An unnamed break in a block now gives an UnnamedBreak warning (#20901)

* unnamed break in the block now gives an error

* bootstrap

* fixes

* more fixes

* break with label

* label again

* one moee

* Delete test5.txt

* it now gives a UnnamedBreak warning

* change the URL of bump back to the original one

tests/controlflow/tcontrolflow.nim

@@ -19,7 +19,7 @@ block tbreak:
     run = false
     block myblock:
       if true:
-        break
+        break myblock
       echo "leaving myblock"
     x = true
   doAssert(x)
@@ -95,3 +95,22 @@ block tnestif:
   else:
       writeLine(stdout, "looks like Python")
   #OUT i == 2
+
+# bug https://github.com/nim-lang/RFCs/issues/451
+for i in 1..2: # works
+  break
+
+block: # works
+  for i in 1..2:
+    break
+
+block: # works
+  block:
+    discard 12 + 3
+  for i in 1..2:
+    break
+
+block named: # works
+  if true:
+    break named
+  doAssert false, "not reached"

tests/controlflow/tunamedbreak.nim

@@ -0,0 +1,15 @@
+
+discard """
+  cmd: "nim check $file"
+  action: "reject"
+  nimout: '''
+tunamedbreak.nim(12, 5) Error: Using an unnamed break in a block is deprecated; Use a named block with a named break instead [UnnamedBreak]
+tunamedbreak.nim(15, 3) Error: Using an unnamed break in a block is deprecated; Use a named block with a named break instead [UnnamedBreak]
+  '''
+"""
+for i in 1..2: # errors
+  block:
+    break
+
+block: # errors
+  break