[clangd] Fix hover crashing on null types

[kadircet]

Summary

Fixes https://github.com/clangd/clangd/issues/225

[ilya-biryukov]

clang-tools-extra/clangd/Hover.cpp

251

NIT: Replace T.isNull() with !T

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

517

Why is the type null here?

[ilya-biryukov]

Wow, ParenListExpr is a really weird construct...

[ilya-biryukov]

LGTM

[merge_guards_bot]

Unit tests: fail. 60654 tests passed, 1 failed and 726 were skipped.

failed: lld.ELF/linkerscript/provide-empty-section.s

clang-format: pass.

Build artifacts: console-log.txt, CMakeCache.txt, test-results.xml, diff.json

[kadircet]

clang-tools-extra/clangd/Hover.cpp

251

I don't think ! is defined for QualType.

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

517

because parentlistexprs, as you've noticed

clang-tools-extra/clangd/Hover.cpp

if (const auto* CCD = llvm::dyn_cast<CXXConstructorDecl>(FD)) {
     QualType FunctionType = FD->getType();
     if (const VarDecl *VD = llvm::dyn_cast<VarDecl>(D)) // Lambdas
       FunctionType = VD->getType().getDesugaredType(D->getASTContext());
     HI.Type = FunctionType.getAsString(Policy);
   }
   // FIXME: handle variadics.
 }
 
-llvm::Optional<std::string> printExprValue(const Expr *E, const ASTContext &Ctx) {
+llvm::Optional<std::string> printExprValue(const Expr *E,
+                                           const ASTContext &Ctx) {
   Expr::EvalResult Constant;
   // Evaluating [[foo]]() as "&foo" isn't useful, and prevents us walking up
   // to the enclosing call.
   QualType T = E->getType();
-  if (T->isFunctionType() || T->isFunctionPointerType() ||
+  if (T.isNull() || T->isFunctionType() || T->isFunctionPointerType() ||
       T->isFunctionReferenceType())
     return llvm::None;
   // Attempt to evaluate. If expr is dependent, evaluation crashes!
   if (E->isValueDependent() || !E->EvaluateAsRValue(Constant, Ctx))
     return llvm::None;
 
   // Show enums symbolically, not numerically like APValue::printPretty().
   if (T->isEnumeralType() && Constant.Val.getInt().getMinSignedBits() <= 64) {

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

void foo())cpp";
        [](HoverInfo &HI) {
          HI.Name = "bar";
          HI.Definition = "const char *bar = \"1234\"";
          HI.Kind = index::SymbolKind::Variable;
          HI.Type = "const char *";
          HI.NamespaceScope = "";
          HI.Value = "&\"1234\"[0]";
        }},
+      {R"cpp(// Should not crash
+        template <typename T>
+        struct Tmpl {
+          Tmpl(int name);
+        };
+
+        template <typename A>
+        void boom(int name) {
+          new Tmpl<A>([[na^me]]);
+        })cpp",
+       [](HoverInfo &HI) {
+         HI.Name = "name";
+         HI.Definition = "int name";
+         HI.Kind = index::SymbolKind::Parameter;
+         HI.Type = "int";
+         HI.NamespaceScope = "";
+         HI.LocalScope = "boom::";
+       }},
   };
   for (const auto &Case : Cases) {
     SCOPED_TRACE(Case.Code);
 
     Annotations T(Case.Code);
     TestTU TU = TestTU::withCode(T.code());
     TU.ExtraArgs.push_back("-std=c++17");
     auto AST = TU.build();