Set new lazy vals impl as default

Author: szymon-rd

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

@@ -365,6 +365,7 @@ private sealed trait YSettings:
   val YshowTreeIds: Setting[Boolean] = BooleanSetting("-Yshow-tree-ids", "Uniquely tag all tree nodes in debugging output.")
   val YfromTastyIgnoreList: Setting[List[String]] = MultiStringSetting("-Yfrom-tasty-ignore-list", "file", "List of `tasty` files in jar files that will not be loaded when using -from-tasty")
   val YnoExperimental: Setting[Boolean] = BooleanSetting("-Yno-experimental", "Disable experimental language features")
+  val YlegacyLazyVals: Setting[Boolean] = BooleanSetting("-Ylegacy-lazy-vals", "Use legacy (pre 3.3.0) implementation of lazy vals")
 
   val YprofileEnabled: Setting[Boolean] = BooleanSetting("-Yprofile-enabled", "Enable profiling.")
   val YprofileDestination: Setting[String] = StringSetting("-Yprofile-destination", "file", "Where to send profiling output - specify a file, default is to the console.", "")
@@ -382,7 +383,6 @@ private sealed trait YSettings:
   val YrecheckTest: Setting[Boolean] = BooleanSetting("-Yrecheck-test", "Run basic rechecking (internal test only)")
   val YccDebug: Setting[Boolean] = BooleanSetting("-Ycc-debug", "Used in conjunction with captureChecking language import, debug info for captured references")
   val YccNoAbbrev: Setting[Boolean] = BooleanSetting("-Ycc-no-abbrev", "Used in conjunction with captureChecking language import, suppress type abbreviations")
-  val YlightweightLazyVals: Setting[Boolean] = BooleanSetting("-Ylightweight-lazy-vals", "Use experimental lightweight implementation of lazy vals")
 
   /** Area-specific debug output */
   val YexplainLowlevel: Setting[Boolean] = BooleanSetting("-Yexplain-lowlevel", "When explaining type errors, show types at a lower level.")

compiler/src/dotty/tools/dotc/transform/LazyVals.scala

@@ -448,10 +448,10 @@ class LazyVals extends MiniPhase with IdentityDenotTransformer {
 
   def transformMemberDefThreadSafe(x: ValOrDefDef)(using Context): Thicket = {
     assert(!(x.symbol is Mutable))
-    if ctx.settings.YlightweightLazyVals.value then
-      transformMemberDefThreadSafeNew(x)
-    else
+    if ctx.settings.YlegacyLazyVals.value then
       transformMemberDefThreadSafeLegacy(x)
+    else
+      transformMemberDefThreadSafeNew(x)
   }
 
   def transformMemberDefThreadSafeNew(x: ValOrDefDef)(using Context): Thicket = {

compiler/test/dotty/tools/dotc/CompilationTests.scala

@@ -45,7 +45,7 @@ class CompilationTests {
       compileFilesInDir("tests/pos-custom-args/erased", defaultOptions.and("-language:experimental.erasedDefinitions")),
       compileFilesInDir("tests/pos", defaultOptions.and("-Ysafe-init")),
       // Run tests for experimental lightweight lazy vals
-      compileFilesInDir("tests/pos", defaultOptions.and("-Ysafe-init", "-Ylightweight-lazy-vals", "-Ycheck-constraint-deps"), FileFilter.include(TestSources.posLazyValsAllowlist)),
+      compileFilesInDir("tests/pos", defaultOptions.and("-Ysafe-init", "-Ylegacy-lazy-vals", "-Ycheck-constraint-deps"), FileFilter.include(TestSources.posLazyValsAllowlist)),
       compileFilesInDir("tests/pos-deep-subtype", allowDeepSubtypes),
       compileFilesInDir("tests/pos-custom-args/no-experimental", defaultOptions.and("-Yno-experimental")),
       compileDir("tests/pos-special/java-param-names", defaultOptions.withJavacOnlyOptions("-parameters")),
@@ -214,7 +214,7 @@ class CompilationTests {
       compileFilesInDir("tests/run-deep-subtype", allowDeepSubtypes),
       compileFilesInDir("tests/run", defaultOptions.and("-Ysafe-init"), FileFilter.exclude("serialization-new.scala")),
       // Run tests for experimental lightweight lazy vals and stable lazy vals.
-      compileFilesInDir("tests/run", defaultOptions.and("-Ysafe-init", "-Ylightweight-lazy-vals", "-Ycheck-constraint-deps"), FileFilter.include(TestSources.runLazyValsAllowlist)),
+      compileFilesInDir("tests/run", defaultOptions.and("-Ysafe-init", "-Ylegacy-lazy-vals", "-Ycheck-constraint-deps"), FileFilter.include(TestSources.runLazyValsAllowlist)),
     ).checkRuns()
   }
 

tests/printing/transformed/lazy-vals-legacy.flags

@@ -0,0 +1 @@
+-Ylegacy-lazy-vals