[Type checker] Check “bridged functions” as part of type checking setup.

The “check bridged functions” hack makes sure that certain functions
provided by the Darwin and ObjectiveC overlays and used by SILGen
get interface types. Perform “check bridged functions” as part of the
general “type check a source file” routine. This eliminates some state
from TypeChecker (the “have we checked yet?” bit) so we can take
TypeChecker out of more of @objc checking.

Author: DougGregor

lib/Sema/TypeCheckDeclObjC.cpp

@@ -928,24 +928,19 @@ static void checkObjCBridgingFunctions(ModuleDecl *mod,
   }
 }
 
-static void checkBridgedFunctions(TypeChecker &TC) {
-  if (TC.HasCheckedBridgeFunctions)
-    return;
-
-  TC.HasCheckedBridgeFunctions = true;
-
+void swift::checkBridgedFunctions(ASTContext &ctx) {
   #define BRIDGE_TYPE(BRIDGED_MOD, BRIDGED_TYPE, _, NATIVE_TYPE, OPT) \
-  Identifier ID_##BRIDGED_MOD = TC.Context.getIdentifier(#BRIDGED_MOD);\
-  if (ModuleDecl *module = TC.Context.getLoadedModule(ID_##BRIDGED_MOD)) {\
+  Identifier ID_##BRIDGED_MOD = ctx.getIdentifier(#BRIDGED_MOD);\
+  if (ModuleDecl *module = ctx.getLoadedModule(ID_##BRIDGED_MOD)) {\
     checkObjCBridgingFunctions(module, #BRIDGED_TYPE, \
     "_convert" #BRIDGED_TYPE "To" #NATIVE_TYPE, \
     "_convert" #NATIVE_TYPE "To" #BRIDGED_TYPE); \
   }
   #include "swift/SIL/BridgedTypes.def"
 
-  if (ModuleDecl *module = TC.Context.getLoadedModule(TC.Context.Id_Foundation)) {
+  if (ModuleDecl *module = ctx.getLoadedModule(ctx.Id_Foundation)) {
     checkObjCBridgingFunctions(module,
-                               TC.Context.getSwiftName(
+                               ctx.getSwiftName(
                                  KnownFoundationEntity::NSError),
                                "_convertNSErrorToError",
                                "_convertErrorToNSError");
@@ -1434,9 +1429,6 @@ void swift::markAsObjC(TypeChecker &TC, ValueDecl *D,
     attr->setInvalid();
   }
 
-  // Make sure we have the appropriate bridging operations.
-  if (!isa<DestructorDecl>(D))
-    checkBridgedFunctions(TC);
   TC.useObjectiveCBridgeableConformances(D->getInnermostDeclContext(),
                                          D->getInterfaceType());
 

lib/Sema/TypeCheckObjC.h

@@ -137,6 +137,11 @@ bool isRepresentableInObjC(const SubscriptDecl *SD, ObjCReason Reason);
 /// Check whether the given declaration can be represented in Objective-C.
 bool canBeRepresentedInObjC(const ValueDecl *decl);
 
+/// Check that specific, known bridging functions are fully type-checked.
+///
+/// NOTE: This is only here to support the --enable-source-import hack.
+void checkBridgedFunctions(ASTContext &ctx);
+
 } // end namespace swift
 
 #endif // SWIFT_SEMA_TYPE_CHECK_OBJC_H

lib/Sema/TypeChecker.cpp

@@ -17,6 +17,7 @@
 
 #include "swift/Subsystems.h"
 #include "TypeChecker.h"
+#include "TypeCheckObjC.h"
 #include "CodeSynthesis.h"
 #include "MiscDiagnostics.h"
 #include "GenericTypeResolver.h"
@@ -670,6 +671,10 @@ void swift::performTypeChecking(SourceFile &SF, TopLevelContext &TLC,
       }
     });
 
+    // Look for bridging functions. This only matters when
+    // -enable-source-import is provided.
+    checkBridgedFunctions(TC.Context);
+
     // Type check the top-level elements of the source file.
     bool hasTopLevelCode = false;
     for (auto D : llvm::makeArrayRef(SF.Decls).slice(StartElem)) {

lib/Sema/TypeChecker.h

@@ -678,11 +678,6 @@ class TypeChecker final : public LazyResolver {
   llvm::DenseMap<std::pair<ValueDecl*, ValueDecl*>, bool> 
     specializedOverloadComparisonCache;
 
-  // We delay validation of C and Objective-C type-bridging functions in the
-  // standard library until we encounter a declaration that requires one. This
-  // flag is set to 'true' once the bridge functions have been checked.
-  bool HasCheckedBridgeFunctions = false;
-
   /// A list of closures for the most recently type-checked function, which we
   /// will need to compute captures for.
   std::vector<AnyFunctionRef> ClosuresWithUncomputedCaptures;