 }
 
 static void

diff  --git a/clang/test/SemaCXX/remove-nested-immediate-invocation-crash.cpp b/clang/test/SemaCXX/remove-nested-immediate-invocation-crash.cpp
new file mode 100644
index 000000000000..26faf2bc1c06
--- /dev/null
+++ b/clang/test/SemaCXX/remove-nested-immediate-invocation-crash.cpp
@@ -0,0 +1,11 @@
+// RUN: not %clang_cc1 -fsyntax-only -verify -std=gnu++20 -ferror-limit 19 %s
+// Creduced test case for the crash in RemoveNestedImmediateInvocation after compliation errros.
+
+a, class b {                               template < typename c>                 consteval b(c
+} template <typename...> using d = b;
+auto e(d<>) -> int:;
+}
+f
+}
+g() {
+                    auto h = "":(::i(e(h))