Implement SE-0075: CanImport

include/swift/AST/ASTContext.h

@@ -262,6 +262,9 @@ class ASTContext {
   llvm::DenseMap<const Pattern *, DeclContext *>
     DelayedPatternContexts;
 
+  /// Cache of module names that fail the 'canImport' test in this context.
+  llvm::SmallPtrSet<Identifier, 8> FailedModuleImportNames;
+
 public:
   /// \brief Retrieve the allocator for the given arena.
   llvm::BumpPtrAllocator &

include/swift/Basic/LangOptions.h

@@ -43,8 +43,9 @@ namespace swift {
     Endianness,
     /// Runtime support (_ObjC or _Native)
     Runtime,
+    /// Conditional import of module
+    CanImport,
   };
-  enum { NumPlatformConditionKind = 4 };
 
   /// Describes which Swift 3 Objective-C inference warnings should be
   /// emitted.
@@ -341,8 +342,7 @@ namespace swift {
     }
 
   private:
-    llvm::SmallVector<std::pair<PlatformConditionKind, std::string>,
-                      NumPlatformConditionKind>
+    llvm::SmallVector<std::pair<PlatformConditionKind, std::string>, 4>
         PlatformConditionValues;
     llvm::SmallVector<std::string, 2> CustomConditionalCompilationFlags;
   };

include/swift/Frontend/Frontend.h

@@ -426,7 +426,9 @@ class CompilerInstance {
 
   /// Parses the input file but does no type-checking or module imports.
   /// Note that this only supports parsing an invocation with a single file.
-  void performParseOnly();
+  ///
+  ///
+  void performParseOnly(bool EvaluateConditionals = false);
 
   /// Frees up the ASTContext and SILModule objects that this instance is
   /// holding on.

include/swift/Parse/PersistentParserState.h

@@ -98,7 +98,9 @@ class PersistentParserState {
   };
 
   bool InPoundLineEnvironment = false;
-
+  // FIXME: When condition evaluation moves to a later phase, remove this bit
+  // and adjust the client call 'performParseOnly'.
+  bool PerformConditionEvaluation = true;
 private:
   ScopeInfo ScopeInfo;
   typedef llvm::DenseMap<AbstractFunctionDecl *,

lib/AST/ASTContext.cpp

@@ -1458,12 +1458,18 @@ bool ASTContext::canImportModule(std::pair<Identifier, SourceLoc> ModulePath) {
   if (getLoadedModule(ModulePath) != nullptr)
     return true;
 
+  // If we've failed loading this module before, don't look for it again.
+  if (FailedModuleImportNames.count(ModulePath.first))
+    return false;
+
   // Otherwise, ask the module loaders.
   for (auto &importer : Impl.ModuleLoaders) {
     if (importer->canImportModule(ModulePath)) {
       return true;
     }
   }
+
+  FailedModuleImportNames.insert(ModulePath.first);
   return false;
 }
 

lib/Basic/LangOptions.cpp

@@ -98,6 +98,10 @@ checkPlatformConditionSupported(PlatformConditionKind Kind, StringRef Value,
   case PlatformConditionKind::Runtime:
     return contains(SupportedConditionalCompilationRuntimes, Value,
                     suggestions);
+  case PlatformConditionKind::CanImport:
+    // All importable names are valid.
+    // FIXME: Perform some kind of validation of the string?
+    return true;
   }
   llvm_unreachable("Unhandled enum value");
 }

lib/Frontend/Frontend.cpp

@@ -581,7 +581,7 @@ void CompilerInstance::performSema() {
         finishTypeChecking(*SF);
 }
 
-void CompilerInstance::performParseOnly() {
+void CompilerInstance::performParseOnly(bool EvaluateConditionals) {
   const InputFileKind Kind = Invocation.getInputKind();
   ModuleDecl *MainModule = getMainModule();
   Context->LoadedModules[MainModule->getName()] = MainModule;
@@ -608,6 +608,7 @@ void CompilerInstance::performParseOnly() {
   }
 
   PersistentParserState PersistentState;
+  PersistentState.PerformConditionEvaluation = EvaluateConditionals;
   // Parse all the library files.
   for (auto BufferID : BufferIDs) {
     if (BufferID == MainBufferID)

lib/Parse/ParseIfConfig.cpp

@@ -36,6 +36,7 @@ Optional<PlatformConditionKind> getPlatformConditionKind(StringRef Name) {
     .Case("arch", PlatformConditionKind::Arch)
     .Case("_endian", PlatformConditionKind::Endianness)
     .Case("_runtime", PlatformConditionKind::Runtime)
+    .Case("canImport", PlatformConditionKind::CanImport)
     .Default(None);
 }
 
@@ -289,7 +290,7 @@ class ValidateIfConfigCondition :
       return E;
     }
 
-    // ( 'os' | 'arch' | '_endian' | '_runtime' ) '(' identifier ')''
+    // ( 'os' | 'arch' | '_endian' | '_runtime' | 'canImport') '(' identifier ')''
     auto Kind = getPlatformConditionKind(*KindName);
     if (!Kind.hasValue()) {
       D.diagnose(E->getLoc(), diag::unsupported_platform_condition_expression);
@@ -331,6 +332,8 @@ class ValidateIfConfigCondition :
         DiagName = "architecture"; break;
       case PlatformConditionKind::Endianness:
         DiagName = "endianness"; break;
+      case PlatformConditionKind::CanImport:
+        DiagName = "import conditional"; break;
       case PlatformConditionKind::Runtime:
         llvm_unreachable("handled above");
       }
@@ -450,6 +453,9 @@ class EvaluateIfConfigCondition :
           Str, SourceLoc(), nullptr).getValue();
       auto thisVersion = Ctx.LangOpts.EffectiveLanguageVersion;
       return thisVersion >= Val;
+    } else if (KindName == "canImport") {
+      auto Str = extractExprSource(Ctx.SourceMgr, Arg);
+      return Ctx.canImportModule({ Ctx.getIdentifier(Str) , E->getLoc()  });
     }
 
     auto Val = getDeclRefStr(Arg);
@@ -567,9 +573,10 @@ ParserResult<IfConfigDecl> Parser::parseIfConfig(
     Expr *Condition = nullptr;
     bool isActive = false;
 
-    // Parse and evaluate the directive.
+    // Parse the condition.  Evaluate it to determine the active
+    // clause unless we're doing a parse-only pass.
     if (isElse) {
-      isActive = !foundActive;
+      isActive = !foundActive && State->PerformConditionEvaluation;
     } else {
       llvm::SaveAndRestore<bool> S(InPoundIfEnvironment, true);
       ParserResult<Expr> Result = parseExprSequence(diag::expected_expr,
@@ -582,8 +589,9 @@ ParserResult<IfConfigDecl> Parser::parseIfConfig(
         // Error in the condition;
         isActive = false;
         isVersionCondition = false;
-      } else if (!foundActive) {
-        // Evaluate the condition only if we haven't found any active one.
+      } else if (!foundActive && State->PerformConditionEvaluation) {
+        // Evaluate the condition only if we haven't found any active one and
+        // we're not in parse-only mode.
         isActive = evaluateIfConfigCondition(Condition, Context);
         isVersionCondition = isVersionIfConfigCondition(Condition);
       }

test/ClangImporter/MixedSource/can_import_objc_idempotent.swift

@@ -13,7 +13,6 @@
 // RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk-nosource -I %t) -I %S/../Inputs/custom-modules -typecheck %s -verify
 
 // REQUIRES: objc_interop
-// REQUIRES: can_import
 
 // Test that 'canImport(Foo)' directives do not open symbols from 'Foo' into the
 // current module.  Only an 'import Foo' statement should do this.

test/ClangImporter/can_import_missing_requirement.swift

@@ -1,7 +1,6 @@
 // RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) -typecheck -I %S/Inputs/missing-requirement %s -verify
 
 // REQUIRES: objc_interop
-// REQUIRES: can_import
 
 class Unique {}
 

test/IDE/print_ast_non_typechecked.swift

@@ -23,5 +23,3 @@ func qux() {}
 // CHECK1: {{^}}  func qux() {
 // CHECK1: {{^}}  }
 // CHECK1: {{^}}#endif
-// CHECK1: {{^}}func qux() {
-// CHECK1: {{^}}}

test/Parse/ConditionalCompilation/can_import.swift

@@ -1,8 +1,6 @@
 // RUN: %target-typecheck-verify-swift -parse-as-library
 // RUN: %target-typecheck-verify-swift -D WITH_PERFORM -primary-file %s %S/Inputs/can_import_nonprimary_file.swift
 
-// REQUIRES: can_import
-
 public struct LibraryDependentBool : ExpressibleByBooleanLiteral {
 #if canImport(Swift)
   var _description: String

test/Parse/ConditionalCompilation/can_import_idempotent.swift

@@ -4,8 +4,6 @@
 // RUN: echo "public var dummyVar = Int()" | %target-swift-frontend -module-name DummyModule -emit-module -o %t -
 // RUN: %target-swift-frontend -typecheck -verify -I %t %s
 
-// REQUIRES: can_import
-
 #if canImport(DummyModule)
 print(DummyModule.dummyVar) // expected-error {{use of unresolved identifier 'DummyModule'}}
 print(dummyVar) // expected-error {{use of unresolved identifier 'dummyVar'}}

test/Parse/ConditionalCompilation/can_import_sdk.swift

@@ -1,7 +1,6 @@
 // RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) -typecheck -verify %s
 
 // REQUIRES: objc_interop
-// REQUIRES: can_import
 
 class Unique {} 
 

tools/SourceKit/lib/SwiftLang/SwiftDocSupport.cpp

@@ -1366,7 +1366,7 @@ SourceFile *SwiftLangSupport::getSyntacticSourceFile(
     Error = "Compiler invocation set up failed";
     return nullptr;
   }
-  ParseCI.performParseOnly();
+  ParseCI.performParseOnly(/*EvaluateConditionals*/true);
 
   SourceFile *SF = nullptr;
   unsigned BufferID = ParseCI.getInputBufferIDs().back();

tools/swift-refactor/swift-refactor.cpp

@@ -230,7 +230,7 @@ int main(int argc, char *argv[]) {
   switch (options::Action) {
     case RefactoringKind::GlobalRename:
     case RefactoringKind::FindGlobalRenameRanges:
-      CI.performParseOnly();
+      CI.performParseOnly(/*EvaluateConditionals*/true);
       break;
     default:
       CI.performSema();