Merge pull request #12560 from dotty-staging/improve-typeinf

smarter · web-flow · commit 17a6ab0635d3 · 2021-05-25T22:09:03.000+02:00
Harden Type Inference
diff --git a/compiler/src/dotty/tools/dotc/typer/Inferencing.scala b/compiler/src/dotty/tools/dotc/typer/Inferencing.scala
@@ -33,7 +33,10 @@ object Inferencing {
    */
   def isFullyDefined(tp: Type, force: ForceDegree.Value)(using Context): Boolean = {
     val nestedCtx = ctx.fresh.setNewTyperState()
-    val result = new IsFullyDefinedAccumulator(force)(using nestedCtx).process(tp)
+    val result =
+      try new IsFullyDefinedAccumulator(force)(using nestedCtx).process(tp)
+      catch case ex: StackOverflowError =>
+        false // can happen for programs with illegal recusions, e.g. neg/recursive-lower-constraint.scala
     if (result) nestedCtx.typerState.commit()
     result
   }
@@ -43,7 +46,7 @@ object Inferencing {
    */
   def canDefineFurther(tp: Type)(using Context): Boolean =
     val prevConstraint = ctx.typerState.constraint
-    isFullyDefined(tp, force = ForceDegree.all)
+    isFullyDefined(tp, force = ForceDegree.failBottom)
     && (ctx.typerState.constraint ne prevConstraint)
 
   /** The fully defined type, where all type variables are forced.
@@ -687,7 +690,7 @@ trait Inferencing { this: Typer =>
 
         val arg = findArg(call)
         if !arg.isEmpty then
-          var argType = arg.tpe
+          var argType = arg.tpe.widenExpr.widenTermRefExpr
           if !argType.isSingleton then argType = SkolemType(argType)
           argType <:< tvar
       case _ =>
diff --git a/compiler/src/dotty/tools/dotc/typer/ReTyper.scala b/compiler/src/dotty/tools/dotc/typer/ReTyper.scala
@@ -134,4 +134,5 @@ class ReTyper extends Typer with ReChecking {
   override protected def addAccessorDefs(cls: Symbol, body: List[Tree])(using Context): List[Tree] = body
   override protected def checkEqualityEvidence(tree: tpd.Tree, pt: Type)(using Context): Unit = ()
   override protected def matchingApply(methType: MethodOrPoly, pt: FunProto)(using Context): Boolean = true
+  override protected def typedScala2MacroBody(call: untpd.Tree)(using Context): Tree = promote(call)
 }
diff --git a/compiler/src/dotty/tools/dotc/typer/Typer.scala b/compiler/src/dotty/tools/dotc/typer/Typer.scala
@@ -3685,7 +3685,7 @@ class Typer extends Namer
           return readapt(tree.cast(target))
 
       def recover(failure: SearchFailureType) =
-        if canDefineFurther(wtp) then readapt(tree)
+        if canDefineFurther(wtp) || canDefineFurther(pt) then readapt(tree)
         else err.typeMismatch(tree, pt, failure)
 
       pt match
@@ -3907,7 +3907,7 @@ class Typer extends Namer
         report.warning(PureExpressionInStatementPosition(original, exprOwner), original.srcPos)
 
   /** Types the body Scala 2 macro declaration `def f = macro <body>` */
-  private def typedScala2MacroBody(call: untpd.Tree)(using Context): Tree =
+  protected def typedScala2MacroBody(call: untpd.Tree)(using Context): Tree =
     // TODO check that call is to a method with valid signature
     def typedPrefix(tree: untpd.RefTree)(splice: Context ?=> Tree => Tree)(using Context): Tree = {
       tryAlternatively {
diff --git a/tests/neg-scalajs/jsconstructortag-error-in-typer.check b/tests/neg-scalajs/jsconstructortag-error-in-typer.check
@@ -4,7 +4,7 @@
   |no implicit argument of type scala.scalajs.js.ConstructorTag[ScalaClass] was found for parameter tag of method constructorTag in package scala.scalajs.js.
   |I found:
   |
-  |    scala.scalajs.js.ConstructorTag.materialize[Nothing]
+  |    scala.scalajs.js.ConstructorTag.materialize[T]
   |
   |But method materialize in object ConstructorTag does not match type scala.scalajs.js.ConstructorTag[ScalaClass].
 -- Error: tests/neg-scalajs/jsconstructortag-error-in-typer.scala:10:39 ------------------------------------------------
@@ -13,7 +13,7 @@
    |no implicit argument of type scala.scalajs.js.ConstructorTag[ScalaTrait] was found for parameter tag of method constructorTag in package scala.scalajs.js.
    |I found:
    |
-   |    scala.scalajs.js.ConstructorTag.materialize[Nothing]
+   |    scala.scalajs.js.ConstructorTag.materialize[T]
    |
    |But method materialize in object ConstructorTag does not match type scala.scalajs.js.ConstructorTag[ScalaTrait].
 -- Error: tests/neg-scalajs/jsconstructortag-error-in-typer.scala:11:45 ------------------------------------------------
@@ -22,6 +22,6 @@
    |no implicit argument of type scala.scalajs.js.ConstructorTag[ScalaObject.type] was found for parameter tag of method constructorTag in package scala.scalajs.js.
    |I found:
    |
-   |    scala.scalajs.js.ConstructorTag.materialize[Nothing]
+   |    scala.scalajs.js.ConstructorTag.materialize[T]
    |
    |But method materialize in object ConstructorTag does not match type scala.scalajs.js.ConstructorTag[ScalaObject.type].
diff --git a/tests/neg/i4986a.check b/tests/neg/i4986a.check
@@ -4,6 +4,6 @@
   |Cannot construct a collection of type List[String] with elements of type Int based on a collection of type List[Int]..
   |I found:
   |
-  |    collection.BuildFrom.buildFromIterableOps[Nothing, Nothing, Nothing]
+  |    collection.BuildFrom.buildFromIterableOps[CC, A0, A]
   |
   |But method buildFromIterableOps in trait BuildFromLowPriority2 does not match type collection.BuildFrom[List[Int], Int, List[String]].
diff --git a/tests/neg/i7056.check b/tests/neg/i7056.check
diff --git a/tests/neg/i864.scala b/tests/neg/i864.scala
@@ -6,5 +6,5 @@ object C {
   trait X[T]
   implicit def u[A, B]: X[A | B] = new X[A | B] {}
   def y[T](implicit x: X[T]): T = ???
-  val x: a.type & b.type | b.type & c.type = y
+  val x: a.type & b.type | b.type & c.type = y // error
 }
diff --git a/tests/neg/typeclass-encoding3.scala b/tests/neg/typeclass-encoding3.scala
@@ -344,5 +344,6 @@ object functors {
       ??? // $this.flatMap[A](identity)   disabled since it does not typecheck
   }
 
-  MonadFlatten.flattened(List(List(1, 2, 3), List(4, 5)))
+  MonadFlatten.flattened(List(List(1, 2, 3), List(4, 5))) // ok, synthesizes (using ListMonad)
+  MonadFlatten.flattened(List(List(1, 2, 3), List(4, 5)))(using ListMonad) // error
 }
diff --git a/tests/pos/depfun.scala b/tests/pos/depfun.scala
@@ -0,0 +1,17 @@
+// The following test is derived from scala/reflect/TypeTest.scala, but using
+// a dependent function instead of a dependent SAM. It shows that the special treatment
+// using a DependentTypeTree is not needed for plain function types.
+// But for SAM types, the treatment is needed, otherwise TypeTest.scala does
+// not typecheck. Todo: Figure out the reason for this difference.
+object Test:
+
+  type F[S, T] = (x: S) => Option[x.type & T]
+
+  /** Trivial type test that always succeeds */
+  def identity[T]: F[T, T] = Some(_)
+
+  val x: 1 = 1
+  val y = identity(x)
+  val z: Option[1] = y
+
+
diff --git a/tests/pos/i7056.scala b/tests/pos/i7056.scala
@@ -16,4 +16,5 @@ given [T <: A](using PartialId[T]): T1[T] = new T1[T] {
 given PartialId[B] = ???
 
 val x: B = ???
-val z = x.idnt1  // error
+val z = x.idnt1  // used to be an error, now ok
+

Original file line number	Diff line number	Diff line change
`@@ -134,4 +134,5 @@ class ReTyper extends Typer with ReChecking {`
`134`	`134`	`override protected def addAccessorDefs(cls: Symbol, body: List[Tree])(using Context): List[Tree] = body`
`135`	`135`	`override protected def checkEqualityEvidence(tree: tpd.Tree, pt: Type)(using Context): Unit = ()`
`136`	`136`	`override protected def matchingApply(methType: MethodOrPoly, pt: FunProto)(using Context): Boolean = true`
	`137`	`+ override protected def typedScala2MacroBody(call: untpd.Tree)(using Context): Tree = promote(call)`
`137`	`138`	`}`
Original file line number	Diff line number	Diff line change
`@@ -4,7 +4,7 @@`
`4`	`4`	`\|no implicit argument of type scala.scalajs.js.ConstructorTag[ScalaClass] was found for parameter tag of method constructorTag in package scala.scalajs.js.`
`5`	`5`	`\|I found:`
`6`	`6`	`\|`
`7`		`- \| scala.scalajs.js.ConstructorTag.materialize[Nothing]`
	`7`	`+ \| scala.scalajs.js.ConstructorTag.materialize[T]`
`8`	`8`	`\|`
`9`	`9`	`\|But method materialize in object ConstructorTag does not match type scala.scalajs.js.ConstructorTag[ScalaClass].`
`10`	`10`	`-- Error: tests/neg-scalajs/jsconstructortag-error-in-typer.scala:10:39 ------------------------------------------------`
`@@ -13,7 +13,7 @@`
`13`	`13`	`\|no implicit argument of type scala.scalajs.js.ConstructorTag[ScalaTrait] was found for parameter tag of method constructorTag in package scala.scalajs.js.`
`14`	`14`	`\|I found:`
`15`	`15`	`\|`
`16`		`- \| scala.scalajs.js.ConstructorTag.materialize[Nothing]`
	`16`	`+ \| scala.scalajs.js.ConstructorTag.materialize[T]`
`17`	`17`	`\|`
`18`	`18`	`\|But method materialize in object ConstructorTag does not match type scala.scalajs.js.ConstructorTag[ScalaTrait].`
`19`	`19`	`-- Error: tests/neg-scalajs/jsconstructortag-error-in-typer.scala:11:45 ------------------------------------------------`
`@@ -22,6 +22,6 @@`
`22`	`22`	`\|no implicit argument of type scala.scalajs.js.ConstructorTag[ScalaObject.type] was found for parameter tag of method constructorTag in package scala.scalajs.js.`
`23`	`23`	`\|I found:`
`24`	`24`	`\|`
`25`		`- \| scala.scalajs.js.ConstructorTag.materialize[Nothing]`
	`25`	`+ \| scala.scalajs.js.ConstructorTag.materialize[T]`
`26`	`26`	`\|`
`27`	`27`	`\|But method materialize in object ConstructorTag does not match type scala.scalajs.js.ConstructorTag[ScalaObject.type].`
Original file line number	Diff line number	Diff line change
`@@ -4,6 +4,6 @@`
`4`	`4`	`\|Cannot construct a collection of type List[String] with elements of type Int based on a collection of type List[Int]..`
`5`	`5`	`\|I found:`
`6`	`6`	`\|`
`7`		`- \| collection.BuildFrom.buildFromIterableOps[Nothing, Nothing, Nothing]`
	`7`	`+ \| collection.BuildFrom.buildFromIterableOps[CC, A0, A]`
`8`	`8`	`\|`
`9`	`9`	`\|But method buildFromIterableOps in trait BuildFromLowPriority2 does not match type collection.BuildFrom[List[Int], Int, List[String]].`
Original file line number	Diff line number	Diff line change
`@@ -6,5 +6,5 @@ object C {`
`6`	`6`	`trait X[T]`
`7`	`7`	`implicit def u[A, B]: X[A \| B] = new X[A \| B] {}`
`8`	`8`	`def y[T](implicit x: X[T]): T = ???`
`9`		`- val x: a.type & b.type \| b.type & c.type = y`
	`9`	`+ val x: a.type & b.type \| b.type & c.type = y // error`
`10`	`10`	`}`
Original file line number	Diff line number	Diff line change
`@@ -344,5 +344,6 @@ object functors {`
`344`	`344`	`??? // $this.flatMap[A](identity) disabled since it does not typecheck`
`345`	`345`	`}`
`346`	`346`
`347`		`- MonadFlatten.flattened(List(List(1, 2, 3), List(4, 5)))`
	`347`	`+ MonadFlatten.flattened(List(List(1, 2, 3), List(4, 5))) // ok, synthesizes (using ListMonad)`
	`348`	`+ MonadFlatten.flattened(List(List(1, 2, 3), List(4, 5)))(using ListMonad) // error`
`348`	`349`	`}`