[FrontendTool] Only validate TBD for Swift input.

lib/FrontendTool/FrontendTool.cpp

@@ -925,6 +925,9 @@ static bool performCompile(CompilerInstance &Instance,
     allSymbols = true;
     LLVM_FALLTHROUGH;
   case FrontendOptions::TBDValidationMode::MissingFromTBD: {
+    if (!inputFileKindCanHaveTBDValidated(Invocation.getInputKind()))
+      break;
+
     auto hasMultipleIRGenThreads = Invocation.getSILOptions().NumThreads > 1;
     bool error;
     if (PrimarySourceFile)

lib/FrontendTool/TBD.cpp

@@ -60,6 +60,21 @@ bool swift::writeTBD(ModuleDecl *M, bool hasMultipleIRGenThreads,
   return false;
 }
 
+bool swift::inputFileKindCanHaveTBDValidated(InputFileKind kind) {
+  // Only things that involve an AST can have a TBD file computed, at the
+  // moment.
+  switch (kind) {
+  case InputFileKind::IFK_Swift:
+  case InputFileKind::IFK_Swift_Library:
+    return true;
+  case InputFileKind::IFK_None:
+  case InputFileKind::IFK_Swift_REPL:
+  case InputFileKind::IFK_SIL:
+  case InputFileKind::IFK_LLVM_IR:
+    return false;
+  }
+}
+
 static bool validateSymbolSet(DiagnosticEngine &diags,
                               llvm::StringSet<> symbols, llvm::Module &IRModule,
                               bool diagnoseExtraSymbolsInTBD) {

lib/FrontendTool/TBD.h

@@ -13,6 +13,8 @@
 #ifndef SWIFT_FRONTENDTOOL_TBD_H
 #define SWIFT_FRONTENDTOOL_TBD_H
 
+#include "swift/Frontend/FrontendOptions.h"
+
 namespace llvm {
 class StringRef;
 class Module;
@@ -24,6 +26,7 @@ class FrontendOptions;
 
 bool writeTBD(ModuleDecl *M, bool hasMultipleIRGenThreads,
               llvm::StringRef OutputFilename);
+bool inputFileKindCanHaveTBDValidated(InputFileKind kind);
 bool validateTBD(ModuleDecl *M, llvm::Module &IRModule,
                  bool hasMultipleIRGenThreads, bool diagnoseExtraSymbolsInTBD);
 bool validateTBD(FileUnit *M, llvm::Module &IRModule,