fix: Handle missing definition on member lookup (#330)

Author: varungandhi-src

indexer/ApproximateNameResolver.cc

@@ -6,6 +6,7 @@
 #include "llvm/ADT/SmallVector.h"
 
 #include "indexer/ApproximateNameResolver.h"
+#include "indexer/DebugHelpers.h"
 #include "indexer/Enforce.h"
 
 #include "spdlog/spdlog.h"
@@ -44,9 +45,10 @@ ApproximateNameResolver::tryResolveMember(
     auto *type = typesToLookup.back();
     typesToLookup.pop_back();
     auto *cxxRecordDecl = Self::tryFindDeclForType(type);
-    if (!cxxRecordDecl) {
+    if (!cxxRecordDecl || !cxxRecordDecl->hasDefinition()) {
       continue;
     }
+    cxxRecordDecl = cxxRecordDecl->getDefinition();
     auto lookupResults =
         cxxRecordDecl->lookupDependentName(declNameInfo.getName(), filter);
     for (auto *namedDecl : lookupResults) {

test/index/functions/templates.cc

@@ -58,4 +58,21 @@ struct Q2: Q1<T> {
   using Base2 = Q1<T>;
   using Base2::f;
   void h() { f(); }
+};
+
+template <typename T>
+struct FwdDecl1;
+
+template <typename T>
+struct FwdDecl2;
+
+template <typename X>
+void f(FwdDecl1<X> &a1, FwdDecl2<X> &a2) {
+  a1.whatever(); // No code nav, sorry
+  a2.whatever();
+}
+
+template <typename T>
+struct FwdDecl2 {
+  void whatever() {}
 };

test/index/functions/templates.snapshot.cc

@@ -136,3 +136,38 @@
 //       ^ definition [..] Q2#h(49f6e7a06ebc5aa8).
 //             ^ reference [..] Q0#f(49f6e7a06ebc5aa8).
   };
+  
+  template <typename T>
+//                   ^ definition local 14
+  struct FwdDecl1;
+//       ^^^^^^^^ reference [..] FwdDecl1#
+  
+  template <typename T>
+//                   ^ definition local 15
+  struct FwdDecl2;
+//       ^^^^^^^^ reference [..] FwdDecl2#
+  
+  template <typename X>
+//                   ^ definition local 16
+  void f(FwdDecl1<X> &a1, FwdDecl2<X> &a2) {
+//     ^ definition [..] f(4764f947061d9ce0).
+//       ^^^^^^^^ reference [..] FwdDecl1#
+//                ^ reference local 16
+//                    ^^ definition local 17
+//                        ^^^^^^^^ reference [..] FwdDecl2#
+//                                 ^ reference local 16
+//                                     ^^ definition local 18
+    a1.whatever(); // No code nav, sorry
+//  ^^ reference local 17
+    a2.whatever();
+//  ^^ reference local 18
+//     ^^^^^^^^ reference [..] FwdDecl2#whatever(49f6e7a06ebc5aa8).
+  }
+  
+  template <typename T>
+//                   ^ definition local 19
+  struct FwdDecl2 {
+//       ^^^^^^^^ definition [..] FwdDecl2#
+    void whatever() {}
+//       ^^^^^^^^ definition [..] FwdDecl2#whatever(49f6e7a06ebc5aa8).
+  };