Merge pull request #15027 from nim-lang/araq-cursor-fix

cursor inference bugfix

compiler/cursor_inference.nim

@@ -237,10 +237,11 @@ proc analyse(c: var Con; n: PNode) =
       # assignments like 'x.field = value' mean that 'x' itself cannot
       # be a cursor:
       let r = locationRoot(n[0])
-      if r != nil and r.typ.skipTypes(abstractInst).kind notin {tyPtr, tyRef}:
+      if r != nil:
         # however, an assignment like 'it.field = x' does not influence r's
         # cursorness property:
-        c.mayOwnData.incl r.id
+        if r.typ.skipTypes(abstractInst).kind notin {tyPtr, tyRef}:
+          c.mayOwnData.incl r.id
         c.mutations.incl r.id
 
     if hasDestructor(n[1].typ):

tests/arc/topt_no_cursor.nim

@@ -1,6 +1,9 @@
 discard """
-  output: '''(repo: "", package: "meo", ext: "")'''
+  output: '''(repo: "", package: "meo", ext: "")
-  cmd: '''nim c --gc:arc --expandArc:newTarget --hint:Performance:off $file'''
+doing shady stuff...
+3
+6'''
+  cmd: '''nim c --gc:arc --expandArc:newTarget --expandArc:delete --hint:Performance:off $file'''
   nimout: '''--expandArc: newTarget
 
 var
@@ -23,6 +26,14 @@ result = (
   let blitTmp_2 = :tmp_2
   blitTmp_2)
 `=destroy`(splat)
+-- end of expandArc ------------------------
+--expandArc: delete
+
+var saved
+var sibling_cursor = target.parent.left
+`=`(saved, sibling_cursor.right)
+`=`(sibling_cursor.right, saved.left)
+`=sink`(sibling_cursor.parent, saved)
 -- end of expandArc ------------------------'''
 """
 
@@ -35,3 +46,52 @@ proc newTarget*(path: string): Target =
   result = (repo: splat.dir, package: splat.name, ext: splat.ext)
 
 echo newTarget("meo")
+
+type
+  Node = ref object
+    left, right, parent: Node
+    value: int
+
+proc delete(target: var Node) =
+  var sibling = target.parent.left # b3
+  var saved = sibling.right # b3.right -> r4
+
+  sibling.right = saved.left # b3.right -> r4.left = nil
+  sibling.parent = saved # b3.parent -> r5 = r4
+
+  #[after this proc:
+        b 5
+      /   \
+    b 3     b 6
+  ]#
+
+
+#[before:
+      r 5
+    /   \
+  b 3    b 6 - to delete
+  /    \
+empty  r 4
+]#
+proc main =
+  var five = Node(value: 5)
+
+  var six = Node(value: 6)
+  six.parent = five
+  five.right = six
+
+  var three = Node(value: 3)
+  three.parent = five
+  five.left = three
+
+  var four = Node(value: 4)
+  four.parent = three
+  three.right = four
+
+  echo "doing shady stuff..."
+  delete(six)
+  # need both of these echos
+  echo five.left.value
+  echo five.right.value
+
+main()