Generalize overriding checking from isDefined

Generalize overriding checking from isDefined
to all methods added by desugar to a case class.
None of these methods has an override so we
need to add one in case they do override another method
(previously we would flag this as an error).

3 files changed, 9 insertions, 1 deletions

diff --git a/src/dotty/tools/dotc/ast/Desugar.scala b/src/dotty/tools/dotc/ast/Desugar.scala
index 72dd8cb4c..12f3e4406 100644
--- a/src/dotty/tools/dotc/ast/Desugar.scala
+++ b/src/dotty/tools/dotc/ast/Desugar.scala
@@ -21,6 +21,13 @@ object desugar {
   /** Info of a variable in a pattern: The named tree and its type */
   private type VarInfo = (NameTree, Tree)
 
+  /** Names of methods that are added unconditionally to case classes */
+  def isDesugaredCaseClassMethodName(name: Name)(implicit ctx: Context) =
+    name == nme.isDefined ||
+    name == nme.copy ||
+    name == nme.productArity ||
+    name.isSelectorName
+
 // ----- DerivedTypeTrees -----------------------------------
 
   class SetterParamTree extends DerivedTypeTree {
diff --git a/src/dotty/tools/dotc/core/NameOps.scala b/src/dotty/tools/dotc/core/NameOps.scala
index 7dbd492b4..6c1930c9f 100644
--- a/src/dotty/tools/dotc/core/NameOps.scala
+++ b/src/dotty/tools/dotc/core/NameOps.scala
@@ -81,6 +81,7 @@ object NameOps {
     def isScala2LocalSuffix = name.endsWith(" ")
     def isModuleVarName(name: Name): Boolean =
       name.stripAnonNumberSuffix endsWith MODULE_VAR_SUFFIX
+    def isSelectorName = name.startsWith(" ") && name.tail.forall(_.isDigit)
 
     /** Is name a variable name? */
     def isVariableName: Boolean = name.length > 0 && {
diff --git a/src/dotty/tools/dotc/typer/RefChecks.scala b/src/dotty/tools/dotc/typer/RefChecks.scala
index 416a2cb92..44d5ee576 100644
--- a/src/dotty/tools/dotc/typer/RefChecks.scala
+++ b/src/dotty/tools/dotc/typer/RefChecks.scala
@@ -288,7 +288,7 @@ object RefChecks {
                  !member.isAnyOverride) {
         // (*) Exclusion for default getters, fixes SI-5178. We cannot assign the Override flag to
         // the default getter: one default getter might sometimes override, sometimes not. Example in comment on ticket.
-        if (member.name == nme.isDefined && member.is(Synthetic)) // isDefined methods are added automatially, can't have an override preset.
+        if (member.is(Synthetic) && desugar.isDesugaredCaseClassMethodName(member.name)) // such names are added automatically, can't have an override preset.
           member.setFlag(Override)
         else if (member.owner != clazz && other.owner != clazz && !(other.owner derivesFrom member.owner))
           emitOverrideError(