[clangd] Move the selection decltype hack to getSourceRange.

Previously, it was in canSafelySkipNode, which is only used to decide
whether we should descend into it and its children, and we still used
the incomplete Decltypeloc.getSourceRange() to claim tokens, which will
cause some tokens were not claimed correctly.

Separate a change of https://reviews.llvm.org/D116536

Reviewed By: sammccall

Differential Revision: https://reviews.llvm.org/D116586

Author: hokein

clang-tools-extra/clangd/Selection.cpp

@@ -60,6 +60,21 @@ void recordMetrics(const SelectionTree &S, const LangOptions &Lang) {
 
 // Return the range covering a node and all its children.
 SourceRange getSourceRange(const DynTypedNode &N) {
+  // DeclTypeTypeLoc::getSourceRange() is incomplete, which would lead to
+  // failing to descend into the child expression.
+  // decltype(2+2);
+  // ~~~~~~~~~~~~~ <-- correct range
+  // ~~~~~~~~      <-- range reported by getSourceRange()
+  // ~~~~~~~~~~~~  <-- range with this hack(i.e, missing closing paren)
+  // FIXME: Alter DecltypeTypeLoc to contain parentheses locations and get
+  // rid of this patch.
+  if (const auto *TL = N.get<TypeLoc>()) {
+    if (auto DT = TL->getAs<DecltypeTypeLoc>()) {
+      SourceRange S = DT.getSourceRange();
+      S.setEnd(DT.getUnderlyingExpr()->getEndLoc());
+      return S;
+    }
+  }
   // MemberExprs to implicitly access anonymous fields should not claim any
   // tokens for themselves. Given:
   //   struct A { struct { int b; }; };
@@ -647,17 +662,6 @@ class SelectionVisitor : public RecursiveASTVisitor<SelectionVisitor> {
       // heuristics. We should consider only pruning critical TypeLoc nodes, to
       // be more robust.
 
-      // DeclTypeTypeLoc::getSourceRange() is incomplete, which would lead to
-      // failing
-      // to descend into the child expression.
-      // decltype(2+2);
-      // ~~~~~~~~~~~~~ <-- correct range
-      // ~~~~~~~~      <-- range reported by getSourceRange()
-      // ~~~~~~~~~~~~  <-- range with this hack(i.e, missing closing paren)
-      // FIXME: Alter DecltypeTypeLoc to contain parentheses locations and get
-      // rid of this patch.
-      if (auto DT = TL->getAs<DecltypeTypeLoc>())
-        S.setEnd(DT.getUnderlyingExpr()->getEndLoc());
       // AttributedTypeLoc may point to the attribute's range, NOT the modified
       // type's range.
       if (auto AT = TL->getAs<AttributedTypeLoc>())

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

@@ -385,6 +385,7 @@ TEST(SelectionTest, CommonAncestor) {
         decltype([[^a]] + a) b;
         )cpp",
           "DeclRefExpr"},
+      {"[[decltype]]^(1) b;", "DecltypeTypeLoc"}, // Not the VarDecl.
 
       // Objective-C nullability attributes.
       {