runtime: rename current_thread -> basic_scheduler (#1769)

It no longer supports executing !Send futures. The use case for
It is wanting a “light” runtime. There will be “local” task execution
using a different strategy coming later.

This patch also renames `thread_pool` -> `threaded_scheduler`, but
only in public APIs for now.

tokio/tests/process_issue_42.rs

@@ -18,7 +18,7 @@ fn run_test() {
     let finished_clone = finished.clone();
 
     thread::spawn(move || {
-        let mut rt = runtime::Builder::new().current_thread().build().unwrap();
+        let mut rt = runtime::Builder::new().basic_scheduler().build().unwrap();
 
         let mut futures = FuturesOrdered::new();
         rt.block_on(async {

tokio/tests/rt_basic.rs

@@ -28,7 +28,7 @@ fn spawned_task_does_not_progress_without_block_on() {
 
 fn rt() -> Runtime {
     tokio::runtime::Builder::new()
-        .current_thread()
+        .basic_scheduler()
         .build()
         .unwrap()
 }

tokio/tests/rt_common.rs

@@ -4,12 +4,12 @@
 
 macro_rules! rt_test {
     ($($t:tt)*) => {
-        mod current_thread {
+        mod basic_scheduler {
             $($t)*
 
             fn rt() -> Runtime {
                 tokio::runtime::Builder::new()
-                    .current_thread()
+                    .basic_scheduler()
                     .build()
                     .unwrap()
             }

tokio/tests/rt_threaded.rs

@@ -16,7 +16,10 @@ use std::task::{Context, Poll};
 #[test]
 fn single_thread() {
     // No panic when starting a runtime w/ a single thread
-    let _ = runtime::Builder::new().thread_pool().num_threads(1).build();
+    let _ = runtime::Builder::new()
+        .threaded_scheduler()
+        .num_threads(1)
+        .build();
 }
 
 #[test]
@@ -185,7 +188,7 @@ fn drop_threadpool_drops_futures() {
         let b = num_dec.clone();
 
         let rt = runtime::Builder::new()
-            .thread_pool()
+            .threaded_scheduler()
             .after_start(move || {
                 a.fetch_add(1, Relaxed);
             })
@@ -224,7 +227,7 @@ fn after_start_and_before_stop_is_called() {
     let after_inner = after_start.clone();
     let before_inner = before_stop.clone();
     let mut rt = tokio::runtime::Builder::new()
-        .thread_pool()
+        .threaded_scheduler()
         .after_start(move || {
             after_inner.clone().fetch_add(1, Ordering::Relaxed);
         })

tokio/tests/signal_drop_rt.rs

@@ -37,7 +37,7 @@ fn dropping_loops_does_not_cause_starvation() {
 
 fn rt() -> Runtime {
     tokio::runtime::Builder::new()
-        .current_thread()
+        .basic_scheduler()
         .build()
         .unwrap()
 }

tokio/tests/signal_multi_rt.rs

@@ -47,7 +47,7 @@ fn multi_loop() {
 
 fn rt() -> Runtime {
     tokio::runtime::Builder::new()
-        .current_thread()
+        .basic_scheduler()
         .build()
         .unwrap()
 }

tokio/tests/time_rt.rs

@@ -24,10 +24,10 @@ fn timer_with_threaded_runtime() {
 }
 
 #[test]
-fn timer_with_current_thread_runtime() {
+fn timer_with_basic_scheduler() {
     use tokio::runtime::Builder;
 
-    let mut rt = Builder::new().current_thread().build().unwrap();
+    let mut rt = Builder::new().basic_scheduler().build().unwrap();
     let (tx, rx) = mpsc::channel();
 
     rt.block_on(async move {