Fix System module export import = (microsoft#49788)

* Add more SystemJS test case

* Fix System module `export import =`

* Update test case

Author: magic-akari

src/compiler/transformers/module/system.ts

@@ -466,6 +466,20 @@ namespace ts {
                                     factory.createAssignment(importVariableName, parameterName)
                                 )
                             );
+                            if (hasSyntacticModifier(entry, ModifierFlags.Export)) {
+                                statements.push(
+                                    factory.createExpressionStatement(
+                                        factory.createCallExpression(
+                                            exportFunction,
+                                            /*typeArguments*/ undefined,
+                                            [
+                                                factory.createStringLiteral(idText(importVariableName)),
+                                                parameterName,
+                                            ]
+                                        )
+                                    )
+                                );
+                            }
                             break;
 
                         case SyntaxKind.ExportDeclaration:

tests/baselines/reference/systemModule18.js

@@ -0,0 +1,43 @@
+//// [tests/cases/compiler/systemModule18.ts] ////
+
+//// [react.ts]
+export function createElement() {}
+export function lazy() {}
+export function useState() {}
+
+//// [index.ts]
+export import React = require("./react.js");
+
+
+//// [react.js]
+System.register([], function (exports_1, context_1) {
+    "use strict";
+    var __moduleName = context_1 && context_1.id;
+    function createElement() { }
+    exports_1("createElement", createElement);
+    function lazy() { }
+    exports_1("lazy", lazy);
+    function useState() { }
+    exports_1("useState", useState);
+    return {
+        setters: [],
+        execute: function () {
+        }
+    };
+});
+//// [index.js]
+System.register(["./react.js"], function (exports_1, context_1) {
+    "use strict";
+    var React;
+    var __moduleName = context_1 && context_1.id;
+    return {
+        setters: [
+            function (React_1) {
+                React = React_1;
+                exports_1("React", React_1);
+            }
+        ],
+        execute: function () {
+        }
+    };
+});

tests/baselines/reference/systemModule18.symbols

@@ -0,0 +1,14 @@
+=== tests/cases/compiler/index.ts ===
+export import React = require("./react.js");
+>React : Symbol(React, Decl(index.ts, 0, 0))
+
+=== tests/cases/compiler/react.ts ===
+export function createElement() {}
+>createElement : Symbol(createElement, Decl(react.ts, 0, 0))
+
+export function lazy() {}
+>lazy : Symbol(lazy, Decl(react.ts, 0, 34))
+
+export function useState() {}
+>useState : Symbol(useState, Decl(react.ts, 1, 25))
+

tests/baselines/reference/systemModule18.types

@@ -0,0 +1,14 @@
+=== tests/cases/compiler/index.ts ===
+export import React = require("./react.js");
+>React : typeof React
+
+=== tests/cases/compiler/react.ts ===
+export function createElement() {}
+>createElement : () => void
+
+export function lazy() {}
+>lazy : () => void
+
+export function useState() {}
+>useState : () => void
+

tests/cases/compiler/systemModule18.ts

@@ -0,0 +1,9 @@
+// @module: system
+
+// @filename: react.ts
+export function createElement() {}
+export function lazy() {}
+export function useState() {}
+
+// @filename: index.ts
+export import React = require("./react.js");