Add ability to look up type parameters that are associated with ClassEntities with the element envi…

pkg/compiler/lib/src/kernel/element_map_impl.dart

Index: pkg/compiler/lib/src/kernel/element_map_impl.dart
diff --git a/pkg/compiler/lib/src/kernel/element_map_impl.dart b/pkg/compiler/lib/src/kernel/element_map_impl.dart
index a8ac5a068cd334aef4d022906f9140cbd3f6e837..d64b63256cc4edce4bf5a2f816f6d220bf9a870a 100644
--- a/pkg/compiler/lib/src/kernel/element_map_impl.dart
+++ b/pkg/compiler/lib/src/kernel/element_map_impl.dart
@@ -253,6 +253,11 @@ abstract class KernelToElementMapBase extends KernelToElementMapBaseMixin {
     }
   }
 
+  List<DartType> getTypeVariables(ir.Class cls) {
+    return cls.typeParameters
+        .map((ir.TypeParameter type) => getDartType(type.bound));

[Johnni Winther, 2017/09/04 06:59:56]

This is not the correct implementation.

class C<T extends String> {}

for this class [getTypeVariables] would return `[String]` and not `[T]`.

The correct implementation can be implementated directly in the element
environment (see comment below).

[Emily Fortuna, 2017/09/05 17:13:31]

Done.

+  }
+
   TypeVariableEntity getTypeVariable(ir.TypeParameter node) =>
       _getTypeVariable(node);
 
@@ -1274,6 +1279,16 @@ class KernelElementEnvironment implements ElementEnvironment {
     return elementMap._getFieldType(field);
   }
 
+  List<DartType> getTypeVariables(ClassEntity cls) {
+    ir.Class irClass = elementMap._classes.getEnv(cls).cls;
+    // Not all entities have corresponding ir.Nodes, but those that do not are
+    // synthetic elements like closure classes, which don't have specialized
+    // type variables.
+    return irClass == null
+        ? const <DartType>[]
+        : elementMap.getTypeVariables(irClass);

[Johnni Winther, 2017/09/04 06:59:56]

This method can be implemented using the current interface:

List<DartType> getTypeVariables(ClassEntity cls) =>
    getThisType(cls).typeArguments;

[Emily Fortuna, 2017/09/05 17:13:31]

Done.

+  }
+
   @override
   FunctionType getLocalFunctionType(covariant KLocalFunction function) {
     return function.functionType;