Call method subtyping

Allow objects with an appropriately typed call method to subtype function types.  Fixes #19.

BUG=
[email protected]

Review URL: https://chromereviews.googleplex.com/140757013

Author: leafpetersen

bin/devc.dart

@@ -75,9 +75,9 @@ void main(List<String> argv) {
   var useColors = stdioType(stdout) == StdioType.TERMINAL;
   if (!args['dump-info']) setupLogger(level, print);
 
-  var typeResolver = new TypeResolver(shouldMockSdk ?
-      TypeResolver.sdkResolverFromMock(mockSdkSources) :
-      TypeResolver.sdkResolverFromDir(dartSdkPath));
+  var typeResolver = new TypeResolver(shouldMockSdk
+      ? TypeResolver.sdkResolverFromMock(mockSdkSources)
+      : TypeResolver.sdkResolverFromDir(dartSdkPath));
 
   var filename = args.rest.first;
   compile(filename, typeResolver,

bin/edit_files.dart

@@ -111,12 +111,12 @@ void main(List<String> argv) {
 
   Map json = JSON.decode(new File(filename).readAsStringSync());
   var summary = GlobalSummary.parse(json);
-  var excludePattern = (args['exclude-pattern'] != null) ?
-      new RegExp(args['exclude-pattern']) :
-      null;
-  var includePattern = (args['include-pattern'] != null) ?
-      new RegExp(args['include-pattern']) :
-      null;
+  var excludePattern = (args['exclude-pattern'] != null)
+      ? new RegExp(args['exclude-pattern'])
+      : null;
+  var includePattern = (args['include-pattern'] != null)
+      ? new RegExp(args['include-pattern'])
+      : null;
 
   var visitor = new EditFileSummaryVisitor(typeResolver, args['level'],
       args['checkout-files-executable'], args['checkout-files-arg'],

lib/devc.dart

@@ -60,10 +60,10 @@ Future<bool> compile(String inputFile, TypeResolver resolver,
 
   // Generate code.
   if (outputDir != null) {
-    var cg = outputDart ?
-        new DartGenerator(
-            outputDir, uri, results.libraries, results.rules, formatOutput) :
-        new JSGenerator(outputDir, uri, results.libraries, results.rules);
+    var cg = outputDart
+        ? new DartGenerator(
+            outputDir, uri, results.libraries, results.rules, formatOutput)
+        : new JSGenerator(outputDir, uri, results.libraries, results.rules);
     return cg.generate().then((_) => true);
   }
 

lib/src/checker/resolver.dart

@@ -34,9 +34,9 @@ class TypeResolver {
     var resolvers = [sdkResolver];
     if (otherResolvers == null) {
       resolvers.add(new FileUriResolver());
-      resolvers.add(_useMultipackage ?
-          new MultiPackageResolver() :
-          new PackageUriResolver([new JavaFile('packages/')]));
+      resolvers.add(_useMultipackage
+          ? new MultiPackageResolver()
+          : new PackageUriResolver([new JavaFile('packages/')]));
     } else {
       resolvers.addAll(otherResolvers);
     }

lib/src/checker/rules.dart

@@ -106,6 +106,16 @@ class RestrictedRules extends TypeRules {
     return true;
   }
 
+  FunctionType getCallMethodType(DartType t) {
+    if (t is InterfaceType) {
+      ClassElement element = t.element;
+      InheritanceManager manager = new InheritanceManager(element.library);
+      FunctionType callType = manager.lookupMemberType(t, "call");
+      return callType;
+    }
+    return null;
+  }
+
   /// Check that f1 is a subtype of f2. [ignoreReturn] is used in the DDC
   /// checker to determine whether f1 would be a subtype of f2 if the return
   /// type of f1 is set to match f2's return type.
@@ -249,12 +259,12 @@ class RestrictedRules extends TypeRules {
     if (t1 is! FunctionType && t2 is! FunctionType) return false;
 
     if (t1 is InterfaceType && t2 is FunctionType) {
-      // TODO(leafp): check t1 for a call method of the appropriate type
-      return false;
+      var callType = getCallMethodType(t1);
+      if (callType == null) return false;
+      return isFunctionSubTypeOf(callType, t2 as FunctionType);
     }
 
     if (t1 is FunctionType && t2 is InterfaceType) {
-      // TODO(leafp): check t2 for a call method of the appropriate type
       return false;
     }
 
@@ -376,6 +386,16 @@ class RestrictedRules extends TypeRules {
       return _wrapTo(fromT, toT);
     }
 
+    // For now, reject conversions between function types and
+    // call method objects.  We could choose to allow casts here.
+    // Wrapping a function type to assign it to a call method
+    // object will never succeed.  Wrapping the other way could
+    // be allowed.
+    if ((fromT is FunctionType && getCallMethodType(toT) != null) ||
+        (toT is FunctionType && getCallMethodType(fromT) != null)) {
+      return Coercion.error();
+    }
+
     // Downcast if toT <: fromT
     if (isSubTypeOf(toT, fromT)) return Coercion.cast(fromT, toT);
 

lib/src/codegen/js_codegen.dart

@@ -122,9 +122,9 @@ var _initializer = (function ($params) {
       List<String> initializedFields, bool needsInitializer) {
     var fieldParameters = ctor == null ? [] : getFieldFormalParameters(ctor);
 
-    var initializers = ctor == null ?
-        {} :
-        new Map.fromIterable(
+    var initializers = ctor == null
+        ? {}
+        : new Map.fromIterable(
             ctor.initializers.where((i) => i is ConstructorFieldInitializer),
             key: (i) => i.fieldName.name);
 
@@ -794,9 +794,9 @@ var $name = (function (_super) {
 
   String getLibraryId(LibraryElement element) {
     var libraryName = element.name;
-    return _builtins.containsKey(libraryName) ?
-        _builtins[libraryName] :
-        libraryName;
+    return _builtins.containsKey(libraryName)
+        ? _builtins[libraryName]
+        : libraryName;
   }
 
   void writeQualifiedName(Expression target, SimpleIdentifier id) {

lib/src/info.dart

@@ -167,7 +167,10 @@ abstract class DownCastBase extends Conversion {
       : super(rules, expression) {
     assert(_cast.toType != baseType &&
         _cast.fromType == baseType &&
-        (baseType.isDynamic || baseType.isAssignableTo(_cast.toType)));
+        (baseType.isDynamic ||
+            // Call methods make the following non-redundant
+            _cast.toType.isSubtypeOf(baseType) ||
+            baseType.isAssignableTo(_cast.toType)));
   }
 
   Cast get cast => _cast;
@@ -203,7 +206,9 @@ class DownCast extends DownCastBase {
     final toT = cast.toType;
 
     // toT <:_R fromT => to <: fromT
-    assert(toT.isAssignableTo(fromT));
+    // NB: classes with call methods are subtypes of function
+    // types, but the function type is not assignable to the class
+    assert(toT.isSubtypeOf(fromT) || fromT.isAssignableTo(toT));
 
     // Specialized casts:
     if (expression is Literal) {

lib/src/report.dart

@@ -485,8 +485,8 @@ class _Counter extends RecursiveSummaryVisitor {
 
 /// Returns a [SourceSpan] in [file] for the offsets of [node].
 SourceSpan _spanForNode(SourceFile file, AstNode node) {
-  final begin = node is AnnotatedNode ?
-      node.firstTokenAfterCommentAndMetadata.offset :
-      node.offset;
+  final begin = node is AnnotatedNode
+      ? node.firstTokenAfterCommentAndMetadata.offset
+      : node.offset;
   return file.span(begin, node.end);
 }

lib/src/testing.dart

@@ -47,9 +47,9 @@ CheckerResults testChecker(Map<String, String> testFiles, {bool mockSdk: true,
       reason: '`/main.dart` is missing in testFiles');
 
   // Create a resolver that can load test files from memory.
-  var dartUriResolver = mockSdk ?
-      TypeResolver.sdkResolverFromMock(mockSdkSources) :
-      TypeResolver.sdkResolverFromDir(dartSdkDirectory);
+  var dartUriResolver = mockSdk
+      ? TypeResolver.sdkResolverFromMock(mockSdkSources)
+      : TypeResolver.sdkResolverFromDir(dartSdkDirectory);
   var testUriResolver = new _TestUriResolver(testFiles);
   var resolver = new TypeResolver(dartUriResolver, [testUriResolver]);
 
@@ -288,9 +288,9 @@ class _TestSource implements Source {
   Uri resolveRelativeUri(Uri relativeUri) => uri.resolveUri(relativeUri);
 
   SourceSpan spanFor(AstNode node) {
-    final begin = node is AnnotatedNode ?
-        node.firstTokenAfterCommentAndMetadata.offset :
-        node.offset;
+    final begin = node is AnnotatedNode
+        ? node.firstTokenAfterCommentAndMetadata.offset
+        : node.offset;
     return _file.span(begin, node.end);
   }
 

test/checker/checker_test.dart

@@ -679,6 +679,71 @@ main() {
     });
   });
 
+  test('Function subtyping: objects with call methods', () {
+    testChecker({
+      '/main.dart': '''
+
+      typedef int I2I(int x);
+      typedef num N2N(num x);
+      class A {
+         int call(int x) => x;
+      }
+      class B {
+         num call(num x) => x;
+      }
+      int i2i(int x) => x;
+      num n2n(num x) => x;
+      void main() {
+         {
+           I2I f;
+           f = new A();
+           f = /*severe:StaticTypeError*/new B();
+           f = i2i;
+           f = /*warning:ClosureWrap*/n2n;
+           f = /*warning:DownCast*/(i2i as Object);
+           f = /*warning:DownCast*/(n2n as Function);
+         }
+         {
+           N2N f;
+           f = /*severe:StaticTypeError*/new A();
+           f = new B();
+           f = /*warning:ClosureWrap*/i2i;
+           f = n2n;
+           f = /*warning:DownCast*/(i2i as Object);
+           f = /*warning:DownCast*/(n2n as Function);
+         }
+         {
+           A f;
+           f = new A();
+           f = /*severe:StaticTypeError*/new B();
+           f = /*severe:StaticTypeError*/i2i;
+           f = /*severe:StaticTypeError*/n2n;
+           f = /*info:DownCast*/(i2i as Object);
+           f = /*info:DownCast*/(n2n as Function);
+         }
+         {
+           B f;
+           f = /*severe:StaticTypeError*/new A();
+           f = new B();
+           f = /*severe:StaticTypeError*/i2i;
+           f = /*severe:StaticTypeError*/n2n;
+           f = /*info:DownCast*/(i2i as Object);
+           f = /*info:DownCast*/(n2n as Function);
+         }
+         {
+           Function f;
+           f = new A();
+           f = new B();
+           f = i2i;
+           f = n2n;
+           f = /*info:DownCast*/(i2i as Object);
+           f = (n2n as Function);
+         }
+      }
+   '''
+    });
+  });
+
   test('Closure wrapping of literals', () {
     testChecker({
       '/main.dart': '''