Fix: new_thread spec helper must return isolated context (not thread) (#16421)

Tiny refactor to wait (join) on the isolated context, not its underlying thread.

Preparation for thread pool where isolated threads might not terminate immediately. We thus can't join the thread and must wait on the isolated context/fiber instead.

Author: ysbaddaden

spec/std/fiber/execution_context/global_queue_spec.cr

@@ -100,7 +100,7 @@ describe Fiber::ExecutionContext::GlobalQueue do
       queue = Fiber::ExecutionContext::GlobalQueue.new(Thread::Mutex.new)
       ready = Thread::WaitGroup.new(n)
 
-      threads = Array(Thread).new(n) do |i|
+      threads = Array.new(n) do |i|
         new_thread("ONE-#{i}") do
           slept = 0
           ready.done
@@ -147,7 +147,7 @@ describe Fiber::ExecutionContext::GlobalQueue do
         queue = Fiber::ExecutionContext::GlobalQueue.new(Thread::Mutex.new)
         ready = Thread::WaitGroup.new(n)
 
-        threads = Array(Thread).new(n) do |i|
+        threads = Array.new(n) do |i|
           new_thread("BULK-#{i}") do
             slept = 0
 

spec/std/fiber/execution_context/runnables_spec.cr

@@ -222,7 +222,7 @@ describe Fiber::ExecutionContext::Runnables do
         Fiber::ExecutionContext::Runnables(16).new(global_queue)
       end
 
-      threads = Array(Thread).new(n) do |i|
+      threads = Array.new(n) do |i|
         new_thread("RUN-#{i}") do
           runnables = all_runnables[i]
           slept = 0
@@ -277,7 +277,7 @@ describe Fiber::ExecutionContext::Runnables do
         Thread.sleep(10.nanoseconds) if i % 2 == 1
       end
 
-      threads.map(&.join)
+      threads.each(&.join)
 
       # must have dequeued each fiber exactly X times (no less, no more)
       fibers.each { |fc| fc.counter.should eq(increments) }

spec/support/thread.cr

@@ -1,8 +1,7 @@
 {% begin %}
-  def new_thread(name = nil, &block) : Thread
+  def new_thread(name = nil, &block)
     {% if flag?(:execution_context) %}
-      ctx = Fiber::ExecutionContext::Isolated.new(name: name || "SPEC") { block.call }
-      ctx.@thread
+      Fiber::ExecutionContext::Isolated.new(name: name || "SPEC") { block.call }
     {% else %}
       Thread.new(name) { block.call }
     {% end %}