Cosmetic compiler cleanup (#12718)

* Cleanup compiler code base

* Unify add calls

* Unify len invocations

* Unify range operators

* Fix oversight

* Remove {.procvar.} pragma

* initCandidate -> newCandidate where reasonable

* Unify safeLen calls

compiler/rodimpl.nim

@@ -156,31 +156,31 @@ proc encodeNode(g: ModuleGraph; fInfo: TLineInfo, n: PNode,
     encodeVInt(n.sym.id, result)
     pushSym(w, n.sym)
   else:
-    for i in 0 ..< len(n):
-      encodeNode(g, n.info, n.sons[i], result)
-  add(result, ')')
+    for i in 0..<n.len:
+      encodeNode(g, n.info, n[i], result)
+  result.add(')')
 
 proc encodeLoc(g: ModuleGraph; loc: TLoc, result: var string) =
   var oldLen = result.len
   result.add('<')
   if loc.k != low(loc.k): encodeVInt(ord(loc.k), result)
   if loc.storage != low(loc.storage):
-    add(result, '*')
+    result.add('*')
     encodeVInt(ord(loc.storage), result)
   if loc.flags != {}:
-    add(result, '$')
+    result.add('$')
     encodeVInt(cast[int32](loc.flags), result)
   if loc.lode != nil:
-    add(result, '^')
+    result.add('^')
     encodeNode(g, unknownLineInfo(), loc.lode, result)
   if loc.r != nil:
-    add(result, '!')
+    result.add('!')
     encodeStr($loc.r, result)
   if oldLen + 1 == result.len:
     # no data was necessary, so remove the '<' again:
     setLen(result, oldLen)
   else:
-    add(result, '>')
+    result.add('>')
 
 proc encodeType(g: ModuleGraph, t: PType, result: var string) =
   if t == nil:
@@ -191,73 +191,73 @@ proc encodeType(g: ModuleGraph, t: PType, result: var string) =
   if t.kind == tyForward: internalError(g.config, "encodeType: tyForward")
   # for the new rodfile viewer we use a preceding [ so that the data section
   # can easily be disambiguated:
-  add(result, '[')
+  result.add('[')
   encodeVInt(ord(t.kind), result)
-  add(result, '+')
+  result.add('+')
   encodeVInt(t.uniqueId, result)
   if t.id != t.uniqueId:
-    add(result, '+')
+    result.add('+')
     encodeVInt(t.id, result)
   if t.n != nil:
     encodeNode(g, unknownLineInfo(), t.n, result)
   if t.flags != {}:
-    add(result, '$')
+    result.add('$')
     encodeVInt(cast[int32](t.flags), result)
   if t.callConv != low(t.callConv):
-    add(result, '?')
+    result.add('?')
     encodeVInt(ord(t.callConv), result)
   if t.owner != nil:
-    add(result, '*')
+    result.add('*')
     encodeVInt(t.owner.id, result)
     pushSym(w, t.owner)
   if t.sym != nil:
-    add(result, '&')
+    result.add('&')
     encodeVInt(t.sym.id, result)
     pushSym(w, t.sym)
   if t.size != - 1:
-    add(result, '/')
+    result.add('/')
     encodeVBiggestInt(t.size, result)
   if t.align != 2:
-    add(result, '=')
+    result.add('=')
     encodeVInt(t.align, result)
   if t.lockLevel.ord != UnspecifiedLockLevel.ord:
-    add(result, '\14')
+    result.add('\14')
     encodeVInt(t.lockLevel.int16, result)
   if t.paddingAtEnd != 0:
-    add(result, '\15')
+    result.add('\15')
     encodeVInt(t.paddingAtEnd, result)
   for a in t.attachedOps:
-    add(result, '\16')
+    result.add('\16')
     if a == nil:
       encodeVInt(-1, result)
     else:
       encodeVInt(a.id, result)
       pushSym(w, a)
   for i, s in items(t.methods):
-    add(result, '\19')
+    result.add('\19')
     encodeVInt(i, result)
-    add(result, '\20')
+    result.add('\20')
     encodeVInt(s.id, result)
     pushSym(w, s)
   encodeLoc(g, t.loc, result)
   if t.typeInst != nil:
-    add(result, '\21')
+    result.add('\21')
     encodeVInt(t.typeInst.uniqueId, result)
     pushType(w, t.typeInst)
-  for i in 0 ..< len(t):
-    if t.sons[i] == nil:
-      add(result, "^()")
+  for i in 0..<t.len:
+    if t[i] == nil:
+      result.add("^()")
     else:
-      add(result, '^')
-      encodeVInt(t.sons[i].uniqueId, result)
-      pushType(w, t.sons[i])
+      result.add('^')
+      encodeVInt(t[i].uniqueId, result)
+      pushType(w, t[i])
 
 proc encodeLib(g: ModuleGraph, lib: PLib, info: TLineInfo, result: var string) =
-  add(result, '|')
+  result.add('|')
   encodeVInt(ord(lib.kind), result)
-  add(result, '|')
+  result.add('|')
   encodeStr($lib.name, result)
-  add(result, '|')
+  result.add('|')
   encodeNode(g, info, lib.path, result)
 
 proc encodeInstantiations(g: ModuleGraph; s: seq[PInstantiation];
@@ -316,7 +316,7 @@ proc encodeSym(g: ModuleGraph, s: PSym, result: var string) =
   encodeLoc(g, s.loc, result)
   if s.annex != nil: encodeLib(g, s.annex, s.info, result)
   if s.constraint != nil:
-    add(result, '#')
+    result.add('#')
     encodeNode(g, unknownLineInfo(), s.constraint, result)
   case s.kind
   of skType, skGenericParam: