fix #13011, error out infinite recursive lazy val

Co-authored-by: Tom Grigg <griggt@users.noreply.github.com>
Co-authored-by: Nicolas Stucki <nicolasstucki@users.noreply.github.com>
Co-authored-by: Timothée Andres <timothee.andres@epfl.ch>

Author: 4 people

compiler/src/dotty/tools/dotc/transform/CheckLoopingImplicits.scala

@@ -20,7 +20,13 @@ class CheckLoopingImplicits extends MiniPhase:
 
   override def phaseName: String = CheckLoopingImplicits.name
 
-  override def transformDefDef(mdef: DefDef)(using Context): DefDef =
+  override def transformValDef(mdef: ValDef)(using Context): Tree = 
+    transform(mdef)
+
+  override def transformDefDef(mdef: DefDef)(using Context): Tree =
+    transform(mdef)
+
+  def transform(mdef: ValOrDefDef)(using Context): Tree =
     val sym = mdef.symbol
 
     def checkNotSelfRef(t: RefTree) =
@@ -70,12 +76,12 @@ class CheckLoopingImplicits extends MiniPhase:
         checkNotLooping(finalizer)
       case SeqLiteral(elems, _) =>
         elems.foreach(checkNotLooping)
-      case t: ValDef =>
-        if !t.symbol.is(Lazy) then checkNotLooping(t.rhs)
+      case t: ValDef =>  
+        checkNotLooping(t.rhs)
       case _ =>
 
-    if sym.isOneOf(GivenOrImplicit) then
+    if sym.isOneOf(GivenOrImplicit | Lazy) then
       checkNotLooping(mdef.rhs)
     mdef
-  end transformDefDef
+  end transform
 end CheckLoopingImplicits

tests/neg-custom-args/fatal-warnings/i13542.scala

@@ -40,7 +40,7 @@ val x5 =
 
 val x6 =
   implicit def barToFoo4(bar: Bar): Foo =
-    lazy val y = bar.toFoo  // OK
+    lazy val y = bar.toFoo  // error
     if false then y else ???
   val foo: Foo = Bar(1)
 

tests/neg/i13011.scala

@@ -0,0 +1,17 @@
+class i13011 {
+  lazy implicit val simple1: String = simple1 // error
+  def f: Unit = {
+    lazy val simple2: String = simple2 // error
+  }
+
+  lazy val simple3: String = if true then this.simple3 else "a" // error
+
+  lazy val simple4: String = identity(this.simple4) // error
+        
+  lazy val simple5: String = {  // error
+    this.simple5
+    "aa"
+  }
+
+  lazy val simple6: Function0[Any] = () => this.simple6  // Ok
+}