[flow] Add tests to assert the current typing behavior for the ref pr…

…op in component type

Summary:
Right now, it will produce good errors during subtyping, but has weird behavior in implicit instantiation.

I want to fix it, but let's first assert the current behavior, so we can easily see the improvement later.

Changelog: [internal]

Reviewed By: panagosg7

Differential Revision: D63154627

fbshipit-source-id: 7f4535592159d1f9a35e79c69eeb2693db6c35a1

tests/component_type/.flowconfig

@@ -0,0 +1,4 @@
+[options]
+component_syntax=true
+all=true
+no_flowlib=false

tests/component_type/abstract_component_to_component_type.js

@@ -0,0 +1,15 @@
+declare const Foo: React.AbstractComponent<{+bar: string}, Instance>;
+declare class Instance {}
+declare class ImNotARefSetter {}
+
+Foo as component(bar: string, ref: React.RefSetter<Instance>); // ok
+Foo as component(bar: number, ref: React.RefSetter<Instance>); // error: number ~> string
+Foo as component(ref: React.RefSetter<Instance>, ...{bar: number}); // error: number ~> string
+Foo as component( // error: Instance ~> string
+    bar: string,
+    ref: React.RefSetter<string>
+);
+Foo as component(
+    bar: string,
+    ref: ImNotARefSetter // error: bad ref
+);

tests/component_type/class_to_component_type.js

@@ -0,0 +1,14 @@
+declare class Foo extends React$Component<{bar: string}> {}
+declare class ImNotARefSetter {}
+
+Foo as component(bar: string, ref: React.RefSetter<Foo>); // ok
+Foo as component(bar: number, ref: React.RefSetter<Foo>); // error: number ~> string
+Foo as component(ref: React.RefSetter<Foo>, ...{bar: number}); // error: number ~> string
+Foo as component( // error: Foo ~> string
+    bar: string,
+    ref: React.RefSetter<string>
+);
+Foo as component(
+    bar: string,
+    ref: ImNotARefSetter // error: bad ref
+);