Inject ambient context into Go calls

internal/lang/coroutines_test.go

@@ -116,6 +116,48 @@ fun main() { runBlocking { useContext() } }`)
 	}
 }
 
+func TestGoContextIsInjectedFromAmbientScope(t *testing.T) {
+	program, err := Parse(`package demo
+import exec os.exec
+fun command(): *exec.Cmd { return exec.commandContext("date") }
+fun main() { runBlocking { println(command()) } }`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	output, err := GenerateGo(program)
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, expected := range []string{"func command(gotlinScope *GotlinCoroutineScope) *exec.Cmd", `exec.CommandContext(gotlinScope.Context(), "date")`, "command(gotlinScope)"} {
+		if !strings.Contains(string(output), expected) {
+			t.Fatalf("missing %q:\n%s", expected, output)
+		}
+	}
+	call := program.Functions[0].Body[0].(ReturnStmt).Value.(CallExpr)
+	goCall, ok := call.Meta.Semantic.Node.(HIRGoCall)
+	if !ok || !goCall.InjectContext || !goCall.Variadic {
+		t.Fatalf("Go call context metadata = %#v", call.Meta.Semantic.Node)
+	}
+}
+
+func TestExplicitGoContextPreventsAmbientInjection(t *testing.T) {
+	program, err := Parse(`package demo
+import context
+import exec os.exec
+fun command(ctx: context.Context): *exec.Cmd { return exec.commandContext(ctx, "date") }`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	output, err := GenerateGo(program)
+	if err != nil {
+		t.Fatal(err)
+	}
+	code := string(output)
+	if strings.Contains(code, "func command(gotlinScope") || !strings.Contains(code, `exec.CommandContext(ctx, "date")`) {
+		t.Fatalf("explicit context was not preserved:\n%s", code)
+	}
+}
+
 func TestRunBlockingCancelsAndJoinsChildrenOnPanic(t *testing.T) {
 	prog, err := Parse(`package demo fun main() { runBlocking { launch { delay(1) }; panic("failed") } }`)
 	if err != nil {