Fix type test for trait parameter arguments

Fixes #11993

Author: odersky

compiler/src/dotty/tools/dotc/ast/TreeInfo.scala

@@ -652,7 +652,7 @@ trait TypedTreeInfo extends TreeInfo[Type] { self: Trees.Instance[Type] =>
     }
   }
 
-  /** The type arguemnts of a possibly curried call */
+  /** The type arguments of a possibly curried call */
   def typeArgss(tree: Tree): List[List[Tree]] =
     @tailrec
     def loop(tree: Tree, argss: List[List[Tree]]): List[List[Tree]] = tree match
@@ -661,7 +661,7 @@ trait TypedTreeInfo extends TreeInfo[Type] { self: Trees.Instance[Type] =>
       case _ => argss
     loop(tree, Nil)
 
-  /** The term arguemnts of a possibly curried call */
+  /** The term arguments of a possibly curried call */
   def termArgss(tree: Tree): List[List[Tree]] =
     @tailrec
     def loop(tree: Tree, argss: List[List[Tree]]): List[List[Tree]] = tree match
@@ -670,7 +670,7 @@ trait TypedTreeInfo extends TreeInfo[Type] { self: Trees.Instance[Type] =>
       case _ => argss
     loop(tree, Nil)
 
-  /** The type and term arguemnts of a possibly curried call, in the order they are given */
+  /** The type and term arguments of a possibly curried call, in the order they are given */
   def allArgss(tree: Tree): List[List[Tree]] =
     @tailrec
     def loop(tree: Tree, argss: List[List[Tree]]): List[List[Tree]] = tree match

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

@@ -2199,6 +2199,10 @@ object SymDenotations {
     def paramAccessors(using Context): List[Symbol] =
       unforcedDecls.filter(_.is(ParamAccessor))
 
+    /** The term parameter getters of this class. */
+    def paramGetters(using Context): List[Symbol] =
+      paramAccessors.filterNot(_.isSetter)
+
     /** If this class has the same `decls` scope reference in `phase` and
      *  `phase.next`, install a new denotation with a cloned scope in `phase.next`.
      */

compiler/src/dotty/tools/dotc/reporting/ErrorMessageID.scala

@@ -154,7 +154,7 @@ enum ErrorMessageID extends java.lang.Enum[ErrorMessageID] {
     ErasedTypesCanOnlyBeFunctionTypesID,
     CaseClassMissingNonImplicitParamListID,
     EnumerationsShouldNotBeEmptyID,
-    UNUSED_1,
+    IllegalParameterInitID,
     RedundantModifierID,
     TypedCaseDoesNotExplicitlyExtendTypedEnumID,
     IllegalRedefinitionOfStandardKindID,

compiler/src/dotty/tools/dotc/reporting/messages.scala

@@ -1467,6 +1467,14 @@ import transform.SymUtils._
     def msg = em"""$tp does not conform to its self type $selfType; cannot be instantiated"""
   }
 
+  class IllegalParameterInit(found: Type, expected: Type, param: Symbol, cls: Symbol)(using Context)
+    extends TypeMismatchMsg(found, expected)(IllegalParameterInitID):
+    def msg =
+      em"""illegal parameter initialization of $param.
+          |
+          |  The argument passed for $param has type: $found
+          |  but $cls expects $param to have type: $expected"""
+
   class AbstractMemberMayNotHaveModifier(sym: Symbol, flag: FlagSet)(
     implicit ctx: Context)
     extends SyntaxMsg(AbstractMemberMayNotHaveModifierID) {

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

@@ -132,7 +132,7 @@ class Constructors extends MiniPhase with IdentityDenotTransformer { thisPhase =
     // Produce aligned accessors and constructor parameters. We have to adjust
     // for any outer parameters, which are last in the sequence of original
     // parameter accessors but come first in the constructor parameter list.
-    val accessors = cls.paramAccessors.filterNot(x => x.isSetter)
+    val accessors = cls.paramGetters
     val vparamsWithOuterLast = vparams match {
       case vparam :: rest if vparam.name == nme.OUTER => rest ::: vparam :: Nil
       case _ => vparams

compiler/src/dotty/tools/dotc/typer/RefChecks.scala

@@ -26,7 +26,7 @@ import Constants.Constant
 import NullOpsDecorator._
 
 object RefChecks {
-  import tpd.{Tree, MemberDef, NamedArg, Literal, Template, DefDef}
+  import tpd._
 
   val name: String = "refchecks"
 
@@ -133,6 +133,27 @@ object RefChecks {
               false
           }
 
+      /** Check that arguments passed to trait parameters conform to the parameter types
+       *  in the current class. This is necessary since parameter types might be narrowed
+       *  through intersection with other parent traits. See neg/i11018.scala.
+       *  
+      def checkParamInits(app: Apply): Unit =
+        val parentCls = app.tpe.classSymbol
+        if parentCls.is(Trait) then
+          val params = parentCls.asClass.paramGetters
+          val args = termArgss(app).flatten
+          for (param, arg) <- params.lazyZip(args) do
+            if !param.is(Private) then // its type can be narrowed through intersection -> a check is needed
+              val paramType = cls.thisType.memberInfo(param)
+              if !(arg.tpe <:< paramType) then
+                val argTypes = args.tpes
+                // it could still be OK but we might need to substitute arguments for parameters
+                // to account for dependent parameters. See pos/i11993.scala
+                if !(arg.tpe.subst(params, argTypes) <:< paramType.subst(params, argTypes))
+                then
+                  report.error(IllegalParameterInit(arg.tpe, paramType, param, cls), arg.srcPos)
+
+      for case app: Apply <- parentTrees do checkParamInits(app)
     case _ =>
   }
 
@@ -801,34 +822,7 @@ object RefChecks {
         report.error(problem(), clazz.srcPos)
       }
 
-      // check that basetype and subtype agree on types of trait parameters
-      //
-      // I.e. trait and class parameters not only need to conform to the expected
-      // type of the corresponding base-trait, but also to the type as seen by the
-      // inheriting subtype.
-      def checkTraitParametersOK() = for {
-        parent <- clazz.info.parents
-        parentSym = parent.classSymbol
-        if parentSym.isClass
-        cls = parentSym.asClass
-        if cls.paramAccessors.nonEmpty
-        param <- cls.paramAccessors
-      } {
-        val tpeFromParent = parent.memberInfo(param)
-        val tpeFromClazz = clazz.thisType.memberInfo(param)
-        if (!(tpeFromParent <:< tpeFromClazz)) {
-          val msg =
-            em"""illegal parameter: The types of $param do not match.
-                |
-                |  $param in $cls has type: $tpeFromParent
-                |  but $clazz expects $param to have type: $tpeFromClazz"""
-
-          report.error(msg, clazz.srcPos)
-        }
-      }
-
       checkParameterizedTraitsOK()
-      checkTraitParametersOK()
     }
 
     /** Check that `site` does not inherit conflicting generic instances of `baseCls`,

tests/generic-java-signatures/derivedNames.scala

@@ -9,7 +9,7 @@ object Test {
     if (scala.util.Properties.isWin)
       assert(returnType.toString == out1 || returnType.toString == out2)
     else if (scala.util.Properties.isMac)
-      assert(returnType.toString == out1)
+      assert(returnType.toString == out1, s"$returnType != $out1")
     else
       assert(returnType.toString == out2)
   }

tests/neg/i3989f.scala

@@ -3,7 +3,7 @@ object Test extends App {
   class B[+X](val y: X) extends A[X](y)
   class C extends B(5) with A[String] // error: illegal inheritance
 
-  class D extends B(5) with A[Any] // error: illegal parameter
+  class D extends B(5) with A[Any]
 
   def f(a: A[Int]): String = a match {
     case c: C => c.x

tests/pos/i11993.scala

@@ -0,0 +1,15 @@
+object test1:
+  class Foo(
+    val x: String,
+    val y: Option[x.type]
+  )
+
+  class Bar extends Foo("bar", Some("bar"))
+
+object test2:
+  trait Foo(
+    val x: String,
+    val y: Option[x.type]
+  )
+
+  class Bar extends Foo("bar", Some("bar"))