diff --git a/lld/wasm/SymbolTable.cpp b/lld/wasm/SymbolTable.cpp
index d8d7be9..b9f4e6e 100644
--- a/lld/wasm/SymbolTable.cpp
+++ b/lld/wasm/SymbolTable.cpp
@@ -71,63 +71,56 @@
   return {Sym, true};
 }
 
+static void reportTypeError(const Symbol *Existing, const InputFile *File,
+                            StringRef Type) {
+  error("symbol type mismatch: " + toString(*Existing) + "\n>>> defined as " +
+        toString(Existing->getWasmType()) + " in " +
+        toString(Existing->getFile()) + "\n>>> defined as " + Type + " in " +
+        toString(File));
+}
+
+static void checkFunctionType(const Symbol *Existing, const InputFile *File,
+                              const WasmSignature *NewSig) {
+  if (!isa<FunctionSymbol>(Existing)) {
+    reportTypeError(Existing, File, "Function");
+    return;
+  }
+
+  if (!Config->CheckSignatures)
+    return;
+
+  const WasmSignature *OldSig =
+      cast<FunctionSymbol>(Existing)->getFunctionType();
+  if (OldSig && *NewSig != *OldSig) {
+    error("Function type mismatch: " + Existing->getName() +
+          "\n>>> defined as " + toString(*OldSig) + " in " +
+          toString(Existing->getFile()) + "\n>>> defined as " +
+          toString(*NewSig) + " in " + toString(File));
+  }
+}
+
 // Check the type of new symbol matches that of the symbol is replacing.
 // For functions this can also involve verifying that the signatures match.
-static void checkSymbolTypes(const Symbol &Existing, const InputFile &F,
-                             WasmSymbolType NewType,
-                             const WasmSignature *NewFunctionSig,
-                             const WasmGlobalType *NewGlobalType) {
-  if (Existing.isLazy())
-    return;
-
-  WasmSymbolType ExistingType = Existing.getWasmType();
-
-  // First check the symbol types match (i.e. either both are function
-  // symbols or both are data symbols).
-  if (NewType != ExistingType) {
-    error("symbol type mismatch: " + Existing.getName() + "\n>>> defined as " +
-          toString(ExistingType) + " in " + toString(Existing.getFile()) +
-          "\n>>> defined as " + toString(NewType) + " in " + F.getName());
+static void checkGlobalType(const Symbol *Existing, const InputFile *File,
+                            const WasmGlobalType *NewType) {
+  if (!isa<GlobalSymbol>(Existing)) {
+    reportTypeError(Existing, File, "Global");
     return;
   }
 
-  // For function/global symbols, optionally check the type matches too.
-  if (NewType == WASM_SYMBOL_TYPE_DATA || !Config->CheckSignatures)
-    return;
-
-  DEBUG(dbgs() << "checkSymbolTypes: " << Existing.getName() << "\n");
-
-  auto ReportError = [&](const Twine &Old, const Twine &New) {
-    error(toString(NewType) + " type mismatch: " + Existing.getName() +
-          "\n>>> defined as " + Old + " in " + toString(Existing.getFile()) +
-          "\n>>> defined as " + New + " in " + F.getName());
-  };
-
-  if (NewType == WASM_SYMBOL_TYPE_FUNCTION) {
-    // Skip the signature check if the existing function has no signature (e.g.
-    // if it is an undefined symbol generated by --undefined command line flag).
-    auto &Sym = cast<FunctionSymbol>(Existing);
-    const WasmSignature *OldSig = Sym.getFunctionType();
-    if (!OldSig)
-      return;
-
-    assert(NewFunctionSig);
-    if (*NewFunctionSig == *OldSig)
-      return;
-
-    ReportError(toString(*OldSig), toString(*NewFunctionSig));
-  } else {
-    auto &Sym = cast<GlobalSymbol>(Existing);
-
-    assert(NewGlobalType != nullptr);
-    const WasmGlobalType *OldType = Sym.getGlobalType();
-    if (*NewGlobalType == *OldType)
-      return;
-
-    ReportError(toString(*OldType), toString(*NewGlobalType));
+  const WasmGlobalType *OldType = cast<GlobalSymbol>(Existing)->getGlobalType();
+  if (*NewType != *OldType) {
+    error("Global type mismatch: " + Existing->getName() + "\n>>> defined as " +
+          toString(*OldType) + " in " + toString(Existing->getFile()) +
+          "\n>>> defined as " + toString(*NewType) + " in " + toString(File));
   }
 }
 
+static void checkDataType(const Symbol *Existing, const InputFile *File) {
+  if (!isa<DataSymbol>(Existing))
+    reportTypeError(Existing, File, "Data");
+}
+
 DefinedFunction *SymbolTable::addSyntheticFunction(StringRef Name,
                                                    const WasmSignature *Type,
                                                    uint32_t Flags) {
@@ -159,29 +152,12 @@
   return replaceSymbol<DefinedGlobal>(S, Name, Flags, nullptr, Global);
 }
 
-static bool shouldReplace(const Symbol &Existing, InputFile *NewFile,
-                          WasmSymbolType NewType, uint32_t NewFlags,
-                          const WasmSignature *NewFuncType = nullptr,
-                          const WasmGlobalType *NewGlobalType = nullptr) {
-
-  // If existing symbol is lazy, replace it without checking types since
-  // lazy symbols don't have any type information.
-  if (Existing.isLazy()) {
-    DEBUG(dbgs() << "replacing existing lazy symbol: " << Existing.getName()
-                 << "\n");
-    return true;
-  }
-
-  // Now we have two wasm symbols, and all wasm symbols that have the same
-  // symbol name must have the same type, even if they are undefined. This
-  // is different from ELF because symbol types are not that significant
-  // in ELF, and undefined symbols in ELF don't have type in the first place.
-  checkSymbolTypes(Existing, *NewFile, NewType, NewFuncType, NewGlobalType);
-
+static bool shouldReplace(const Symbol *Existing, InputFile *NewFile,
+                          uint32_t NewFlags) {
   // If existing symbol is undefined, replace it.
-  if (!Existing.isDefined()) {
+  if (!Existing->isDefined()) {
     DEBUG(dbgs() << "resolving existing undefined symbol: "
-                 << Existing.getName() << "\n");
+                 << Existing->getName() << "\n");
     return true;
   }
 
@@ -192,93 +168,131 @@
   }
 
   // If the existing symbol is weak, we should replace it.
-  if (Existing.isWeak()) {
+  if (Existing->isWeak()) {
     DEBUG(dbgs() << "replacing existing weak symbol\n");
     return true;
   }
 
   // Neither symbol is week. They conflict.
-  error("duplicate symbol: " + toString(Existing) + "\n>>> defined in " +
-        toString(Existing.getFile()) + "\n>>> defined in " + toString(NewFile));
+  error("duplicate symbol: " + toString(*Existing) + "\n>>> defined in " +
+        toString(Existing->getFile()) + "\n>>> defined in " +
+        toString(NewFile));
   return true;
 }
 
 Symbol *SymbolTable::addDefinedFunction(StringRef Name, uint32_t Flags,
-                                        InputFile *F, InputFunction *Function) {
+                                        InputFile *File,
+                                        InputFunction *Function) {
   DEBUG(dbgs() << "addDefinedFunction: " << Name << "\n");
   Symbol *S;
   bool WasInserted;
   std::tie(S, WasInserted) = insert(Name);
-  if (WasInserted || shouldReplace(*S, F, WASM_SYMBOL_TYPE_FUNCTION, Flags,
-                                   &Function->Signature))
-    replaceSymbol<DefinedFunction>(S, Name, Flags, F, Function);
+
+  if (WasInserted || S->isLazy()) {
+    replaceSymbol<DefinedFunction>(S, Name, Flags, File, Function);
+    return S;
+  }
+
+  checkFunctionType(S, File, &Function->Signature);
+
+  if (shouldReplace(S, File, Flags))
+    replaceSymbol<DefinedFunction>(S, Name, Flags, File, Function);
   return S;
 }
 
 Symbol *SymbolTable::addDefinedData(StringRef Name, uint32_t Flags,
-                                    InputFile *F, InputSegment *Segment,
+                                    InputFile *File, InputSegment *Segment,
                                     uint32_t Address, uint32_t Size) {
   DEBUG(dbgs() << "addDefinedData:" << Name << " addr:" << Address << "\n");
   Symbol *S;
   bool WasInserted;
   std::tie(S, WasInserted) = insert(Name);
-  if (WasInserted || shouldReplace(*S, F, WASM_SYMBOL_TYPE_DATA, Flags))
-    replaceSymbol<DefinedData>(S, Name, Flags, F, Segment, Address, Size);
+
+  if (WasInserted || S->isLazy()) {
+    replaceSymbol<DefinedData>(S, Name, Flags, File, Segment, Address, Size);
+    return S;
+  }
+
+  checkDataType(S, File);
+
+  if (shouldReplace(S, File, Flags))
+    replaceSymbol<DefinedData>(S, Name, Flags, File, Segment, Address, Size);
   return S;
 }
 
 Symbol *SymbolTable::addDefinedGlobal(StringRef Name, uint32_t Flags,
-                                      InputFile *F, InputGlobal *Global) {
+                                      InputFile *File, InputGlobal *Global) {
   DEBUG(dbgs() << "addDefinedGlobal:" << Name << "\n");
   Symbol *S;
   bool WasInserted;
   std::tie(S, WasInserted) = insert(Name);
-  if (WasInserted || shouldReplace(*S, F, WASM_SYMBOL_TYPE_GLOBAL, Flags,
-                                   nullptr, &Global->getType()))
-    replaceSymbol<DefinedGlobal>(S, Name, Flags, F, Global);
+
+  if (WasInserted || S->isLazy()) {
+    replaceSymbol<DefinedGlobal>(S, Name, Flags, File, Global);
+    return S;
+  }
+
+  checkGlobalType(S, File, &Global->getType());
+
+  if (shouldReplace(S, File, Flags))
+    replaceSymbol<DefinedGlobal>(S, Name, Flags, File, Global);
   return S;
 }
 
-Symbol *SymbolTable::addUndefined(StringRef Name, WasmSymbolType Type,
-                                  uint32_t Flags, InputFile *F,
-                                  const WasmSignature *FunctionType,
-                                  const WasmGlobalType *GlobalType) {
-  DEBUG(dbgs() << "addUndefined type=" << Type << ": " << Name << "\n");
+Symbol *SymbolTable::addUndefinedFunction(StringRef Name, uint32_t Flags,
+                                          InputFile *File,
+                                          const WasmSignature *Sig) {
+  DEBUG(dbgs() << "addUndefinedFunction: " << Name << "\n");
 
   Symbol *S;
   bool WasInserted;
   std::tie(S, WasInserted) = insert(Name);
 
-  if (WasInserted) {
-    switch (Type) {
-    case WASM_SYMBOL_TYPE_FUNCTION:
-      replaceSymbol<UndefinedFunction>(S, Name, Flags, F, FunctionType);
-      break;
-    case WASM_SYMBOL_TYPE_GLOBAL:
-      replaceSymbol<UndefinedGlobal>(S, Name, Flags, F, GlobalType);
-      break;
-    case WASM_SYMBOL_TYPE_DATA:
-      replaceSymbol<UndefinedData>(S, Name, Flags, F);
-      break;
-    }
-    return S;
-  }
-
-  if (auto *Lazy = dyn_cast<LazySymbol>(S)) {
-    DEBUG(dbgs() << "resolved by existing lazy\n");
+  if (WasInserted)
+    replaceSymbol<UndefinedFunction>(S, Name, Flags, File, Sig);
+  else if (auto *Lazy = dyn_cast<LazySymbol>(S))
     cast<ArchiveFile>(Lazy->getFile())->addMember(&Lazy->getArchiveSymbol());
-    return S;
-  }
-
-  if (S->isDefined()) {
-    DEBUG(dbgs() << "resolved by existing\n");
-    checkSymbolTypes(*S, *F, Type, FunctionType, GlobalType);
-  }
-
+  else if (S->isDefined())
+    checkFunctionType(S, File, Sig);
   return S;
 }
 
-void SymbolTable::addLazy(ArchiveFile *F, const Archive::Symbol *Sym) {
+Symbol *SymbolTable::addUndefinedData(StringRef Name, uint32_t Flags,
+                                      InputFile *File) {
+  DEBUG(dbgs() << "addUndefinedData: " << Name << "\n");
+
+  Symbol *S;
+  bool WasInserted;
+  std::tie(S, WasInserted) = insert(Name);
+
+  if (WasInserted)
+    replaceSymbol<UndefinedData>(S, Name, Flags, File);
+  else if (auto *Lazy = dyn_cast<LazySymbol>(S))
+    cast<ArchiveFile>(Lazy->getFile())->addMember(&Lazy->getArchiveSymbol());
+  else if (S->isDefined())
+    checkDataType(S, File);
+  return S;
+}
+
+Symbol *SymbolTable::addUndefinedGlobal(StringRef Name, uint32_t Flags,
+                                        InputFile *File,
+                                        const WasmGlobalType *Type) {
+  DEBUG(dbgs() << "addUndefinedGlobal: " << Name << "\n");
+
+  Symbol *S;
+  bool WasInserted;
+  std::tie(S, WasInserted) = insert(Name);
+
+  if (WasInserted)
+    replaceSymbol<UndefinedGlobal>(S, Name, Flags, File, Type);
+  else if (auto *Lazy = dyn_cast<LazySymbol>(S))
+    cast<ArchiveFile>(Lazy->getFile())->addMember(&Lazy->getArchiveSymbol());
+  else if (S->isDefined())
+    checkGlobalType(S, File, Type);
+  return S;
+}
+
+void SymbolTable::addLazy(ArchiveFile *File, const Archive::Symbol *Sym) {
   DEBUG(dbgs() << "addLazy: " << Sym->getName() << "\n");
   StringRef Name = Sym->getName();
 
@@ -287,14 +301,14 @@
   std::tie(S, WasInserted) = insert(Name);
 
   if (WasInserted) {
-    replaceSymbol<LazySymbol>(S, Name, F, *Sym);
+    replaceSymbol<LazySymbol>(S, Name, File, *Sym);
     return;
   }
 
   // If there is an existing undefined symbol, load a new one from the archive.
   if (S->isUndefined()) {
     DEBUG(dbgs() << "replacing existing undefined\n");
-    F->addMember(Sym);
+    File->addMember(Sym);
   }
 }