Re-remove ad hoc Future.then inference.

pkg/analyzer/lib/src/generated/static_type_analyzer.dart

Index: pkg/analyzer/lib/src/generated/static_type_analyzer.dart
diff --git a/pkg/analyzer/lib/src/generated/static_type_analyzer.dart b/pkg/analyzer/lib/src/generated/static_type_analyzer.dart
index 1c5b9996a579c52c77f2cc605950147e4ee57ab8..821ad430b963d55830dc69f5ddfd43612c478f6e 100644
--- a/pkg/analyzer/lib/src/generated/static_type_analyzer.dart
+++ b/pkg/analyzer/lib/src/generated/static_type_analyzer.dart
@@ -1948,46 +1948,6 @@ class StaticTypeAnalyzer extends SimpleAstVisitor<Object> {
           argTypes.add(argumentList.arguments[i].staticType);
         }
       }
-
-      // TODO(leafp): remove this again after code has been updated to
-      // use FutureOr on classes that implement Future
-      // Special case Future<T>.then upwards inference. It has signature:
-      //
-      //     <S>(T -> (S | Future<S>)) -> Future<S>
-      //
-      // Based on the first argument type, we'll pick one of these signatures:
-      //
-      //     <S>(T -> S) -> Future<S>
-      //     <S>(T -> Future<S>) -> Future<S>
-      //
-      // ... and finish the inference using that.
-      if (argTypes.isNotEmpty && _resolver.isFutureThen(fnType.element)) {
-        var firstArgType = argTypes[0];
-        var firstParamType = params[0].type;
-        if (firstArgType is FunctionType &&
-            firstParamType is FunctionType &&
-            !firstParamType.returnType.isDartAsyncFutureOr) {
-          var argReturnType = firstArgType.returnType;
-          // Skip the inference if we have the top type. It can only lead to
-          // worse inference. For example, this happens when the lambda returns
-          // S or Future<S> in a conditional.
-          if (!argReturnType.isObject && !argReturnType.isDynamic) {
-            DartType paramReturnType = _typeProvider.futureOrType
-                .instantiate([fnType.typeFormals[0].type]);
-
-            // Adjust the expected parameter type to have this return type.
-            var function = new FunctionElementImpl(firstParamType.name, -1)
-              ..isSynthetic = true
-              ..shareParameters(firstParamType.parameters.toList())
-              ..returnType = paramReturnType;
-            function.type = new FunctionTypeImpl(function);
-            // Use this as the expected 1st parameter type.
-            params[0] = new ParameterElementImpl.synthetic(
-                params[0].name, function.type, params[0].parameterKind);
-          }
-        }
-      }
-
       return ts.inferGenericFunctionOrType(
           fnType, params, argTypes, InferenceContext.getContext(node),
           errorReporter: _resolver.errorReporter, errorNode: errorNode);