Check trait overrides trait parameters

Author: liufengyun

compiler/src/dotty/tools/dotc/transform/init/ParamOverridingCheck.scala

@@ -150,6 +150,23 @@ object ParamOverridingCheck:
 
       init(tpl, thisRef, classSym)
 
+      // check parameter access semantics
+      for
+        klass <- classSym.parentSyms
+        paramSym <- klass.asClass.paramGetters
+        overridingClass <- (classSym :: classSym.parentSyms).filter(cls => cls != klass && cls.isSubClass(klass))
+        overridingSym = paramSym.overridingSymbol(overridingClass.asClass) if overridingSym.exists
+      do
+        // println(paramSym.show + " is overridden in " + thisRef.klass)
+        if !overridingSym.is(Flags.ParamAccessor) then
+          report.warning("Overriding parameter " + paramSym.show + " in " + klass.show + " as non-parameter in " + overridingSym.owner.show, overridingSym.defTree)
+        else
+          val overridingValue = thisRef.field(overridingSym)
+          if thisRef.field(paramSym) != overridingValue then
+            // println(overridingSym.show + " in " + thisRef.klass + " = " + overridingValue)
+            // println(paramSym.show + " in " + klass + " = " + thisRef.field(paramSym))
+            report.warning("Incorrect overriding: " + paramSym.show + " in " + klass.show + " has a different value from " + overridingSym.show + " in " + overridingSym.owner.show, overridingSym.defTree)
+
   // ---------------------- Semantic definition --------------------------------
 
   /** Evaluate a list of expressions */
@@ -248,7 +265,7 @@ object ParamOverridingCheck:
   }
 
   /** Initialize part of an abstract object in `klass` of the inheritance chain */
-  def init(tpl: Template, thisV: ThisRef, klass: ClassSymbol): Contextual[Value] = log("init " + klass.show, printer) {
+  def init(tpl: Template, thisV: ThisRef, klass: ClassSymbol): Contextual[Unit] = log("init " + klass.show, printer) {
     val paramsMap = tpl.constr.termParamss.flatten.map { vdef =>
       vdef.name -> thisV.field(vdef.symbol)
     }.toMap
@@ -323,21 +340,4 @@ object ParamOverridingCheck:
     end if
 
     // skip class body
-
-    // check parameter access semantics
-    for
-      paramSym <- klass.paramGetters
-      overridingSym = paramSym.overridingSymbol(thisV.klass) if overridingSym.exists
-    do
-      // println(paramSym.show + " is overridden in " + thisV.klass)
-      if !overridingSym.is(Flags.ParamAccessor) then
-        report.warning("Overriding parameter " + paramSym.show + " in " + klass.show + " as non-parameter in " + overridingSym.owner.show, overridingSym.defTree)
-      else
-        val overridingValue = thisV.field(overridingSym)
-        if thisV.field(paramSym) != overridingValue then
-          // println(overridingSym.show + " in " + thisV.klass + " = " + overridingValue)
-          // println(paramSym.show + " in " + klass + " = " + thisV.field(paramSym))
-          report.warning("Incorrect overriding: " + paramSym.show + " in " + klass.show + " has a different value from " + overridingSym.show + " in " + overridingSym.owner.show, overridingSym.defTree)
-
-    thisV
   }

tests/init/neg/i15764e.scala

@@ -0,0 +1,18 @@
+trait A(val x: Int)
+trait B(override val x: Int) extends A // error
+class C extends B(1) with A(2)
+
+
+trait X(val x: Int)
+trait Y(override val x: Int) extends X // error
+class Z extends X(1) with Y(2)
+
+object Pos1:
+  trait X(val x: Int)
+  trait Y(override val x: Int) extends X // ok
+  class Z(n: Int) extends X(n) with Y(n)
+
+object Pos2:
+  trait X(val x: Int)
+  trait Y(override val x: Int) extends X // ok
+  class Z(n: Int) extends Y(n) with X(n)

tests/init/pos/i15764e.scala

@@ -1,7 +1,3 @@
 trait X(val x: Int, y: Int, z: Int)
 trait Y(override val x: Int, y: Int, z: Int) extends X
 class Z(override val x: Int, y: Int, z: Int) extends Y(x, y, z) with X(x, y, z)
-
-trait A(val x: Int, y: Int, z: Int)
-trait B(override val x: Int, y: Int, z: Int) extends A
-class C extends B(1, 2, 3) with A(1, 2, 3)