Avoid expensive settings lookup in setDenot

Author: odersky

compiler/src/dotty/tools/dotc/Run.scala

@@ -231,6 +231,9 @@ class Run(comp: Compiler, ictx: Context) extends ImplicitRunInfo with Constraint
       ctx.settings.Yskip.value, ctx.settings.YstopBefore.value, stopAfter, ctx.settings.Ycheck.value)
     ctx.base.usePhases(phases)
 
+    if ctx.settings.YnoDoubleBindings.value then
+      ctx.base.checkNoDoubleBindings = true
+
     def runPhases(using Context) = {
       var lastPrintedTree: PrintedTree = NoPrintedTree
       val profiler = ctx.profiler

compiler/src/dotty/tools/dotc/config/Config.scala

@@ -83,13 +83,6 @@ object Config {
    */
   inline val failOnInstantiationToNothing = false
 
-  /** Enable noDoubleDef checking if option "-YnoDoubleDefs" is set.
-    * The reason to have an option as well as the present global switch is
-    * that the noDoubleDef checking is done in a hotspot, and we do not
-    * want to incur the overhead of checking an option each time.
-    */
-  inline val checkNoDoubleBindings = true
-
   /** Check positions for consistency after parsing */
   inline val checkPositions = true
 

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

@@ -986,6 +986,11 @@ object Contexts {
     /** Flag to suppress inlining, set after overflow */
     private[dotc] var stopInlining: Boolean = false
 
+    /** Cached -Yno-double-bindings setting. This is accessed from `setDenot`, which
+     *  is fairly hot, so we don't want to lookup the setting each time it is called.
+     */
+    private[dotc] var checkNoDoubleBindings = false
+
     /** A variable that records that some error was reported in a globally committable context.
      *  The error will not necessarlily be emitted, since it could still be that
      *  the enclosing context will be aborted. The variable is used as a smoke test

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

@@ -2440,9 +2440,8 @@ object Types {
       setDenot(memberDenot(name, allowPrivate = !symbol.exists || symbol.is(Private)))
 
     private def setDenot(denot: Denotation)(using Context): Unit = {
-      if (Config.checkNoDoubleBindings)
-        if (ctx.settings.YnoDoubleBindings.value)
-          checkSymAssign(denot.symbol)
+      if ctx.base.checkNoDoubleBindings then
+        checkSymAssign(denot.symbol)
 
       lastDenotation = denot
       lastSymbol = denot.symbol