[LLD][COFF] Store __imp_ symbols as Defined in InputFile

lld/COFF/InputFiles.h

@@ -349,7 +349,7 @@ class ImportFile : public InputFile {
   MachineTypes getMachineType() const override;
 
   DefinedImportData *impSym = nullptr;
-  Symbol *thunkSym = nullptr;
+  Defined *thunkSym = nullptr;
   ImportThunkChunkARM64EC *impchkThunk = nullptr;
   std::string dllName;
 
@@ -365,7 +365,7 @@ class ImportFile : public InputFile {
   // Auxiliary IAT symbols and chunks on ARM64EC.
   DefinedImportData *impECSym = nullptr;
   Chunk *auxLocation = nullptr;
-  Symbol *auxThunkSym = nullptr;
+  Defined *auxThunkSym = nullptr;
   DefinedImportData *auxImpCopySym = nullptr;
   Chunk *auxCopyLocation = nullptr;
 

lld/COFF/MapFile.cpp

@@ -128,8 +128,7 @@ static void getSymbols(const COFFLinkerContext &ctx,
     if (!file->thunkSym->isLive())
       continue;
 
-    if (auto *thunkSym = dyn_cast<Defined>(file->thunkSym))
-      syms.push_back(thunkSym);
+    syms.push_back(file->thunkSym);
 
     if (auto *impSym = dyn_cast_or_null<Defined>(file->impSym))
       syms.push_back(impSym);

lld/COFF/SymbolTable.cpp

@@ -823,13 +823,13 @@ DefinedImportData *SymbolTable::addImportData(StringRef n, ImportFile *f,
   return nullptr;
 }
 
-Symbol *SymbolTable::addImportThunk(StringRef name, DefinedImportData *id,
-                                    ImportThunkChunk *chunk) {
+Defined *SymbolTable::addImportThunk(StringRef name, DefinedImportData *id,
+                                     ImportThunkChunk *chunk) {
   auto [s, wasInserted] = insert(name, nullptr);
   s->isUsedInRegularObj = true;
   if (wasInserted || isa<Undefined>(s) || s->isLazy()) {
     replaceSymbol<DefinedImportThunk>(s, ctx, name, id, chunk);
-    return s;
+    return cast<Defined>(s);
   }
 
   reportDuplicate(s, id->file);

lld/COFF/SymbolTable.h

@@ -105,8 +105,8 @@ class SymbolTable {
                     CommonChunk *c = nullptr);
   DefinedImportData *addImportData(StringRef n, ImportFile *f,
                                    Chunk *&location);
-  Symbol *addImportThunk(StringRef name, DefinedImportData *s,
-                         ImportThunkChunk *chunk);
+  Defined *addImportThunk(StringRef name, DefinedImportData *s,
+                          ImportThunkChunk *chunk);
   void addLibcall(StringRef name);
   void addEntryThunk(Symbol *from, Symbol *to);
   void addExitThunk(Symbol *from, Symbol *to);