diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -531,6 +531,9 @@
 - Fixed a failing assertion when applying an attribute to an anonymous union.
   The assertion was benign outside of asserts builds and would only fire in C++.
   (`#48512 <https://github.com/llvm/llvm-project/issues/48512>_`).
+- Stop evaluating a constant expression if the condition expression which in 
+  switch statement contains errors.
+  (`#63453 <https://github.com/llvm/llvm-project/issues/63453>_`)
 
 Bug Fixes to Compiler Builtins
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -5007,7 +5007,9 @@
     APSInt LHS = CS->getLHS()->EvaluateKnownConstInt(Info.Ctx);
     APSInt RHS = CS->getRHS() ? CS->getRHS()->EvaluateKnownConstInt(Info.Ctx)
                               : LHS;
-    if (LHS <= Value && Value <= RHS) {
+    if (Value.getBitWidth() == LHS.getBitWidth() &&
+        Value.getBitWidth() == RHS.getBitWidth() && LHS <= Value &&
+        Value <= RHS) {
       Found = SC;
       break;
     }
diff --git a/clang/test/SemaCXX/switch.cpp b/clang/test/SemaCXX/switch.cpp
--- a/clang/test/SemaCXX/switch.cpp
+++ b/clang/test/SemaCXX/switch.cpp
@@ -1,4 +1,5 @@
 // RUN: %clang_cc1 -fsyntax-only -verify -std=c++11 %s
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++17 %s
 
 void test() {
   bool x = true;
@@ -146,3 +147,17 @@
 }
 
 } // namespace EmptyEnum
+
+#if __cplusplus >= 201703L
+constexpr int foo(unsigned char c) {
+    switch (unknown_value) { // expected-error {{use of undeclared identifier}}
+    case 0:
+        return 7;
+    default:
+        break;
+    }
+    return 0;
+}
+
+static_assert(foo('d')); // expected-error {{static assertion expression is not an integral constant expression}}
+#endif