Fix renderer's errors (#7742)

* Fix renderer's errors

* Same for filter_tmpl

* var -> let

compiler/filter_tmpl.nim

@@ -42,7 +42,8 @@ proc newLine(p: var TTmplParser) =
 
 proc scanPar(p: var TTmplParser, d: int) =
   var i = d
-  while true:
+  let hi = p.x.len - 1
+  while i <= hi:
     case p.x[i]
     of '\0': break
     of '(': inc(p.par)

compiler/renderer.nim

@@ -175,10 +175,11 @@ proc put(g: var TSrcGen, kind: TTokType, s: string) =
 proc putComment(g: var TSrcGen, s: string) =
   if s.isNil: return
   var i = 0
+  let hi = len(s) - 1
   var isCode = (len(s) >= 2) and (s[1] != ' ')
   var ind = g.lineLen
   var com = "## "
-  while true:
+  while i <= hi:
     case s[i]
     of '\0':
       break
@@ -201,12 +202,12 @@ proc putComment(g: var TSrcGen, s: string) =
       # gets too long:
       # compute length of the following word:
       var j = i
-      while s[j] > ' ': inc(j)
+      while j <= hi and s[j] > ' ': inc(j)
       if not isCode and (g.lineLen + (j - i) > MaxLineLen):
         put(g, tkComment, com)
         optNL(g, ind)
         com = "## "
-      while s[i] > ' ':
+      while i <= hi and s[i] > ' ':
         add(com, s[i])
         inc(i)
   put(g, tkComment, com)
@@ -215,8 +216,9 @@ proc putComment(g: var TSrcGen, s: string) =
 proc maxLineLength(s: string): int =
   if s.isNil: return 0
   var i = 0
+  let hi = len(s) - 1
   var lineLen = 0
-  while true:
+  while i <= hi:
     case s[i]
     of '\0':
       break
@@ -235,7 +237,7 @@ proc maxLineLength(s: string): int =
 
 proc putRawStr(g: var TSrcGen, kind: TTokType, s: string) =
   var i = 0
-  var hi = len(s) - 1
+  let hi = len(s) - 1
   var str = ""
   while i <= hi:
     case s[i]