[clangd] Include expression in DecltypeTypeLoc sourcerange while building SelectionTree

Summary:
Currently AST only contains the location for `decltype` keyword,
therefore we were skipping expressions inside decltype while building selection
tree.

This patch extends source range in such cases to contain the expression as well.
A proper fix would require changes to Sema and DecltypeTypeLoc to contain these
location information.

Fixes https://github.com/clangd/clangd/issues/250.

Reviewers: sammccall

Subscribers: ilya-biryukov, MaskRay, jkorous, arphaman, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D72594

1 files changed, 6 insertions, 0 deletions

diff --git a/clang-tools-extra/clangd/unittests/SelectionTests.cpp b/clang-tools-extra/clangd/unittests/SelectionTests.cpp
index 9e1a90b55e3..581309b1dcc 100644
--- a/clang-tools-extra/clangd/unittests/SelectionTests.cpp
+++ b/clang-tools-extra/clangd/unittests/SelectionTests.cpp
@@ -323,6 +323,12 @@ TEST(SelectionTest, CommonAncestor) {
             Foo x = [[^12_ud]];
           )cpp",
           "UserDefinedLiteral"},
+      {
+          R"cpp(
+        int a;
+        decltype([[^a]] + a) b;
+        )cpp",
+          "DeclRefExpr"},
   };
   for (const Case &C : Cases) {
     Annotations Test(C.Code);