[clang-tidy] Treat references to smart pointers correctly in use-after-move.

[mboehme]

Summary

Previously, we weren't recognizing these as smart pointers and thus
weren't allowing non-dereference accesses as we should -- see new test
cases which fail without the fix.

[mboehme]

Removing experimental code that shouldn't have been added.

[JonasToth]

LGTM, is there a bug report for this issue? If yes please close that too :)

[mboehme]

In D56585#1358477, @JonasToth wrote:

LGTM, is there a bug report for this issue? If yes please close that too :)

Thanks for the reminder!

This was a bug that was reported internally, so there is no LLVM bug for this.

clang-tidy/bugprone/UseAfterMoveCheck.cpp

void UseAfterMoveFinder::getUsesAndReinits(
   // Sort the uses by their occurrence in the source code.
   std::sort(Uses->begin(), Uses->end(),
             [](const DeclRefExpr *D1, const DeclRefExpr *D2) {
               return D1->getExprLoc() < D2->getExprLoc();
             });
 }
 
 bool isStandardSmartPointer(const ValueDecl *VD) {
-  const Type *TheType = VD->getType().getTypePtrOrNull();
+  const Type *TheType = VD->getType().getNonReferenceType().getTypePtrOrNull();
   if (!TheType)
     return false;
 
   const CXXRecordDecl *RecordDecl = TheType->getAsCXXRecordDecl();
   if (!RecordDecl)
     return false;
 
   const IdentifierInfo *ID = RecordDecl->getIdentifier();

test/clang-tidy/bugprone-use-after-move.cpp

void standardSmartPtr() {
   {
     struct B {
       typedef A AnotherNameForA;
     };
     std::unique_ptr<B::AnotherNameForA> ptr;
     std::move(ptr);
     ptr.get();
   }
+  // Make sure we treat references to smart pointers correctly.
+  {
+    std::unique_ptr<A> ptr;
+    std::unique_ptr<A>& ref_to_ptr = ptr;
+    std::move(ref_to_ptr);
+    ref_to_ptr.get();
+  }
+  {
+    std::unique_ptr<A> ptr;
+    std::unique_ptr<A>&& rvalue_ref_to_ptr = std::move(ptr);
+    std::move(rvalue_ref_to_ptr);
+    rvalue_ref_to_ptr.get();
+  }
   // We don't give any special treatment to types that are called "unique_ptr"
   // or "shared_ptr" but are not in the "::std" namespace.
   {
     struct unique_ptr {
       void get();
     } ptr;
     std::move(ptr);
     ptr.get();
     // CHECK-NOTES: [[@LINE-1]]:5: warning: 'ptr' used after it was moved
     // CHECK-NOTES: [[@LINE-3]]:5: note: move occurred here
   }
 }
 
+void foo(std::unique_ptr<A>&& a) {
+  std::move(a);
+  std::move(a);
+}
+
 // The check also works in member functions.
 class Container {
   void useAfterMoveInMemberFunction() {
     A a;
     std::move(a);
     a.foo();
     // CHECK-NOTES: [[@LINE-1]]:5: warning: 'a' used after it was moved
     // CHECK-NOTES: [[@LINE-3]]:5: note: move occurred here