Fix behavior when typed JS interop getters are called as functions.

pkg/compiler/lib/src/js_emitter/program_builder/program_builder.dart

Index: pkg/compiler/lib/src/js_emitter/program_builder/program_builder.dart
diff --git a/pkg/compiler/lib/src/js_emitter/program_builder/program_builder.dart b/pkg/compiler/lib/src/js_emitter/program_builder/program_builder.dart
index 5f5543926f33ac58d5bc4687c708fa304cfcba9e..4560a8c7d7117a54dced15e847afd3cc888223b4 100644
--- a/pkg/compiler/lib/src/js_emitter/program_builder/program_builder.dart
+++ b/pkg/compiler/lib/src/js_emitter/program_builder/program_builder.dart
@@ -30,7 +30,9 @@ import '../../constants/values.dart' show
 import '../../core_types.dart' show
     CoreClasses;
 import '../../dart_types.dart' show
-    DartType;
+    DartType,
+    FunctionType,
+    TypedefType;
 import '../../elements/elements.dart' show
     ClassElement,
     Element,
@@ -38,6 +40,7 @@ import '../../elements/elements.dart' show
     FieldElement,
     FunctionElement,
     FunctionSignature,
+    GetterElement,
     LibraryElement,
     MethodElement,
     Name,
@@ -407,7 +410,41 @@ class ProgramBuilder {
               }
             }
 
+            bool isFunctionLike = false;

[sra1, 2015/10/30 20:54:59]

Explain (comment) that this is generating stubs for direct calls and stubs for
call-through. 

[Jacob, 2015/10/30 22:31:53]

Done.

+            FunctionType functionType;

[sra1, 2015/10/30 20:54:59]

I like to add = null if it is not set one some path.

[Jacob, 2015/10/30 22:31:53]

Done.

+
             if (member.isFunction) {
+              FunctionElement fn = member;
+              functionType = fn.type;
+            } else if (member.isGetter) {
+              GetterElement getter = member;
+              DartType returnType = getter.type.returnType;
+              if (returnType.isFunctionType) {
+                functionType = returnType;
+              } else if (_compiler.types.isSubtype(returnType,
+                      backend.coreTypes.functionType) ||
+                  returnType.treatAsDynamic) {

[sra1, 2015/10/30 20:54:59]

Horrible indentation.  If it is the formatter, can it be fixed by switching ||
operands?

[Jacob, 2015/10/30 22:31:53]

done. shame line length isn't 100.

+                if (returnType.isTypedef) {
+                  TypedefType typedef = returnType;
+                  functionType = typedef.element.functionSignature.type;
+                } else {
+                  // Other misc function type such as coreTypes.Function.
+                  // Allow any number of arguments.
+                  isFunctionLike = true;
+                }
+              }
+            } // TODO(jacobr): handle field elements.
+
+            if (isFunctionLike || functionType != null) {
+              int minArgs;
+              int maxArgs;
+              if (functionType != null) {
+                minArgs = functionType.parameterTypes.length;
+                maxArgs = minArgs + functionType.optionalParameterTypes.length;
+              } else {
+                minArgs = 0;
+                maxArgs = 32767;
+              }
               var selectors =
                   _compiler.codegenWorld.invocationsByName(member.name);
               FunctionElement fn = member;

[sra1, 2015/10/30 20:54:59]

'fn' unused below.  Will fail if you TODO handle field elements

[Jacob, 2015/10/30 22:31:53]

done. forgot to remove this.

@@ -418,15 +455,14 @@ class ProgramBuilder {
                 for (var selector in selectors.keys) {
                   // Check whether the arity matches this member.
                   var argumentCount = selector.argumentCount;
-                  if (argumentCount > fn.parameters.length) break;
-                  if (argumentCount < fn.parameters.length &&
-                      !fn.parameters[argumentCount].isOptional) break;
+                  // JS interop does not support named arguments.
+                  if (selector.namedArgumentCount > 0) break;
+                  if (argumentCount < minArgs) break;
+                  if (argumentCount > maxArgs) break;
                   var stubName = namer.invocationName(selector);
                   if (!stubNames.add(stubName.key)) break;
-                  var candidateParameterNames =
-                      'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLOMOPQRSTUVWXYZ';
                   var parameters = new List<String>.generate(argumentCount,
-                      (i) => candidateParameterNames[i]);
+                      (i) => 'p$i');

[Siggi Cherem (dart-lang), 2015/10/30 19:54:17]

you could also keep the old naming scheme to optimize for functions with few
arguments. For example:

var candidateNames = 'abc....';
(i) => i < 52 ? candidateNames[i] : '${candidateNames[i % 52]}${i ~/ 52}'

[Jacob, 2015/10/30 22:31:53]

not needed. these names will be minified anyway so the previous code was a
premature optimization.

 
                   interceptorClass.callStubs.add(_buildStubMethod(
                       stubName,

[sra1, 2015/10/30 20:54:59]

Do you get duplicate stubs?

[Jacob, 2015/10/30 22:31:53]

no because of 
if (!stubNames.add(stubName.key)) break

siggi complained about my deep nesting so it is written this way which makes it
a little harder to spot this line.