[clangd] Fix crash hovering on non-decltype trailing return

[malaperle]

Summary

More specifically, hovering on "auto" in
auto main() -> int {

return 0;

}

Signed-off-by: Marc-Andre Laperle <[e-mail]>

[malaperle]

Fix comment in test

[ilya-biryukov]

This seems ready, so putting myself in as a reviewer.
Let me know if there's more work to do and you don't want the review yet.

Thanks for the fix, just a single NIT comment.

clangd/XRefs.cpp

628

NIT: use 'auto' here, since the type is spelled explicitly in the initializer.

[malaperle]

Address comment.

[ilya-biryukov]

LGTM

[malaperle]

Thanks for the review!

clangd/XRefs.cpp

if (auto *AT = D->getType()->getContainedAutoType()) {
         DeducedType = AT->getDeducedType();
     }
     return true;
   }
 
   // Handle auto return types:
   //- auto foo() {}
   //- auto& foo() {}
+  //- auto foo() -> int {}
   //- auto foo() -> decltype(1+1) {}
   //- operator auto() const { return 10; }
   bool VisitFunctionDecl(FunctionDecl *D) {
     if (!D->getTypeSourceInfo())
       return true;
     // Loc of auto in return type (c++14).
     auto CurLoc = D->getReturnTypeSourceRange().getBegin();
     // Loc of "auto" in operator auto()
     if (CurLoc.isInvalid() && dyn_cast<CXXConversionDecl>(D))
       CurLoc = D->getTypeSourceInfo()->getTypeLoc().getBeginLoc();
     // Loc of "auto" in function with traling return type (c++11).
     if (CurLoc.isInvalid())
       CurLoc = D->getSourceRange().getBegin();
     if (CurLoc != SearchedLocation)
       return true;
 
     const AutoType *AT = D->getReturnType()->getContainedAutoType();
     if (AT && !AT->getDeducedType().isNull()) {
       DeducedType = AT->getDeducedType();
-    } else {
+    } else if (auto DT = dyn_cast<DecltypeType>(D->getReturnType())) {
       // auto in a trailing return type just points to a DecltypeType and
       // getContainedAutoType does not unwrap it.
-      const DecltypeType *DT = dyn_cast<DecltypeType>(D->getReturnType());
       if (!DT->getUnderlyingType().isNull())
         DeducedType = DT->getUnderlyingType();
+    } else if (!D->getReturnType().isNull()) {
+      DeducedType = D->getReturnType();
     }
     return true;
   }
 
   // Handle non-auto decltype, e.g.:
   // - auto foo() -> decltype(expr) {}
   // - decltype(expr);
   bool VisitDecltypeTypeLoc(DecltypeTypeLoc TL) {

unittests/clangd/XRefsTests.cpp

OneTest Tests[] = {
             }
             void foo() {
               ^decltype(auto) i = {1,2};
             }
           )cpp",
           "",
       },
       {
+          R"cpp(// simple trailing return type
+            ^auto main() -> int {
+              return 0;
+            }
+          )cpp",
+          "int",
+      },
+      {
           R"cpp(// auto function return with trailing type
             struct Bar {};
             ^auto test() -> decltype(Bar()) {
               return Bar();
             }
           )cpp",
           "struct Bar",
       },