Increase test coverage (#4742)

* Add tests for path type inferers

* Add test for babel-types.valueToNode

* Add tests for babel-types.toKeyAlias

* Add tests for babel-types.toStatement

* Add tests for babel-types.toExpression

* Lint fixes in babel-traverse/test/inference

packages/babel-traverse/src/path/inference/inferers.js

@@ -137,7 +137,13 @@ function Func() {
   return t.genericTypeAnnotation(t.identifier("Function"));
 }
 
-export { Func as Function, Func as Class };
+export {
+  Func as FunctionExpression,
+  Func as ArrowFunctionExpression,
+  Func as FunctionDeclaration,
+  Func as ClassExpression,
+  Func as ClassDeclaration
+};
 
 export function CallExpression() {
   return resolveCall(this.get("callee"));