[clangd] Fix a crash when presenting values for Hover

[ilya-biryukov]

Summary

We should pass the expression type, not a variable type when printing
the resulting value. Variable type may be different from what the
pretty-printing function expects, e.g. have references.

[ilya-biryukov]

@hans, could we merge this commit into the release branch?

[hans]

In D65655#1612392, @ilya-biryukov wrote:

@hans, could we merge this commit into the release branch?

Sure, merged in r367807.

clang-tools-extra/trunk/clangd/XRefs.cpp

static HoverInfo getHoverContents(const Decl *D, const SymbolIndex *Index) {
   // function calls.
   if (const auto *Var = dyn_cast<VarDecl>(D)) {
     if (const Expr *Init = Var->getInit()) {
       Expr::EvalResult Result;
       if (!Init->isValueDependent() && Init->EvaluateAsRValue(Result, Ctx)) {
         HI.Value.emplace();
         llvm::raw_string_ostream ValueOS(*HI.Value);
         Result.Val.printPretty(ValueOS, const_cast<ASTContext &>(Ctx),
-                               Var->getType());
+                               Init->getType());
       }
     }
   }
 
   HI.Definition = printDefinition(D);
   enhanceFromIndex(HI, D, Index);
   return HI;
 }

clang-tools-extra/trunk/clangd/unittests/XRefsTests.cpp

])cpp",
           R"cpp(// More compilcated structured types.
             int bar();
             ^auto (*foo)() = bar;
           )cpp",
           "codeblock(cpp) [\n"
           "int\n"
           "]",
       },
+      {
+          R"cpp(// Should not crash when evaluating the initializer.
+            struct Test {};
+            void test() { Test && te^st = {}; }
+          )cpp",
+          "text[Declared in]code[test]\n"
+          "codeblock(cpp) [\n"
+          "struct Test &&test = {}\n"
+          "]",
+      },
   };
 
   // Create a tiny index, so tests above can verify documentation is fetched.
   Symbol IndexSym = func("indexSymbol");
   IndexSym.Documentation = "comment from index";
   SymbolSlab::Builder Symbols;
   Symbols.insert(IndexSym);
   auto Index =