fix #25573, add option to disable implicit dynamic

pkg/analyzer/lib/src/dart/element/type.dart

Index: pkg/analyzer/lib/src/dart/element/type.dart
diff --git a/pkg/analyzer/lib/src/dart/element/type.dart b/pkg/analyzer/lib/src/dart/element/type.dart
index 8d6aec0a5357e32d1dfde221bcc0d193a0b417d7..22a247ab3bfa0a509ded516f0a674157829c7ce6 100644
--- a/pkg/analyzer/lib/src/dart/element/type.dart
+++ b/pkg/analyzer/lib/src/dart/element/type.dart
@@ -927,6 +927,39 @@ class FunctionTypeImpl extends TypeImpl implements FunctionType {
   }
 
   /**
+   * Given a generic function type [g] and an instantiated function type [f],
+   * find a list of type arguments TArgs such that `g<TArgs> == f`,
+   * and return TArgs.
+   *
+   * This function must be called with type [f] that was instantiated from [g].
+   */
+  static Iterable<DartType> recoverTypeArguments(
+      FunctionType g, FunctionType f) {
+    // TODO(jmesserly): perhaps a better design here would be: instead of
+    // recording staticInvokeType on InvocationExpression, we could record the
+    // instantiated type arguments, that way we wouldn't need to recover them.
+    //
+    // For now though, this is a pretty quick operation.
+    assert(identical(g.element, f.element));
+    assert(g.typeFormals.isNotEmpty && f.typeFormals.isEmpty);
+    assert(g.typeFormals.length + g.typeArguments.length ==
+        f.typeArguments.length);
+
+    // Instantiation in Analyzer works like this:
+    // Given:
+    //     {U/T} <S> T -> S
+    // Where {U/T} represents the typeArguments (U) and typeParameters (T) list,
+    // and <S> represents the typeFormals.
+    //
+    // Now instantiate([V]), and the result should be:
+    //     {U/T, V/S} T -> S.
+    //
+    // Therefore, we can recover the typeArguments from our instantiated
+    // function.
+    return f.typeArguments.skip(g.typeArguments.length);
+  }
+
+  /**
    * Compares two function types [t] and [s] to see if their corresponding
    * parameter types match [parameterRelation] and their return types match
    * [returnRelation].