Fix/24886 extension using defaults

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

@@ -2037,7 +2037,9 @@ trait Applications extends Compatibility {
     def isAsGood(alt1: TermRef, tp1: Type, alt2: TermRef, tp2: Type): Boolean = trace(i"isAsGood $tp1 $tp2", overload) {
       tp1 match
         case tp1: MethodType => // (1)
-          tp1.paramInfos.isEmpty && tp2.isInstanceOf[LambdaType]
+          tp1.paramInfos.isEmpty
+          && tp2.isInstanceOf[LambdaType]
+          && !tp2.isVarArgsMethod
           || {
             if tp1.isVarArgsMethod then
               tp2.isVarArgsMethod

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

@@ -1373,10 +1373,14 @@ trait Checking {
           if decl.name.is(DefaultGetterName) && ctx.reporter.errorsReported then
             () // do nothing; we already have reported an error that overloaded variants cannot have default arguments
           else if decl.is(Synthetic) then doubleDefError(other, decl)
-          else doubleDefError(decl, other)
-        if decl.hasDefaultParams && other.hasDefaultParams then
-          report.error(em"two or more overloaded variants of $decl have default arguments", decl.srcPos)
-          decl.resetFlag(HasDefaultParams)
+          else
+            doubleDefError(decl, other)
+            if decl.hasDefaultParams && other.hasDefaultParams then
+
+              report.error(em"two or more overloaded variants of $decl have default arguments", decl.srcPos)
+              decl.resetFlag(HasDefaultParams)
+
+
       if !excludeFromDoubleDeclCheck(decl) then
         seen(decl.name) = decl :: seen(decl.name)
 

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

@@ -59,12 +59,30 @@ object RefChecks {
         if (haveDefaults.length > 1) {
           val owners = haveDefaults map (_.owner)
           // constructors of different classes are allowed to have defaults
-          if (haveDefaults.exists(x => !x.isConstructor) || owners.distinct.size < haveDefaults.size)
-            report.error(
-              em"in $clazz, multiple overloaded alternatives of ${haveDefaults.head} define default arguments${
-                  if owners.forall(_ == clazz) then "."
-                  else i".\nThe members with defaults are defined in ${owners.map(_.showLocated).mkString("", " and ", ".")}"}",
-              clazz.srcPos)
+          if (haveDefaults.exists(x => !x.isConstructor) || owners.distinct.size < haveDefaults.size) {
+            def generatedDefaultGetters(sym: Symbol)(using Context): Set[TermName] =
+              val paramSyms = sym.paramSymss.flatten.filter(_.isTerm)
+              val defaults = paramSyms.zipWithIndex.collect {
+                case (p, i) if p.is(HasDefault) =>
+                  DefaultGetterName(sym.name.asTermName, i + 1)
+              }
+              defaults.toSet
+
+            val defaults = haveDefaults.map(generatedDefaultGetters)
+            val hasCollision = defaults.combinations(2).exists { case List(d1, d2) =>
+              d1.intersect(d2).nonEmpty
+            }
+
+            if hasCollision then
+              report.error(
+                em"in $clazz, multiple overloaded alternatives of ${haveDefaults.head} define default arguments${
+                    if owners.forall(_ == clazz) then "."
+                    else i".\nThe members with defaults are defined in ${owners.map(_.showLocated).mkString("", " and ", ".")}"}",
+                clazz.srcPos)
+          }
+
+
+
         }
       }
     }

tests/pos/i24886.scala

@@ -0,0 +1,17 @@
+
+package i24886
+
+var default: Option[String] = Some("test")
+var value: String = "0"
+
+extension (self: String)
+  (using key: () => String = () => default.get)
+
+  def int(`type`: String = "an integer"): Int =
+    try
+      self.toInt
+    catch _ => throw new RuntimeException(`type`)
+
+def int(`type`: String = "an integer"): Int = value.int(`type`)
+
+