fix: Correctly emit refs for local extern decls (#362)

Author: varungandhi-src

indexer/Indexer.cc

@@ -860,24 +860,29 @@ void TuIndexer::saveVarDecl(const clang::VarDecl &varDecl) {
     // Individual bindings will be visited by VisitBindingDecl
     return;
   }
+#define GET_SYMBOL                                              \
+  auto optSymbol = this->symbolFormatter.getVarSymbol(varDecl); \
+  if (!optSymbol.has_value()) {                                 \
+    return;                                                     \
+  }
+  auto loc = varDecl.getLocation();
+  if (varDecl.isLocalExternDecl()) {
+    GET_SYMBOL;
+    this->saveReference(*optSymbol, loc, &varDecl);
+    return;
+  }
   if (varDecl.isLocalVarDeclOrParm()) {
-    auto optSymbol = this->symbolFormatter.getLocalVarOrParmSymbol(varDecl);
-    if (!optSymbol.has_value()) {
-      return;
-    }
-    this->saveDefinition(optSymbol.value(), varDecl.getLocation(),
-                         std::nullopt);
+    GET_SYMBOL;
+    this->saveDefinition(*optSymbol, loc, std::nullopt);
   }
   if (varDecl.isStaticDataMember() || varDecl.isFileVarDecl()) {
+    GET_SYMBOL;
     // Non-static data members are handled by saveFieldDecl
-    auto optSymbol = this->symbolFormatter.getVarSymbol(varDecl);
-    if (!optSymbol.has_value()) {
-      return;
-    }
     scip::SymbolInformation symbolInfo{};
     this->getDocComment(varDecl).addTo(symbolInfo);
-    this->saveDefinition(optSymbol.value(), varDecl.getLocation(), symbolInfo);
+    this->saveDefinition(*optSymbol, loc, symbolInfo);
   }
+#undef GET_SYMBOL
 }
 
 void TuIndexer::saveVarTemplateDecl(const clang::VarTemplateDecl &) {

indexer/SymbolFormatter.cc

@@ -705,7 +705,7 @@ SymbolFormatter::getUsingSymbol(const clang::UsingDecl &) {
 
 std::optional<SymbolNameRef>
 SymbolFormatter::getVarSymbol(const clang::VarDecl &varDecl) {
-  if (varDecl.isLocalVarDeclOrParm()) {
+  if (varDecl.isLocalVarDeclOrParm() && !varDecl.isLocalExternDecl()) {
     return this->getLocalVarOrParmSymbol(varDecl);
   }
   if (varDecl.getDeclName().isEmpty()) {

test/index/fwd_decl/mydefs.cc

@@ -7,3 +7,5 @@ struct S {};
 void C::m() { }
 
 int Global = 3;
+
+int externInt = 30;

test/index/fwd_decl/mydefs.snapshot.cc

@@ -14,3 +14,6 @@
 
   int Global = 3;
 //    ^^^^^^ definition [..] Global.
+  
+  int externInt = 30;
+//    ^^^^^^^^^ definition [..] externInt.

test/index/fwd_decl/myuses.cc

@@ -10,3 +10,8 @@ void doStuff(S *, C *c) {
     undo_magic();
   }
 }
+
+int useExtern() {
+  extern int externInt;
+  return externInt;
+}

test/index/fwd_decl/myuses.snapshot.cc

@@ -23,3 +23,11 @@
 //    ^^^^^^^^^^ reference [..] undo_magic(49f6e7a06ebc5aa8).
     }
   }
+  
+  int useExtern() {
+//    ^^^^^^^^^ definition [..] useExtern(b126dc7c1de90089).
+    extern int externInt;
+//             ^^^^^^^^^ reference [..] externInt.
+    return externInt;
+//         ^^^^^^^^^ reference [..] externInt.
+  }