Merge pull request #7708 from dotty-staging/fix-#7630

Fix #7630: Use weak conformance in overloading resolution

Author: odersky

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

@@ -666,7 +666,8 @@ trait Applications extends Compatibility {
    * argument trees.
    */
   class ApplicableToTreesDirectly(methRef: TermRef, targs: List[Type], args: List[Tree], resultType: Type)(implicit ctx: Context) extends ApplicableToTrees(methRef, targs, args, resultType)(ctx) {
-    override def argOK(arg: TypedArg, formal: Type): Boolean = argType(arg, formal) <:< formal.widenExpr
+    override def argOK(arg: TypedArg, formal: Type): Boolean =
+      argType(arg, formal) relaxed_<:< formal.widenExpr
   }
 
   /** Subclass of Application for applicability tests with value argument types. */

tests/neg/harmonize.scala

@@ -1,3 +1,4 @@
+import collection.mutable.ArrayBuffer
 object Test {
 
   def main(args: Array[String]) = {
@@ -50,20 +51,37 @@ object Test {
 
   }
 
-  inline val b = 33
-  def f(): Int = b + 1
-  val a1 = Array(b, 33, 'a')
-  val b1: Array[Int] = a1    // error: no widening
-  val a2 = Array(b, 33, 'a', f())
-  val b2: Array[Int] = a2    // error: no widening
-  val a3 = Array(1.0f, 'a', 0)
-  val b3: Array[Float] = a3  // error: no widening
-  val a4 = Array(1.0f, 1L)
-  val b4: Array[Double] = a4 // error: no widening
-  val a5 = Array(1.0f, 1L, f())
-  val b5: Array[AnyVal] = a5
-  val a6 = Array(1.0f, 1234567890)
-  val b6: Array[AnyVal] = a6
+  def arraytest =
+    inline val b = 33
+    def f(): Int = b + 1
+    val a1 = Array(b, 33, 'a')
+    val b1: Array[Int] = a1    // OK, Array constructor selection uses weak conformance
+    val a2 = Array(b, 33, 'a', f())
+    val b2: Array[Int] = a2    // OK, Array constructor selection uses weak conformance
+    val a3 = Array(1.0f, 'a', 0)
+    val b3: Array[Float] = a3  // OK, Array constructor selection uses weak conformance
+    val a4 = Array(1.0f, 1L)
+    val b4: Array[Double] = a4 // error: Array[Float] is picked
+    val a5 = Array(1.0f, 1L, f())
+    val b5: Array[AnyVal] = a5 // error: Array[Float] is picked
+    val a6 = Array(1.0f, 1234567890)
+    val b6: Array[AnyVal] = a6 // error: Array[Float] is picked
+
+  def arrayBufferTest =
+    inline val b = 33
+    def f(): Int = b + 1
+    val a1 = ArrayBuffer(b, 33, 'a')
+    val b1: ArrayBuffer[Int] = a1    // error: no widening
+    val a2 = ArrayBuffer(b, 33, 'a', f())
+    val b2: ArrayBuffer[Int] = a2    // error: no widening
+    val a3 = ArrayBuffer(1.0f, 'a', 0)
+    val b3: ArrayBuffer[Float] = a3  // error: no widening
+    val a4 = ArrayBuffer(1.0f, 1L)
+    val b4: ArrayBuffer[Double] = a4 // error: no widening
+    val a5 = ArrayBuffer(1.0f, 1L, f())
+    val b5: ArrayBuffer[AnyVal] = a5
+    val a6 = ArrayBuffer(1.0f, 1234567890)
+    val b6: ArrayBuffer[AnyVal] = a6
 
   def totalDuration(results: List[Long], cond: Boolean): Long =
     results.map(r => if (cond) r else 0).sum

tests/run/i7630.check

@@ -0,0 +1 @@
+2

tests/run/i7630.scala

@@ -0,0 +1,19 @@
+object Asserts {
+  def assertEquals(expected: Any, actual: Any): Unit = {
+    println(1)
+    assert(expected.equals(actual), s"expected $expected but got $actual")
+  }
+
+  def assertEquals(expected: Long, actual: Long): Unit = {
+    println(2)
+    assert(expected == actual, s"expected $expected but got $actual")
+  }
+}
+
+object Test {
+  def main(args: Array[String]): Unit = {
+    def foo(): Long = 42L
+
+    Asserts.assertEquals(42, foo()) // an Int and a Long
+  }
+}

tests/run/weak-conformance.scala

@@ -1,3 +1,4 @@
+import collection.mutable.ArrayBuffer
 object Test extends App {
   inline val b = 33
 
@@ -22,14 +23,35 @@ object Test extends App {
 
   locally {
     def f(): Int = b + 1
-    val x1 = Array(b, 33, 5.5)      ; x1: Array[Double] // b is an inline val
-    val x2 = Array(f(), 33, 5.5)    ; x2: Array[AnyVal] // f() is not a constant
+    val x1 = ArrayBuffer(b, 33, 5.5)      ; x1: ArrayBuffer[Double] // b is an inline val
+    val x2 = ArrayBuffer(f(), 33, 5.5)    ; x2: ArrayBuffer[AnyVal] // f() is not a constant
+    val x3 = ArrayBuffer(5, 11L)          ; x3: ArrayBuffer[Long]
+    val x4 = ArrayBuffer(5, 11L, 5.5)     ; x4: ArrayBuffer[AnyVal] // Long and Double found
+    val x5 = ArrayBuffer(1.0f, 2)         ; x5: ArrayBuffer[Float]
+    val x6 = ArrayBuffer(1.0f, 1234567890); x6: ArrayBuffer[AnyVal] // loss of precision
+    val x7 = ArrayBuffer(b, 33, 'a')      ; x7: ArrayBuffer[Char]
+    val x8 = ArrayBuffer(5.toByte, 11)    ; x8: ArrayBuffer[Byte]
+
+    val x9: ArrayBuffer[AnyVal] = ArrayBuffer(1.0f, 0)
+    assert(x9(0).getClass == classOf[java.lang.Float])
+    assert(x9(1).getClass == classOf[java.lang.Integer]) // expected type fully defined since ArrayBuffer is nonvariant
+    val x10 = ArrayBuffer[Any](1.0f, 0)
+    assert(x10(0).getClass == classOf[java.lang.Float])
+    assert(x10(1).getClass == classOf[java.lang.Integer])
+  }
+
+  locally {
+    // Arrays behave differently from lists since they have overloaded constructors, and weak
+    // conformance does apply for selecting one. See Issue #7630.
+    def f(): Int = b + 1
+    val x1 = Array(b, 33, 5.5)      ; x1: Array[Double]
+    val x2 = Array(f(), 33, 5.5)    ; x2: Array[Double]
     val x3 = Array(5, 11L)          ; x3: Array[Long]
-    val x4 = Array(5, 11L, 5.5)     ; x4: Array[AnyVal] // Long and Double found
+    val x4 = Array(5, 11L, 5.5)     ; x4: Array[Double]
     val x5 = Array(1.0f, 2)         ; x5: Array[Float]
-    val x6 = Array(1.0f, 1234567890); x6: Array[AnyVal] // loss of precision
-    val x7 = Array(b, 33, 'a')      ; x7: Array[Char]
-    val x8 = Array(5.toByte, 11)    ; x8: Array[Byte]
+    val x6 = Array(1.0f, 1234567890); x6: Array[Float]
+    val x7 = Array(b, 33, 'a')      ; x7: Array[Int]
+    val x8 = Array(5.toByte, 11)    ; x8: Array[Int]
 
     val x9: Array[AnyVal] = Array(1.0f, 0)
     assert(x9(0).getClass == classOf[java.lang.Float])