Add flag to verify just-emitted module interfaces

The driver can now schedule jobs which typecheck just-emitted module interfaces to ensure that they can be consumed later. This can be enabled manually by passing `-verify-emitted-module-interface` to the driver.

include/swift/Driver/Action.h

@@ -51,9 +51,10 @@ public:
     GenerateDSYMJob,
     VerifyDebugInfoJob,
     GeneratePCHJob,
+    VerifyModuleInterfaceJob,
 
     JobFirst = CompileJob,
-    JobLast = GeneratePCHJob
+    JobLast = VerifyModuleInterfaceJob
   };
 
   static const char *getClassName(Kind AC);
@@ -357,6 +358,26 @@ public:
   }
 };
 
+class VerifyModuleInterfaceJobAction : public JobAction {
+  virtual void anchor();
+  file_types::ID inputType;
+
+public:
+  VerifyModuleInterfaceJobAction(const Action * ModuleEmitter,
+                                 file_types::ID inputType)
+    : JobAction(Action::Kind::VerifyModuleInterfaceJob, { ModuleEmitter },
+                file_types::TY_Nothing), inputType(inputType) {
+    assert(inputType == file_types::TY_SwiftModuleInterfaceFile ||
+           inputType == file_types::TY_PrivateSwiftModuleInterfaceFile);
+  }
+
+  file_types::ID getInputType() const { return inputType; }
+
+  static bool classof(const Action *A) {
+    return A->getKind() == Action::Kind::VerifyModuleInterfaceJob;
+  }
+};
+
 } // end namespace driver
 } // end namespace swift
 

include/swift/Driver/ToolChain.h

@@ -162,6 +162,9 @@ protected:
   virtual InvocationInfo
   constructInvocation(const VerifyDebugInfoJobAction &job,
                       const JobContext &context) const;
+  virtual InvocationInfo
+  constructInvocation(const VerifyModuleInterfaceJobAction &job,
+                      const JobContext &context) const;
   virtual InvocationInfo constructInvocation(const GeneratePCHJobAction &job,
                                              const JobContext &context) const;
   virtual InvocationInfo

include/swift/Option/Options.td

@@ -460,6 +460,15 @@ def emit_private_module_interface_path :
          DoesNotAffectIncrementalBuild, ArgumentIsPath, SupplementaryOutput]>,
   MetaVarName<"<path>">, HelpText<"Output private module interface file to <path>">;
 
+def verify_emitted_module_interface :
+  Flag<["-"], "verify-emitted-module-interface">,
+  Flags<[NoInteractiveOption, DoesNotAffectIncrementalBuild]>,
+  HelpText<"Check that module interfaces emitted during compilation typecheck">;
+def no_verify_emitted_module_interface :
+  Flag<["-"], "no-verify-emitted-module-interface">,
+  Flags<[NoInteractiveOption, DoesNotAffectIncrementalBuild]>,
+  HelpText<"Don't check that module interfaces emitted during compilation typecheck">;
+
 def avoid_emit_module_source_info :
   Flag<["-"], "avoid-emit-module-source-info">,
   Flags<[NoInteractiveOption, DoesNotAffectIncrementalBuild]>,

lib/Driver/Action.cpp

@@ -33,6 +33,7 @@ const char *Action::getClassName(Kind AC) {
   case Kind::GenerateDSYMJob:  return "generate-dSYM";
   case Kind::VerifyDebugInfoJob:  return "verify-debug-info";
   case Kind::GeneratePCHJob:  return "generate-pch";
+  case Kind::VerifyModuleInterfaceJob: return "verify-module-interface";
   }
 
   llvm_unreachable("invalid class");
@@ -65,3 +66,5 @@ void GenerateDSYMJobAction::anchor() {}
 void VerifyDebugInfoJobAction::anchor() {}
 
 void GeneratePCHJobAction::anchor() {}
+
+void VerifyModuleInterfaceJobAction::anchor() {}

lib/Driver/Driver.cpp

@@ -2208,6 +2208,26 @@ void Driver::buildActions(SmallVectorImpl<const Action *> &TopLevelActions,
       TopLevelActions.push_back(MergeModuleAction);
     TopLevelActions.append(AllLinkerInputs.begin(), AllLinkerInputs.end());
   }
+
+  bool verifyInterfacesByDefault = false;
+
+  if (MergeModuleAction
+      && Args.hasFlag(options::OPT_verify_emitted_module_interface,
+                      options::OPT_no_verify_emitted_module_interface,
+                      verifyInterfacesByDefault)) {
+    if (Args.hasArgNoClaim(options::OPT_emit_module_interface,
+                           options::OPT_emit_module_interface_path)) {
+      TopLevelActions.push_back(
+          C.createAction<VerifyModuleInterfaceJobAction>(MergeModuleAction,
+              file_types::TY_SwiftModuleInterfaceFile));
+    }
+
+    if (Args.hasArgNoClaim(options::OPT_emit_private_module_interface_path)) {
+      TopLevelActions.push_back(
+          C.createAction<VerifyModuleInterfaceJobAction>(MergeModuleAction,
+              file_types::TY_PrivateSwiftModuleInterfaceFile));
+    }
+  }
 }
 
 bool Driver::handleImmediateArgs(const ArgList &Args, const ToolChain &TC) {

lib/Driver/ToolChain.cpp

@@ -111,6 +111,7 @@ std::unique_ptr<Job> ToolChain::constructJob(
       CASE(GeneratePCHJob)
       CASE(AutolinkExtractJob)
       CASE(REPLJob)
+      CASE(VerifyModuleInterfaceJob)
 #undef CASE
     case Action::Kind::Input:
       llvm_unreachable("not a JobAction");

lib/Driver/ToolChains.cpp

@@ -1047,6 +1047,41 @@ ToolChain::constructInvocation(const MergeModuleJobAction &job,
   return II;
 }
 
+ToolChain::InvocationInfo
+ToolChain::constructInvocation(const VerifyModuleInterfaceJobAction &job,
+                               const JobContext &context) const {
+  InvocationInfo II{SWIFT_EXECUTABLE_NAME};
+  ArgStringList &Arguments = II.Arguments;
+  II.allowsResponseFiles = true;
+
+  for (auto &s : getDriver().getSwiftProgramArgs())
+    Arguments.push_back(s.c_str());
+  Arguments.push_back("-frontend");
+
+  Arguments.push_back("-typecheck-module-from-interface");
+
+  size_t sizeBefore = Arguments.size();
+  addInputsOfType(Arguments, context.Inputs, context.Args, job.getInputType());
+
+  (void)sizeBefore;
+  assert(Arguments.size() - sizeBefore == 1 &&
+         "should verify exactly one module interface per job");
+
+  addCommonFrontendArgs(context.OI, context.Output, context.Args, Arguments);
+  addRuntimeLibraryFlags(context.OI, Arguments);
+
+  addOutputsOfType(Arguments, context.Output, context.Args,
+                   file_types::TY_SerializedDiagnostics,
+                   "-serialize-diagnostics-path");
+
+  context.Args.AddLastArg(Arguments, options::OPT_import_objc_header);
+
+  Arguments.push_back("-module-name");
+  Arguments.push_back(context.Args.MakeArgString(context.OI.ModuleName));
+
+  return II;
+}
+
 ToolChain::InvocationInfo
 ToolChain::constructInvocation(const ModuleWrapJobAction &job,
                                const JobContext &context) const {

test/ModuleInterface/verify-module-interfaces.swift

@@ -0,0 +1,15 @@
+// RUN: %empty-directory(%t)
+
+// Check that verification won't reject a valid interface:
+// RUN: %target-build-swift -emit-library -enable-library-evolution -emit-module-interface -emit-module -swift-version 5 -o %t/MyModule.o -verify-emitted-module-interface -module-name MyModule %s
+
+// Check that verification will reject an invalid interface:
+// RUN: not %target-build-swift -emit-library -enable-library-evolution -emit-module-interface -emit-module -swift-version 5 -o %t/MyModule.o -verify-emitted-module-interface -module-name MyModule -Xfrontend -debug-emit-invalid-swiftinterface-syntax %s 2>&1 | %FileCheck %s
+
+// ...but not if verification is off.
+// RUN: %target-build-swift -emit-library -enable-library-evolution -emit-module-interface -emit-module -swift-version 5 -o %t/MyModule.o -no-verify-emitted-module-interface -module-name MyModule -Xfrontend -debug-emit-invalid-swiftinterface-syntax %s
+
+public struct MyStruct {}
+
+// CHECK: MyModule.swiftinterface:{{[0-9]+}}:{{[0-9]+}}: error: use of unknown directive '#__debug_emit_invalid_swiftinterface_syntax__'
+// CHECK: MyModule.swiftinterface:{{[0-9]+}}:{{[0-9]+}}: error: failed to build module 'MyModule' from its module interface; it may have been damaged or it may have triggered a bug in the Swift compiler when it was produced