Support top-level-await in TypeScript (#3024)

cli/tests/integration_tests.rs

@@ -567,3 +567,8 @@ itest!(top_level_await {
   args: "--allow-read top_level_await.js",
   output: "top_level_await.out",
 });
+
+itest!(top_level_await_ts {
+  args: "--allow-read top_level_await.ts",
+  output: "top_level_await.out",
+});

cli/tests/top_level_await.ts

@@ -0,0 +1,3 @@
+const buf: Uint8Array = await Deno.readFile("hello.txt");
+const n: number = await Deno.stdout.write(buf);
+console.log(`\n\nwrite ${n}`);

js/compiler.ts

@@ -539,6 +539,9 @@ window.compilerMain = function compilerMain(): void {
 
       diagnostics = ts.getPreEmitDiagnostics(program).filter(
         ({ code }): boolean => {
+          // TS1308: 'await' expression is only allowed within an async
+          // function.
+          if (code === 1308) return false;
           // TS2691: An import path cannot end with a '.ts' extension. Consider
           // importing 'bad-module' instead.
           if (code === 2691) return false;