-Xsource-features:double-definitions

Author: som-snytt

src/compiler/scala/tools/nsc/Global.scala

@@ -1195,6 +1195,7 @@ class Global(var currentSettings: Settings, reporter0: Reporter)
       def leadingInfix           = isScala3 && contains(o.leadingInfix)
       def packagePrefixImplicits = isScala3 && contains(o.packagePrefixImplicits)
       def implicitResolution     = isScala3 && contains(o.implicitResolution) || settings.Yscala3ImplicitResolution.value
+      def doubleDefinitions      = isScala3 && contains(o.doubleDefinitions)
     }
 
     // used in sbt

src/compiler/scala/tools/nsc/settings/ScalaSettings.scala

@@ -181,6 +181,7 @@ trait ScalaSettings extends StandardScalaSettings with Warnings { _: MutableSett
     val leadingInfix           = Choice("leading-infix", "Leading infix operators continue the previous line.")
     val packagePrefixImplicits = Choice("package-prefix-implicits", "The package prefix p is no longer part of the implicit search scope for type p.A.")
     val implicitResolution     = Choice("implicit-resolution", "Use Scala-3-style downwards comparisons for implicit search and overloading resolution (see github.com/scala/scala/pull/6037).")
+    val doubleDefinitions      = Choice("double-definitions", "Correctly disallow double definitions differing in empty parens.")
 
     val v13_13_choices = List(caseApplyCopyAccess, caseCompanionFunction, inferOverride, any2StringAdd, unicodeEscapesRaw, stringContextScope, leadingInfix, packagePrefixImplicits)
 
@@ -190,11 +191,16 @@ trait ScalaSettings extends StandardScalaSettings with Warnings { _: MutableSett
       expandsTo = v13_13_choices)
 
     val v13_14_choices = implicitResolution :: v13_13_choices
-
     val v13_14 = Choice(
       "v2.13.14",
       "v2.13.13 plus implicit-resolution",
       expandsTo = v13_14_choices)
+
+    val v13_15_choices = doubleDefinitions :: v13_14_choices
+    val v13_15 = Choice(
+      "v2.13.15",
+      "v2.13.14 plus double-definitions",
+      expandsTo = v13_15_choices)
   }
   val XsourceFeatures = MultiChoiceSetting(
     name = "-Xsource-features",

src/compiler/scala/tools/nsc/typechecker/Typers.scala

@@ -3438,7 +3438,12 @@ trait Typers extends Adaptations with Tags with TypersTracking with PatternTyper
               }
               nn(sym) && nn(sym1)
             }
-            val conflicted = inBlock || (!sym.isMethod && !sym1.isMethod) || nullaryNilary || sym.tpe.matches(sym1.tpe)
+            def correctly: Boolean = nullaryNilary.tap(if (_) reportCorrection()) && currentRun.sourceFeatures.doubleDefinitions
+            def reportCorrection(): Unit =
+              if (currentRun.isScala3 && !currentRun.sourceFeatures.doubleDefinitions)
+                context.warning(sym.pos, s"Double definition will be detected in Scala 3; the conflicting $sym1 is defined at ${sym1.pos.line}:${sym1.pos.column}", Scala3Migration)
+
+            val conflicted = inBlock || (!sym.isMethod && !sym1.isMethod) || sym.tpe.matches(sym1.tpe) || correctly
 
             // default getters are defined twice when multiple overloads have defaults.
             // The error for this is deferred until RefChecks.checkDefaultsInOverloaded

test/files/neg/i20006.check

@@ -6,18 +6,10 @@ i20006.scala:7: error: method hasNext is defined twice;
   the conflicting value hasNext was defined at line 5:7
   override def hasNext: Boolean = first || hasNext(acc) // error
                ^
-i20006.scala:22: error: method next is defined twice;
-  the conflicting value next was defined at line 18:65
-  override def next(): T = { // error
-               ^
 i20006.scala:21: error: method hasNext is defined twice;
   the conflicting value hasNext was defined at line 18:42
   override def hasNext: Boolean = first || hasNext(acc) // error
                ^
-i20006.scala:36: error: method next is defined twice;
-  the conflicting value next was defined at line 32:65
-  def next(): T = { // error
-      ^
 i20006.scala:35: error: method hasNext is defined twice;
   the conflicting value hasNext was defined at line 32:42
   def hasNext: Boolean = first || hasNext(acc) // error
@@ -32,16 +24,11 @@ i20006.scala:50: error: variable x is defined twice;
 i20006.scala:53: error: x is already defined as value x
   private[this] var x: Int = 42 // error
                     ^
-i20006.scala:56: error: method x is defined twice;
-  the conflicting value x was defined at line 55:9
-  def x(): Int = 42 // error
-      ^
-i20006.scala:63: error: method x is defined twice;
-  the conflicting value x was defined at line 62:21
-  def x(): Int = 42 // error
-      ^
 i20006.scala:67: error: method x is defined twice;
   the conflicting method x was defined at line 66:21
   def x(): Int = 42 // error
       ^
-12 errors
+i20006.scala:77: error: x is already defined as variable x
+    def x(): Int = x // error
+        ^
+9 errors

test/files/neg/i20006.scala

@@ -19,7 +19,7 @@ final class YIterateIterator[T](seed: T, hasNext: T => Boolean, next: T => T) ex
   private var first = true
   private var acc = seed
   override def hasNext: Boolean = first || hasNext(acc) // error
-  override def next(): T = { // error
+  override def next(): T = { // noerror
     if (first) {
       first = false
     } else {
@@ -33,7 +33,7 @@ final class ZIterateIterator[T](seed: T, hasNext: T => Boolean, next: T => T) {
   private var first = true
   private var acc = seed
   def hasNext: Boolean = first || hasNext(acc) // error
-  def next(): T = { // error
+  def next(): T = { // noerror
     if (first) {
       first = false
     } else {
@@ -53,94 +53,27 @@ class E(x: String) {
   private[this] var x: Int = 42 // error
 }
 class F(x: String) {
-  def x(): Int = 42 // error
+  def x(): Int = 42 // noerror
 }
 class G(x: String) {
   def x(i: Int): Int = i
 }
 class H {
   private[this] val x: String = ""
-  def x(): Int = 42 // error
+  def x(): Int = 42 // noerror
 }
 class I {
   private[this] def x: String = ""
   def x(): Int = 42 // error
 }
-
-/*
--- [E120] Naming Error: test/files/neg/i20006.scala:8:15 ---------------------------------------------------------------
-8 |  override def hasNext: Boolean = first || hasNext(acc)
-  |               ^
-  |               Double definition:
-  |               val hasNext: T => Boolean in class XIterateIterator at line 6 and
-  |               override def hasNext: Boolean in class XIterateIterator at line 8
--- [E120] Naming Error: test/files/neg/i20006.scala:9:15 ---------------------------------------------------------------
-9 |  override def next(): T = {
-  |               ^
-  |               Double definition:
-  |               val next: T => T in class XIterateIterator at line 7 and
-  |               override def next(): T in class XIterateIterator at line 9
--- [E120] Naming Error: test/files/neg/i20006.scala:22:15 --------------------------------------------------------------
-22 |  override def hasNext: Boolean = first || hasNext(acc)
-   |               ^
-   |               Double definition:
-   |               private[this] val hasNext: T => Boolean in class YIterateIterator at line 19 and
-   |               override def hasNext: Boolean in class YIterateIterator at line 22
--- [E120] Naming Error: test/files/neg/i20006.scala:23:15 --------------------------------------------------------------
-23 |  override def next(): T = {
-   |               ^
-   |               Double definition:
-   |               private[this] val next: T => T in class YIterateIterator at line 19 and
-   |               override def next(): T in class YIterateIterator at line 23
--- [E120] Naming Error: test/files/neg/i20006.scala:36:6 ---------------------------------------------------------------
-36 |  def hasNext: Boolean = first || hasNext(acc)
-   |      ^
-   |      Double definition:
-   |      private[this] val hasNext: T => Boolean in class ZIterateIterator at line 33 and
-   |      def hasNext: Boolean in class ZIterateIterator at line 36
--- [E120] Naming Error: test/files/neg/i20006.scala:37:6 ---------------------------------------------------------------
-37 |  def next(): T = {
-   |      ^
-   |      Double definition:
-   |      private[this] val next: T => T in class ZIterateIterator at line 33 and
-   |      def next(): T in class ZIterateIterator at line 37
--- [E120] Naming Error: test/files/neg/i20006.scala:48:6 ---------------------------------------------------------------
-48 |  val x: String = "member" // error
-   |      ^
-   |      Double definition:
-   |      private[this] val x: String in class C at line 47 and
-   |      val x: String in class C at line 48
--- [E120] Naming Error: test/files/neg/i20006.scala:51:14 --------------------------------------------------------------
-51 |  private var x: Int = 42 // error
-   |              ^
-   |              Double definition:
-   |              private[this] val x: String in class D at line 50 and
-   |              private[this] var x: Int in class D at line 51
--- [E120] Naming Error: test/files/neg/i20006.scala:54:20 --------------------------------------------------------------
-54 |  private[this] var x: Int = 42 // error
-   |                    ^
-   |                    Double definition:
-   |                    private[this] val x: String in class E at line 53 and
-   |                    private[this] var x: Int in class E at line 54
--- [E120] Naming Error: test/files/neg/i20006.scala:57:6 ---------------------------------------------------------------
-57 |  def x(): Int = 42 // error
-   |      ^
-   |      Double definition:
-   |      private[this] val x: String in class F at line 56 and
-   |      def x(): Int in class F at line 57
--- [E120] Naming Error: test/files/neg/i20006.scala:65:6 ---------------------------------------------------------------
-65 |  def x(): Int = 42
-   |      ^
-   |      Double definition:
-   |      val x: String in class H at line 63 and
-   |      def x(): Int in class H at line 65
--- Warning: test/files/neg/i20006.scala:54:16 --------------------------------------------------------------------------
-54 |  private[this] var x: Int = 42 // error
-   |                ^
-   |                Ignoring [this] qualifier.
-   |                This syntax will be deprecated in the future; it should be dropped.
-   |                See: https://docs.scala-lang.org/scala3/reference/dropped-features/this-qualifier.html
-   |                This construct can be rewritten automatically under -rewrite -source 3.4-migration.
-1 warning found
-11 errors found
-*/
+class PrivateConflict {
+  private[this] var x = 42
+  def x(): Int = x
+  def x_=(n: Int) = x = n
+}
+class LocalConflict {
+  def f(): Unit = {
+    var x = 42
+    def x(): Int = x // error
+  }
+}

test/files/neg/i20006b.check

@@ -0,0 +1,59 @@
+i20006b.scala:9: error: method next is defined twice;
+  the conflicting value next was defined at line 7:7
+  override def next(): T = { // error
+               ^
+i20006b.scala:8: error: method hasNext is defined twice;
+  the conflicting value hasNext was defined at line 6:7
+  override def hasNext: Boolean = first || hasNext(acc) // error
+               ^
+i20006b.scala:22: error: method hasNext is defined twice;
+  the conflicting value hasNext was defined at line 19:42
+  override def hasNext: Boolean = first || hasNext(acc) // error
+               ^
+i20006b.scala:36: error: method hasNext is defined twice;
+  the conflicting value hasNext was defined at line 33:42
+  def hasNext: Boolean = first || hasNext(acc) // error
+      ^
+i20006b.scala:48: error: x is already defined as value x
+  val x: String = "member" // error
+      ^
+i20006b.scala:51: error: variable x is defined twice;
+  the conflicting value x was defined at line 50:9
+  private var x: Int = 42 // error
+              ^
+i20006b.scala:54: error: x is already defined as value x
+  private[this] var x: Int = 42 // error
+                    ^
+i20006b.scala:68: error: method x is defined twice;
+  the conflicting method x was defined at line 67:21
+  def x(): Int = 42 // error
+      ^
+i20006b.scala:78: error: x is already defined as variable x
+    def x(): Int = x // error
+        ^
+i20006b.scala:23: error: Double definition will be detected in Scala 3; the conflicting value next is defined at 19:65
+Scala 3 migration messages are issued as errors under -Xsource:3. Use -Wconf or @nowarn to demote them to warnings or suppress.
+Applicable -Wconf / @nowarn filters for this fatal warning: msg=<part of the message>, cat=scala3-migration, site=YIterateIterator
+  override def next(): T = { // werror
+               ^
+i20006b.scala:37: error: Double definition will be detected in Scala 3; the conflicting value next is defined at 33:65
+Scala 3 migration messages are issued as errors under -Xsource:3. Use -Wconf or @nowarn to demote them to warnings or suppress.
+Applicable -Wconf / @nowarn filters for this fatal warning: msg=<part of the message>, cat=scala3-migration, site=ZIterateIterator
+  def next(): T = { // werror
+      ^
+i20006b.scala:57: error: Double definition will be detected in Scala 3; the conflicting value x is defined at 56:9
+Scala 3 migration messages are issued as errors under -Xsource:3. Use -Wconf or @nowarn to demote them to warnings or suppress.
+Applicable -Wconf / @nowarn filters for this fatal warning: msg=<part of the message>, cat=scala3-migration, site=F
+  def x(): Int = 42 // werror
+      ^
+i20006b.scala:64: error: Double definition will be detected in Scala 3; the conflicting value x is defined at 63:21
+Scala 3 migration messages are issued as errors under -Xsource:3. Use -Wconf or @nowarn to demote them to warnings or suppress.
+Applicable -Wconf / @nowarn filters for this fatal warning: msg=<part of the message>, cat=scala3-migration, site=H
+  def x(): Int = 42 // werror
+      ^
+i20006b.scala:72: error: Double definition will be detected in Scala 3; the conflicting variable x is defined at 71:21
+Scala 3 migration messages are issued as errors under -Xsource:3. Use -Wconf or @nowarn to demote them to warnings or suppress.
+Applicable -Wconf / @nowarn filters for this fatal warning: msg=<part of the message>, cat=scala3-migration, site=PrivateConflict
+  def x(): Int = x // werror
+      ^
+14 errors