Make TyperState#test an inline method

Avoids the closure creation and megamorphic call.

Note: The method is probably too large to be inlined automatically by the JVM.

Author: odersky

compiler/src/dotty/tools/dotc/core/TyperState.scala

@@ -86,21 +86,23 @@ class TyperState(previous: TyperState /* | Null */) extends DotClass with Showab
   def uncommittedAncestor: TyperState =
     if (isCommitted) previous.uncommittedAncestor else this
 
-  private var testReporter: StoreReporter = null
+  private var myTestReporter: StoreReporter = null
+
+  def testReporter =
+    if (myTestReporter == null) new StoreReporter(reporter)
+    else {
+      myTestReporter.reset()
+      myTestReporter
+    }
 
   /** Test using `op`, restoring typerState to previous state afterwards */
-  def test(op: => Boolean): Boolean = {
+  @inline def test(op: => Boolean): Boolean = {
     val savedReporter = myReporter
     val savedConstraint = myConstraint
     val savedCommittable = myIsCommittable
     val savedCommitted = isCommitted
     myIsCommittable = false
-    myReporter =
-      if (testReporter == null) new StoreReporter(reporter)
-      else {
-        testReporter.reset()
-        testReporter
-      }
+    myReporter = testReporter
     try op
     finally {
       myReporter = savedReporter