address review: move check to typer

Author: liufengyun

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

@@ -75,21 +75,6 @@ object RefChecks {
     }
   }
 
-  /** Check that a stable identifier pattern is indeed stable (SLS 8.1.5)
-   */
-  private def checkStableIdentPattern(tree: Tree)(implicit ctx: Context) = {
-    def error = ctx.error(s"stable identifier required, but ${tree.show} found", tree.pos)
-    tree match {
-      case _: Ident if !isWildcardArg(tree) =>
-        if (!tree.tpe.isStable) error
-      case _: Select =>
-        if (!tree.tpe.isStable) error
-      case _: Apply =>
-        error
-      case _ =>
-    }
-  }
-
   /** The this-type of `cls` which should be used when looking at the types of
    *  inherited members. If `cls` has a non-trivial self type, this returns a skolem
    *  with the class type instead of the `this-type` of the class as usual.
@@ -899,26 +884,6 @@ class RefChecks extends MiniPhase { thisPhase =>
     currentLevel.enterReference(sym, tree.pos)
     tree
   }
-
-  override def transformUnApply(tree: UnApply)(implicit ctx: Context): Tree = {
-    tree.patterns.foreach(checkStableIdentPattern(_))
-    tree
-  }
-
-  override def transformAlternative(tree: Alternative)(implicit ctx: Context): Tree = {
-    tree.trees.foreach(checkStableIdentPattern(_))
-    tree
-  }
-
-  override def transformBind(tree: Bind)(implicit ctx: Context): Tree = {
-     checkStableIdentPattern(tree.body)
-    tree
-  }
-
-  override def transformCaseDef(tree: CaseDef)(implicit ctx: Context) = {
-    checkStableIdentPattern(tree.pat)
-    tree
-  }
 }
 
 /* todo: rewrite and re-enable

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

@@ -406,9 +406,23 @@ class Typer extends Namer
         tree.withType(ownType)
     }
 
+    checkStableIdentPattern(tree1, pt)
     checkValue(tree1, pt)
   }
 
+  /** Check that a stable identifier pattern is indeed stable (SLS 8.1.5)
+   */
+  private def checkStableIdentPattern(tree: Tree, pt: Type)(implicit ctx: Context): Tree = {
+    if (ctx.mode.is(Mode.Pattern) &&
+        !tree.isType &&
+        !pt.isInstanceOf[ApplyingProto] &&
+        !tree.tpe.isStable &&
+        !isWildcardArg(tree))
+      ctx.error(s"stable identifier required, but ${tree.show} found", tree.pos)
+
+    tree
+  }
+
   private def typedSelect(tree: untpd.Select, pt: Type, qual: Tree)(implicit ctx: Context): Select =
     checkValue(assignType(cpy.Select(tree)(qual, tree.name), qual), pt)
 
@@ -418,7 +432,7 @@ class Typer extends Namer
       val qual1 = typedExpr(tree.qualifier, selectionProto(tree.name, pt, this))
       if (tree.name.isTypeName) checkStable(qual1.tpe, qual1.pos)
       val select = typedSelect(tree, pt, qual1)
-      if (select.tpe ne TryDynamicCallType) select
+      if (select.tpe ne TryDynamicCallType) checkStableIdentPattern(select, pt)
       else if (pt.isInstanceOf[PolyProto] || pt.isInstanceOf[FunProto] || pt == AssignProto) select
       else typedDynamicSelect(tree, Nil, pt)
     }