fixes #5417

compiler/ccgstmts.nim

@@ -540,7 +540,7 @@ proc genBreakStmt(p: BProc, t: PNode) =
     # named break?
     assert(t.sons[0].kind == nkSym)
     var sym = t.sons[0].sym
-    assert(sym.loc.k == locOther)
+    doAssert(sym.loc.k == locOther)
     idx = sym.position-1
   else:
     # an unnamed 'break' can only break a loop after 'transf' pass:

compiler/semstmts.nim

@@ -30,6 +30,7 @@ proc semBreakOrContinue(c: PContext, n: PNode): PNode =
       of nkIdent: s = lookUp(c, n.sons[0])
       of nkSym: s = n.sons[0].sym
       else: illFormedAst(n)
+      s = getGenSym(c, s)
       if s.kind == skLabel and s.owner.id == c.p.owner.id:
         var x = newSymNode(s)
         x.info = n.info

compiler/semtempl.nim

@@ -384,6 +384,8 @@ proc semTemplBody(c: var TemplCtx, n: PNode): PNode =
     checkSonsLen(n, 2)
     openScope(c)
     if n.sons[0].kind != nkEmpty:
+      addLocalDecl(c, n.sons[0], skLabel)
+      when false:
         # labels are always 'gensym'ed:
         let s = newGenSym(skLabel, n.sons[0], c)
         addPrelimDecl(c.c, s)

tests/template/tgensym_label.nim

@@ -0,0 +1,18 @@
+
+# bug #5417
+import macros
+
+macro genBody: untyped =
+  let sbx = genSym(nskLabel, "test")
+  when true:
+    result = quote do:
+      block `sbx`:
+        break `sbx`
+  else:
+    template foo(s1, s2) =
+      block s1:
+        break s2
+    result = getAst foo(sbx, sbx)
+
+proc test() =
+  genBody()