Merge pull request #15268 from dotty-staging/mb/revert-compiletime-op…

…s-covariance

Revert #14452 and make compile-time operations on stable arguments stable

bench-micro/src/main/scala/dotty/tools/benchmarks/TypeOpsBenchmark.scala

@@ -0,0 +1,56 @@
+package dotty.tools.benchmarks
+
+import org.openjdk.jmh.annotations.*
+import java.util.concurrent.TimeUnit.SECONDS
+import dotty.tools.dotc.{Driver, Run, Compiler}
+import dotty.tools.dotc.core.Mode
+import dotty.tools.dotc.core.Types.{TermRef, Type}
+import dotty.tools.dotc.core.Contexts.{ContextBase, Context, ctx, withMode}
+
+@Fork(value = 5)
+@Warmup(iterations = 5, time = 1, timeUnit = SECONDS)
+@Measurement(iterations = 5, time = 1, timeUnit = SECONDS)
+@State(Scope.Thread)
+class TypeOpsBenchmark:
+  var tp: Type = null
+  var context: Context = null
+
+  @Param(Array("int", "singletonsSum", "intsSum", "deepSingletonsSum", "deepIntsSum", "singletonsIntersection", "singletonsUnion"))
+  var valName: String = "int"
+
+  @Setup(Level.Iteration)
+  def setup(): Unit =
+    val driver = new Driver:
+      override def finish(compiler: Compiler, run: Run)(using Context): Unit =
+        withMode(Mode.Printing) {
+          val pkg = run.units(0).tpdTree.symbol
+          tp = pkg.requiredClass("Test").requiredValueRef(valName).underlying
+          context = ctx
+        }
+        super.finish(compiler, run)
+    driver.process(Array(
+      "-classpath", System.getProperty("BENCH_CLASS_PATH"),
+      "-Ystop-after:typer",
+      "tests/someTypes.scala"
+    ))
+
+  @Benchmark
+  def isStable(): Unit = tp.isStable(using context)
+
+  @Benchmark
+  def normalized(): Unit = tp.normalized(using context)
+
+  @Benchmark
+  def simplified(): Unit = tp.simplified(using context)
+
+  @Benchmark
+  def dealias(): Unit = tp.dealias(using context)
+
+  @Benchmark
+  def widen(): Unit = tp.widen(using context)
+
+  @Benchmark
+  def atoms(): Unit = tp.atoms(using context)
+
+  @Benchmark
+  def isProvisional(): Unit = tp.isProvisional(using context)

bench-micro/tests/someTypes.scala

@@ -0,0 +1,22 @@
+import compiletime.ops.int.+
+
+class Test:
+    val int: Int = 5
+
+    val int2: Int = 6
+
+    val singletonsSum: int.type + int2.type = ???
+
+    val intsSum: Int + Int = ???
+
+    val deepSingletonsSum:
+        ((int.type + int2.type) + (int.type + int2.type)) + ((int.type + int2.type) + (int.type + int2.type)) +
+        ((int.type + int2.type) + (int.type + int2.type)) + ((int.type + int2.type) + (int.type + int2.type)) = ???
+
+    val deepIntsSum:
+        ((Int + Int) + (Int + Int)) + ((Int + Int) + (Int + Int)) +
+        ((Int + Int) + (Int + Int)) + ((Int + Int) + (Int + Int)) = ???
+
+    val singletonsIntersection: int.type & int2.type = ???
+
+    val singletonsUnion: int.type | int2.type = ???

build.sbt

@@ -13,6 +13,7 @@ val `scala3-tasty-inspector` = Build.`scala3-tasty-inspector`
 val `scala3-language-server` = Build.`scala3-language-server`
 val `scala3-bench` = Build.`scala3-bench`
 val `scala3-bench-bootstrapped` = Build.`scala3-bench-bootstrapped`
+val `scala3-bench-micro` = Build.`scala3-bench-micro`
 val `stdlib-bootstrapped` = Build.`stdlib-bootstrapped`
 val `stdlib-bootstrapped-tasty-tests` = Build.`stdlib-bootstrapped-tasty-tests`
 val `tasty-core` = Build.`tasty-core`

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

@@ -175,6 +175,7 @@ object Types {
         // see: tests/explicit-nulls/pos/flow-stable.scala.disabled
         tp.tp1.isStable && (realizability(tp.tp2) eq Realizable) ||
         tp.tp2.isStable && (realizability(tp.tp1) eq Realizable)
+      case tp: AppliedType => tp.cachedIsStable
       case _ => false
     }
 
@@ -4162,10 +4163,32 @@ object Types {
     private var myStableHash: Byte = 0
     private var myGround: Byte = 0
 
+    private var myIsStablePeriod: Period = Nowhere
+    private var myIsStable: Boolean = false
+
     def isGround(acc: TypeAccumulator[Boolean])(using Context): Boolean =
       if myGround == 0 then myGround = if acc.foldOver(true, this) then 1 else -1
       myGround > 0
 
+    private[Types] def cachedIsStable(using Context): Boolean =
+      // We need to invalidate the cache when the period changes because the
+      // case `TermRef` of `Type#isStable` reads denotations, which depend on
+      // the period. See docs/_docs/internals/periods.md for more information.
+      if myIsStablePeriod != ctx.period then
+        val res: Boolean = computeIsStable
+        // We don't cache if the type is provisional because `Type#isStable`
+        // calls `Type#stripTypeVar` which might return different results later.
+        if !isProvisional then
+          myIsStablePeriod = ctx.period
+          myIsStable = res
+        res
+      else
+        myIsStable
+
+    private def computeIsStable(using Context): Boolean = tycon match
+      case tycon: TypeRef if defn.isCompiletimeAppliedType(tycon.symbol) && args.forall(_.isStable) => true
+      case _ => false
+
     override def underlying(using Context): Type = tycon
 
     override def superType(using Context): Type =
@@ -4243,7 +4266,7 @@ object Types {
             // final val one = 1
             // type Two = one.type + one.type
             // ```
-            case tp: TermRef => tp.underlying
+            case tp: TypeProxy if tp.underlying.isStable => tp.underlying.fixForEvaluation
             case tp => tp
           }
 

compiler/src/dotty/tools/dotc/plugins/Plugins.scala

@@ -51,7 +51,7 @@ trait Plugins {
     }
     else _roughPluginsList
 
-  /** Load all available plugins.  Skips plugins that
+  /** Load all available plugins. Skips plugins that
    *  either have the same name as another one, or which
    *  define a phase name that another one does.
    */

library/src/scala/compiletime/ops/any.scala

@@ -13,7 +13,7 @@ object any:
    * ```
    * @syntax markdown
    */
-  type ==[+X, +Y] <: Boolean
+  type ==[X, Y] <: Boolean
 
   /** Inequality comparison of two singleton types.
    * ```scala
@@ -26,7 +26,7 @@ object any:
    * ```
    * @syntax markdown
    */
-  type !=[+X, +Y] <: Boolean
+  type !=[X, Y] <: Boolean
 
   /** Tests if a type is a constant.
    * ```scala
@@ -63,4 +63,4 @@ object any:
    *  ```
    *  @syntax markdown
    */
-  type ToString[+X] <: String
+  type ToString[X] <: String

library/src/scala/compiletime/ops/boolean.scala

@@ -13,7 +13,7 @@ object boolean:
    *  ```
    *  @syntax markdown
    */
-  type ![+X <: Boolean] <: Boolean
+  type ![X <: Boolean] <: Boolean
 
   /** Exclusive disjunction of two `Boolean` singleton types.
    *  ```scala
@@ -25,7 +25,7 @@ object boolean:
    *  ```
    *  @syntax markdown
    */
-  type ^[+X <: Boolean, +Y <: Boolean] <: Boolean
+  type ^[X <: Boolean, Y <: Boolean] <: Boolean
 
   /** Conjunction of two `Boolean` singleton types.
    *  ```scala
@@ -37,7 +37,7 @@ object boolean:
    *  ```
    *  @syntax markdown
    */
-  type &&[+X <: Boolean, +Y <: Boolean] <: Boolean
+  type &&[X <: Boolean, Y <: Boolean] <: Boolean
 
   /** Disjunction of two `Boolean` singleton types.
    *  ```scala
@@ -49,4 +49,4 @@ object boolean:
    *  ```
    *  @syntax markdown
    */
-  type ||[+X <: Boolean, +Y <: Boolean] <: Boolean
+  type ||[X <: Boolean, Y <: Boolean] <: Boolean

library/src/scala/compiletime/ops/double.scala

@@ -11,7 +11,7 @@ object double:
    *  ```
    *  @syntax markdown
    */
-  type +[+X <: Double, +Y <: Double] <: Double
+  type +[X <: Double, Y <: Double] <: Double
 
   /** Subtraction of two `Double` singleton types.
    *  ```scala
@@ -22,7 +22,7 @@ object double:
    *  ```
    *  @syntax markdown
    */
-  type -[+X <: Double, +Y <: Double] <: Double
+  type -[X <: Double, Y <: Double] <: Double
 
   /** Multiplication of two `Double` singleton types.
    *  ```scala
@@ -33,7 +33,7 @@ object double:
    *  ```
    *  @syntax markdown
    */
-  type *[+X <: Double, +Y <: Double] <: Double
+  type *[X <: Double, Y <: Double] <: Double
 
   /** Integer division of two `Double` singleton types.
    *  ```scala
@@ -44,7 +44,7 @@ object double:
    *  ```
    *  @syntax markdown
    */
-  type /[+X <: Double, +Y <: Double] <: Double
+  type /[X <: Double, Y <: Double] <: Double
 
   /** Remainder of the division of `X` by `Y`.
    *  ```scala
@@ -55,7 +55,7 @@ object double:
    *  ```
    *  @syntax markdown
    */
-  type %[+X <: Double, +Y <: Double] <: Double
+  type %[X <: Double, Y <: Double] <: Double
 
   /** Less-than comparison of two `Double` singleton types.
    *  ```scala
@@ -67,7 +67,7 @@ object double:
    *  ```
    *  @syntax markdown
    */
-  type <[+X <: Double, +Y <: Double] <: Boolean
+  type <[X <: Double, Y <: Double] <: Boolean
 
   /** Greater-than comparison of two `Double` singleton types.
    *  ```scala
@@ -79,7 +79,7 @@ object double:
    *  ```
    *  @syntax markdown
    */
-  type >[+X <: Double, +Y <: Double] <: Boolean
+  type >[X <: Double, Y <: Double] <: Boolean
 
   /** Greater-or-equal comparison of two `Double` singleton types.
    *  ```scala
@@ -91,7 +91,7 @@ object double:
    *  ```
    *  @syntax markdown
    */
-  type >=[+X <: Double, +Y <: Double] <: Boolean
+  type >=[X <: Double, Y <: Double] <: Boolean
 
   /** Less-or-equal comparison of two `Double` singleton types.
    *  ```scala
@@ -103,7 +103,7 @@ object double:
    *  ```
    *  @syntax markdown
    */
-  type <=[+X <: Double, +Y <: Double] <: Boolean
+  type <=[X <: Double, Y <: Double] <: Boolean
 
   /** Absolute value of an `Double` singleton type.
    *  ```scala
@@ -114,7 +114,7 @@ object double:
    *  ```
    *  @syntax markdown
    */
-  type Abs[+X <: Double] <: Double
+  type Abs[X <: Double] <: Double
 
   /** Negation of an `Double` singleton type.
    *  ```scala
@@ -126,7 +126,7 @@ object double:
    *  ```
    *  @syntax markdown
    */
-  type Negate[+X <: Double] <: Double
+  type Negate[X <: Double] <: Double
 
   /** Minimum of two `Double` singleton types.
    *  ```scala
@@ -137,7 +137,7 @@ object double:
    *  ```
    *  @syntax markdown
    */
-  type Min[+X <: Double, +Y <: Double] <: Double
+  type Min[X <: Double, Y <: Double] <: Double
 
   /** Maximum of two `Double` singleton types.
    *  ```scala
@@ -148,7 +148,7 @@ object double:
    *  ```
    *  @syntax markdown
    */
-  type Max[+X <: Double, +Y <: Double] <: Double
+  type Max[X <: Double, Y <: Double] <: Double
 
   /** Int conversion of a `Double` singleton type.
    *  ```scala
@@ -159,7 +159,7 @@ object double:
    *  ```
    *  @syntax markdown
    */
-  type ToInt[+X <: Double] <: Int
+  type ToInt[X <: Double] <: Int
 
   /** Long conversion of a `Double` singleton type.
    *  ```scala
@@ -170,7 +170,7 @@ object double:
    *  ```
    *  @syntax markdown
    */
-  type ToLong[+X <: Double] <: Long
+  type ToLong[X <: Double] <: Long
 
   /** Float conversion of a `Double` singleton type.
    *  ```scala
@@ -181,4 +181,4 @@ object double:
    *  ```
    *  @syntax markdown
    */
-  type ToFloat[+X <: Double] <: Float
+  type ToFloat[X <: Double] <: Float