[clangd] Add a #include completion test that triggers an assertion.

Summary: Test for https://reviews.llvm.org/D52774.

Reviewers: sammccall

Reviewed By: sammccall

Subscribers: ilya-biryukov, ioeric, MaskRay, jkorous, arphaman, kadircet, cfe-commits

Differential Revision: https://reviews.llvm.org/D52775

llvm-svn: 343593

clang-tools-extra/unittests/clangd/CodeCompleteTests.cpp

@@ -2093,6 +2093,15 @@ TEST(CompletionTest, IncludedCompletionKinds) {
                     Has("bar.h\"", CompletionItemKind::File)));
 }
 
+TEST(CompletionTest, NoCrashAtNonAlphaIncludeHeader) {
+  auto Results = completions(
+      R"cpp(
+        #include "./^"
+      )cpp"
+      );
+  EXPECT_TRUE(Results.Completions.empty());
+}
+
 TEST(CompletionTest, NoAllScopesCompletionWhenQualified) {
   clangd::CodeCompleteOptions Opts = {};
   Opts.AllScopes = true;