wip: neg/t6276.scala

vals no longer have rhs after fields,
so must check the assign node it was lifted out to

Author: adriaanm

src/compiler/scala/tools/nsc/typechecker/RefChecks.scala

@@ -1127,22 +1127,16 @@ abstract class RefChecks extends InfoTransform with scala.reflect.internal.trans
       case _ =>
     }
 
-    // SI-6276 warn for `def foo = foo` or `val bar: X = bar`, which come up more frequently than you might think.
-    def checkInfiniteLoop(valOrDef: ValOrDefDef) {
-      def callsSelf = valOrDef.rhs match {
-        case t @ (Ident(_) | Select(This(_), _)) =>
-          t hasSymbolWhich (_.accessedOrSelf == valOrDef.symbol)
-        case _ => false
+    // SI-6276 warn for trivial recursion, such as `def foo = foo` or `val bar: X = bar`, which come up more frequently than you might think.
+    // TODO: Move to abide rule. Also, this does not check that the def is final or not overridden, for example
+    def checkInfiniteLoop(sym: Symbol, rhs: Tree): Unit =
+      if (!sym.isValueParameter && sym.paramss.isEmpty) {
+        rhs match {
+          case t@(Ident(_) | Select(This(_), _)) if t hasSymbolWhich (_.accessedOrSelf == sym) =>
+            reporter.warning(rhs.pos, s"${sym.fullLocationString} does nothing other than call itself recursively")
+          case _ =>
+        }
       }
-      val trivialInfiniteLoop = (
-        !valOrDef.isErroneous
-     && !valOrDef.symbol.isValueParameter
-     && valOrDef.symbol.paramss.isEmpty
-     && callsSelf
-      )
-      if (trivialInfiniteLoop)
-        reporter.warning(valOrDef.rhs.pos, s"${valOrDef.symbol.fullLocationString} does nothing other than call itself recursively")
-    }
 
 // Transformation ------------------------------------------------------------
 
@@ -1621,9 +1615,18 @@ abstract class RefChecks extends InfoTransform with scala.reflect.internal.trans
             sym resetFlag DEFERRED
             transform(deriveDefDef(tree)(_ => typed(gen.mkSysErrorCall("native method stub"))))
 
-          case ValDef(_, _, _, _) | DefDef(_, _, _, _, _, _) =>
+          case Assign(tgt, rhs) =>
+            if (!tree.isErroneous)
+              checkInfiniteLoop(tgt.symbol, rhs)
+            tree
+
+          // NOTE: The fields phase has moved the RHS of ValDefs in classes to an initialization statement in the template.
+          case tree: ValOrDefDef =>
             checkDeprecatedOvers(tree)
-            checkInfiniteLoop(tree.asInstanceOf[ValOrDefDef])
+
+            if (!tree.isErroneous)
+              checkInfiniteLoop(tree.symbol, tree.rhs)
+
             if (settings.warnNullaryUnit)
               checkNullaryMethodReturnType(sym)
             if (settings.warnInaccessible) {