[clangd] Ignore cvr-qualifiers in selection.

The AST doesn't track their locations, and the default behavior of attributing
them to the lexically-enclosing node is sloppy and often inaccurate.

Also add a couple of passing test cases for declarators that weren't obvious.

Differential Revision: https://reviews.llvm.org/D117185

clang-tools-extra/clangd/Selection.cpp

@@ -188,7 +188,19 @@ void update(SelectionTree::Selection &Result, SelectionTree::Selection New) {
 // As well as comments, don't count semicolons as real tokens.
 // They're not properly claimed as expr-statement is missing from the AST.
 bool shouldIgnore(const syntax::Token &Tok) {
-  return Tok.kind() == tok::comment || Tok.kind() == tok::semi;
+  switch (Tok.kind()) {
+    // Even "attached" comments are not considered part of a node's range.
+    case tok::comment:
+    // The AST doesn't directly store locations for terminating semicolons.
+    case tok::semi:
+    // We don't have locations for cvr-qualifiers: see QualifiedTypeLoc.
+    case tok::kw_const:
+    case tok::kw_volatile:
+    case tok::kw_restrict:
+      return true;
+    default:
+      return false;
+  }
 }
 
 // Determine whether 'Target' is the first expansion of the macro

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

@@ -331,9 +331,17 @@ TEST(SelectionTest, CommonAncestor) {
 
       {"int (*getFunc([[do^uble]]))(int);", "BuiltinTypeLoc"},
 
+      // Member pointers and pack expansion use declarator syntax, but are
+      // restricted so they don't need special casing.
+      {"class X{}; [[int X::^*]]y[10];", "MemberPointerTypeLoc"},
+      {"template<typename ...T> void foo([[T*^...]]x);",
+       "PackExpansionTypeLoc"},
+      {"template<typename ...T> void foo([[^T]]*...x);",
+       "TemplateTypeParmTypeLoc"},
+
       // FIXME: the AST has no location info for qualifiers.
       {"const [[a^uto]] x = 42;", "AutoTypeLoc"},
-      {"[[co^nst auto x = 42]];", "VarDecl"},
+      {"co^nst auto x = 42;", nullptr},
 
       {"^", nullptr},
       {"void foo() { [[foo^^]] (); }", "DeclRefExpr"},