Avoid parameter name clashes in export forwarders

scala · Feb 19, 2022 · 42e470f · 42e470f
1 parent 8e529b1
commit 42e470f
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Showing 3 changed files with 30 additions and 6 deletions.
diff --git a/compiler/src/dotty/tools/dotc/typer/Namer.scala b/compiler/src/dotty/tools/dotc/typer/Namer.scala
@@ -1170,11 +1170,28 @@ class Namer { typer: Typer =>
                 then
                   (StableRealizable, ExprType(pathType.select(sym)))
                 else
-                  def addPathMethodParams(pt: Type, info: Type): Type = pt match
-                    case pt: MethodOrPoly =>
-                      pt.derivedLambdaType(resType = addPathMethodParams(pt.resType, info))
-                    case _ =>
-                      info
+                  def addPathMethodParams(pathType: Type, info: Type): Type =
+                    def defines(pt: Type, pname: Name): Boolean = pt match
+                      case pt: MethodOrPoly =>
+                        pt.paramNames.contains(pname) || defines(pt.resType, pname)
+                      case _ =>
+                        false
+                    def avoidNameClashes(info: Type): Type = info match
+                      case info: MethodOrPoly =>
+                        info.derivedLambdaType(
+                          paramNames = info.paramNames.mapConserve {
+                            pname => if defines(pathType, pname) then pname.freshened else pname
+                          },
+                          resType = avoidNameClashes(info.resType))
+                      case info =>
+                        info
+                    def wrap(pt: Type, info: Type): Type = pt match
+                      case pt: MethodOrPoly =>
+                        pt.derivedLambdaType(resType = wrap(pt.resType, info))
+                      case _ =>
+                        info
+                    wrap(pathType, avoidNameClashes(info))
+
                   val mbrInfo =
                     if pathMethod.exists
                     then addPathMethodParams(pathMethod.info, mbr.info.widenExpr)

diff --git a/compiler/src/dotty/tools/dotc/typer/Typer.scala b/compiler/src/dotty/tools/dotc/typer/Typer.scala
@@ -2571,7 +2571,7 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
         val selectors1 = typedSelectors(exp.selectors)
         assignType(cpy.Export(exp)(expr1, selectors1))
       case _ =>
-        errorTree(exp, em"exports are only allowed from objects and classes")
+        errorTree(exp, em"exports are only allowed from objects and classes, they can not belong to local blocks")
 
   def typedPackageDef(tree: untpd.PackageDef)(using Context): Tree =
     val pid1 = withMode(Mode.InPackageClauseName)(typedExpr(tree.pid, AnySelectionProto))

diff --git a/tests/pos/export-in-extension-rename.scala b/tests/pos/export-in-extension-rename.scala
@@ -0,0 +1,7 @@
+class Ops[A](xs: List[A]):
+  def map[B](x: A => B): List[B] = ???
+
+extension [B](x: List[B])
+  private def ops = new Ops[B](x)
+  export ops.map  // `x` and `B` should not appear twice as a parameter
+