Fix #9772: Normalize value definitions

compiler/src/dotty/tools/dotc/ast/Desugar.scala

@@ -147,24 +147,32 @@ object desugar {
 
 // ----- Desugar methods -------------------------------------------------
 
+  /** Setter generation is needed for:
+   *    - non-private class members
+   *    - all trait members
+   *    - all package object members
+   */
+  def isSetterNeeded(valDef: ValDef)(using Context): Boolean = {
+    val mods = valDef.mods
+    mods.is(Mutable)
+      && ctx.owner.isClass
+      && (!mods.is(Private) || ctx.owner.is(Trait) || ctx.owner.isPackageObject)
+  }
+
   /**   var x: Int = expr
    *  ==>
    *    def x: Int = expr
    *    def x_=($1: <TypeTree()>): Unit = ()
    *
-   *  Generate the setter only for
-   *    - non-private class members
-   *    - all trait members
-   *    - all package object members
+   *  Generate setter where needed
    */
   def valDef(vdef0: ValDef)(using Context): Tree = {
-    val vdef @ ValDef(name, tpt, rhs) = vdef0
+    val vdef @ ValDef(_, tpt, rhs) = vdef0
     val mods = vdef.mods
-    val setterNeeded =
-      mods.is(Mutable)
-      && ctx.owner.isClass
-      && (!mods.is(Private) || ctx.owner.is(Trait) || ctx.owner.isPackageObject)
-    if (setterNeeded) {
+
+    val valName = normalizeName(vdef, tpt).asTermName
+
+    if (isSetterNeeded(vdef)) {
       // TODO: copy of vdef as getter needed?
       // val getter = ValDef(mods, name, tpt, rhs) withPos vdef.pos?
       // right now vdef maps via expandedTree to a thicket which concerns itself.
@@ -173,7 +181,7 @@ object desugar {
       // The rhs gets filled in later, when field is generated and getter has parameters (see Memoize miniphase)
       val setterRhs = if (vdef.rhs.isEmpty) EmptyTree else unitLiteral
       val setter = cpy.DefDef(vdef)(
-        name     = name.setterName,
+        name     = valName.setterName,
         tparams  = Nil,
         vparamss = (setterParam :: Nil) :: Nil,
         tpt      = TypeTree(defn.UnitType),
@@ -887,7 +895,7 @@ object desugar {
           mdef.tparams.head.srcPos)
       defDef(
         cpy.DefDef(mdef)(
-          name = mdef.name.toExtensionName,
+          name = normalizeName(mdef, ext).toExtensionName,
           tparams = ext.tparams ++ mdef.tparams,
           vparamss = mdef.vparamss match
             case vparams1 :: vparamss1 if mdef.name.isRightAssocOperatorName =>
@@ -934,8 +942,13 @@ object desugar {
       report.error(IllegalRedefinitionOfStandardKind(kind, name), errPos)
       name = name.errorName
     }
-    if name.isExtensionName && (!mdef.mods.is(ExtensionMethod) || name.dropExtension.isExtensionName) then
-      report.error(em"illegal method name: $name may not start with `extension_`", errPos)
+    mdef match {
+      case vdef: ValDef if name.isExtension && isSetterNeeded(vdef)  =>
+        report.error(em"illegal setter name: `extension_=`", errPos)
+      case memDef if name.isExtensionName && !mdef.mods.is(ExtensionMethod) =>
+        report.error(em"illegal name: $name may not start with `extension_`", errPos)
+      case _ =>
+    }
     name
   }
 

compiler/src/dotty/tools/dotc/core/NameOps.scala

@@ -133,6 +133,12 @@ object NameOps {
       else name.toTermName
     }
 
+    /** Does the name match `extension`? */
+    def isExtension: Boolean = name match
+      case name: SimpleName =>
+        name.length == "extension".length && name.startsWith("extension")
+      case _ => false
+
     /** Does this name start with `extension_`? */
     def isExtensionName: Boolean = name match
       case name: SimpleName => name.startsWith("extension_")

tests/neg/illegal-extension.check

@@ -0,0 +1,20 @@
+-- Error: tests/neg/illegal-extension.scala:2:6 ------------------------------------------------------------------------
+2 |  def extension_n: String = "illegal method" // error: illegal name: extension_n may not start with `extension_`
+  |      ^^^^^^^^^^^
+  |      illegal name: extension_n may not start with `extension_`
+-- Error: tests/neg/illegal-extension.scala:4:6 ------------------------------------------------------------------------
+4 |  val extension_val = 23 // error: illegal name: extension_val may not start with `extension_`
+  |      ^^^^^^^^^^^^^
+  |      illegal name: extension_val may not start with `extension_`
+-- Error: tests/neg/illegal-extension.scala:5:14 -----------------------------------------------------------------------
+5 |  private var extension = Nil // error: illegal setter name: `extension_=`
+  |              ^^^^^^^^^
+  |              illegal setter name: `extension_=`
+-- Error: tests/neg/illegal-extension.scala:16:23 ----------------------------------------------------------------------
+16 |extension (x: Any) def extension_foo: String = "foo" // error: illegal name: extension_foo may not start with `extension_`
+   |                       ^^^^^^^^^^^^^
+   |                       illegal name: extension_foo may not start with `extension_`
+-- Error: tests/neg/illegal-extension.scala:9:6 ------------------------------------------------------------------------
+9 |  var extension = 1337 // error: illegal setter name: `extension_=`
+  |      ^^^^^^^^^
+  |      illegal setter name: `extension_=`

tests/neg/illegal-extension.scala

@@ -1,5 +1,20 @@
 trait A {
-  def extension_n: String = "illegal method" // error: illegal method name: extension_n may not start with `extension_`
+  def extension_n: String = "illegal method" // error: illegal name: extension_n may not start with `extension_`
+  type extension_type = Int // allowed because it's a type alias
+  val extension_val = 23 // error: illegal name: extension_val may not start with `extension_`
+  private var extension = Nil // error: illegal setter name: `extension_=`
 }
 
-extension (x: Any) def extension_foo: String = "foo" // error: illegal method name: extension_foo may not start with `extension_`
+class B {
+  var extension = 1337 // error: illegal setter name: `extension_=`
+}
+
+class C {
+  private var extension = "OK" // allowed because it does not require a setter
+}
+
+extension (x: Any) def extension_foo: String = "foo" // error: illegal name: extension_foo may not start with `extension_`
+extension (some: Any) def valid_extension_name: String = {
+  var extension = "foo" // `extension` name allowed because it doesn't require a setter
+  s"$extension bar"
+}