Add structured coroutines and explicit error handling

internal/lang/coroutines_test.go

@@ -0,0 +1,69 @@
+package lang
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestGenerateStructuredCoroutines(t *testing.T) {
+	prog, err := Parse(`package demo
+suspend fun load(): Int { delay(1); return 42 }
+fun main() {
+    runBlocking {
+        coroutineScope {
+            launch { delay(1) }
+            val result = async<Int> { return load() }
+            println(result.await())
+        }
+    }
+}`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	out, err := GenerateGo(prog)
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, want := range []string{"func load(gotlinScope *GotlinCoroutineScope) int", "gotlinScope.Delay(1)", "gotlinScope.Launch", "gotlinAsync[int]", "load(gotlinScope)", ".await()", "gotlinRunBlocking"} {
+		if !strings.Contains(string(out), want) {
+			t.Fatalf("missing %q:\n%s", want, out)
+		}
+	}
+}
+
+func TestSuspendFunctionRequiresScope(t *testing.T) {
+	prog, err := Parse(`package demo
+suspend fun load(): Int { return 1 }
+fun main() { println(load()) }`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	_, err = GenerateGo(prog)
+	if err == nil || !strings.Contains(err.Error(), "requires a coroutine scope") {
+		t.Fatalf("unexpected error: %v", err)
+	}
+}
+
+func TestWorkerAndBareGoAreRemoved(t *testing.T) {
+	for _, source := range []string{`package demo worker Counter { var count = 0 }`, `package demo fun main() { go println("x") }`} {
+		if _, err := Parse(source); err == nil {
+			t.Fatalf("deprecated concurrency syntax parsed: %s", source)
+		}
+	}
+}
+
+func TestRunBlockingCancelsAndJoinsChildrenOnPanic(t *testing.T) {
+	prog, err := Parse(`package demo fun main() { runBlocking { launch { delay(1) }; panic("failed") } }`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	out, err := GenerateGo(prog)
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, want := range []string{"scope.cancel()", "scope.workers.Wait()", "panic(value)", "gotlinRunBlocking"} {
+		if !strings.Contains(string(out), want) {
+			t.Fatalf("missing %q:\n%s", want, out)
+		}
+	}
+}