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

compiler/condsyms.nim

@@ -148,3 +148,4 @@ proc initDefines*(symbols: StringTableRef) =
 
   defineSymbol("nimHasOutParams")
   defineSymbol("nimHasSystemRaisesDefect")
+  defineSymbol("nimHasWarnUnnamedBreak")

compiler/lineinfos.nim

@@ -84,6 +84,7 @@ type
     warnEffect = "Effect",
     warnCastSizes = "CastSizes"
     warnTemplateRedefinition = "TemplateRedefinition",
+    warnUnnamedBreak = "UnnamedBreak",
     warnUser = "User",
     # hints
     hintSuccess = "Success", hintSuccessX = "SuccessX",
@@ -181,6 +182,7 @@ const
     warnEffect: "$1",
     warnCastSizes: "$1",
     warnTemplateRedefinition: "template '$1' is implicitly redefined, consider adding an explicit .redefine pragma",
+    warnUnnamedBreak: "Using an unnamed break in a block is deprecated; Use a named block with a named break instead",
     warnUser: "$1",
     hintSuccess: "operation successful: $#",
     # keep in sync with `testament.isSuccess`

compiler/nim.cfg

@@ -27,9 +27,13 @@ define:useStdoutAsStdmsg
 #gc:markAndSweep
 
 @if nimHasWarningObservableStores:
-  warning[ObservableStores]: off
+  warning[ObservableStores]:off
 @end
 
 @if nimHasWarningAsError:
-  warningAsError:GcUnsafe2:on
+  warningAsError[GcUnsafe2]:on
+@end
+
+@if nimHasWarnUnnamedBreak:
+  warningAserror[UnnamedBreak]:on
 @end

compiler/semdata.nim

@@ -38,6 +38,7 @@ type
     resultSym*: PSym          # the result symbol (if we are in a proc)
     nestedLoopCounter*: int   # whether we are in a loop or not
     nestedBlockCounter*: int  # whether we are in a block or not
+    breakInLoop*: bool        # whether we are in a loop without block
     next*: PProcCon           # used for stacking procedure contexts
     mappingExists*: bool
     mapping*: TIdTable

compiler/semexprs.nim

@@ -2640,6 +2640,8 @@ include semobjconstr
 proc semBlock(c: PContext, n: PNode; flags: TExprFlags; expectedType: PType = nil): PNode =
   result = n
   inc(c.p.nestedBlockCounter)
+  let oldBreakInLoop = c.p.breakInLoop
+  c.p.breakInLoop = false
   checkSonsLen(n, 2, c.config)
   openScope(c) # BUGFIX: label is in the scope of block!
   if n[0].kind != nkEmpty:
@@ -2657,6 +2659,7 @@ proc semBlock(c: PContext, n: PNode; flags: TExprFlags; expectedType: PType = ni
   if isEmptyType(n.typ): n.transitionSonsKind(nkBlockStmt)
   else: n.transitionSonsKind(nkBlockExpr)
   closeScope(c)
+  c.p.breakInLoop = oldBreakInLoop
   dec(c.p.nestedBlockCounter)
 
 proc semExportExcept(c: PContext, n: PNode): PNode =

compiler/semfields.nim

@@ -133,6 +133,8 @@ proc semForFields(c: PContext, n: PNode, m: TMagic): PNode =
       typeMismatch(c.config, calli.info, tupleTypeA, tupleTypeB, calli)
 
   inc(c.p.nestedLoopCounter)
+  let oldBreakInLoop = c.p.breakInLoop
+  c.p.breakInLoop = true
   if tupleTypeA.kind == tyTuple:
     var loopBody = n[^1]
     for i in 0..<tupleTypeA.len:
@@ -156,6 +158,7 @@ proc semForFields(c: PContext, n: PNode, m: TMagic): PNode =
       semForObjectFields(fc, t.n, n, stmts)
       if t[0] == nil: break
       t = skipTypes(t[0], skipPtrs)
+  c.p.breakInLoop = oldBreakInLoop
   dec(c.p.nestedLoopCounter)
   # for TR macros this 'while true: ...; break' loop is pretty bad, so
   # we avoid it now if we can:

compiler/semstmts.nim

@@ -73,6 +73,8 @@ proc semBreakOrContinue(c: PContext, n: PNode): PNode =
         localError(c.config, n.info, errInvalidControlFlowX % s.name.s)
     else:
       localError(c.config, n.info, errGenerated, "'continue' cannot have a label")
+  elif c.p.nestedBlockCounter > 0 and n.kind == nkBreakStmt and not c.p.breakInLoop:
+    localError(c.config, n.info, warnUnnamedBreak)
   elif (c.p.nestedLoopCounter <= 0) and ((c.p.nestedBlockCounter <= 0) or n.kind == nkContinueStmt):
     localError(c.config, n.info, errInvalidControlFlowX %
                renderTree(n, {renderNoComments}))
@@ -89,7 +91,10 @@ proc semWhile(c: PContext, n: PNode; flags: TExprFlags): PNode =
   openScope(c)
   n[0] = forceBool(c, semExprWithType(c, n[0], expectedType = getSysType(c.graph, n.info, tyBool)))
   inc(c.p.nestedLoopCounter)
+  let oldBreakInLoop = c.p.breakInLoop
+  c.p.breakInLoop = true
   n[1] = semStmt(c, n[1], flags)
+  c.p.breakInLoop = oldBreakInLoop
   dec(c.p.nestedLoopCounter)
   closeScope(c)
   if n[1].typ == c.enforceVoidContext:
@@ -959,11 +964,14 @@ proc semForVars(c: PContext, n: PNode; flags: TExprFlags): PNode =
           if not isDiscardUnderscore(v): addDecl(c, v)
         elif v.owner == nil: v.owner = getCurrOwner(c)
   inc(c.p.nestedLoopCounter)
+  let oldBreakInLoop = c.p.breakInLoop
+  c.p.breakInLoop = true
   openScope(c)
   n[^1] = semExprBranch(c, n[^1], flags)
   if efInTypeof notin flags:
     discardCheck(c, n[^1], flags)
   closeScope(c)
+  c.p.breakInLoop = oldBreakInLoop
   dec(c.p.nestedLoopCounter)
 
 proc implicitIterator(c: PContext, it: string, arg: PNode): PNode =

compiler/semtypes.nim

@@ -1457,6 +1457,8 @@ proc semStmtListType(c: PContext, n: PNode, prev: PType): PType =
 
 proc semBlockType(c: PContext, n: PNode, prev: PType): PType =
   inc(c.p.nestedBlockCounter)
+  let oldBreakInLoop = c.p.breakInLoop
+  c.p.breakInLoop = false
   checkSonsLen(n, 2, c.config)
   openScope(c)
   if n[0].kind notin {nkEmpty, nkSym}:
@@ -1465,6 +1467,7 @@ proc semBlockType(c: PContext, n: PNode, prev: PType): PType =
   n[1].typ = result
   n.typ = result
   closeScope(c)
+  c.p.breakInLoop = oldBreakInLoop
   dec(c.p.nestedBlockCounter)
 
 proc semGenericParamInInvocation(c: PContext, n: PNode): PType =