Fix shadowing variable

Author: eregon

core/tracepoint/inspect_spec.rb

@@ -64,13 +64,12 @@ def trace_point_spec_test_return
 
   it 'returns a String showing the event, method, path and line for a :c_call event' do
     inspect = nil
-    line = nil
-    tp = TracePoint.new(:c_call) { |tp|
+    tracepoint = TracePoint.new(:c_call) { |tp|
       next unless TracePointSpec.target_thread?
       inspect ||= tp.inspect
     }
     line = __LINE__ + 2
-    tp.enable do
+    tracepoint.enable do
       [0, 1].max
     end