no ropes WIP (#20433)

* refactorings in preparation for ropes elimination of the C code generator; mostly the usual ': Rope' -> 'result: var Rope' rewrite
* rewrote ccgcalls.nim
* refactored ccgexprs.nim
* ccgliterals: refactoring
* refactoring: code dealing with name mangling
* refactoring: getRecordFieldsAux
* ropes are strings (insert obscene joke here)
* optimize JS code gen
* optimizations and code improvements
* more optimizations
* final cleanups

compiler/astalgo.nim

@@ -12,9 +12,11 @@
 # the data structures here are used in various places of the compiler.
 
 import
-  ast, hashes, intsets, strutils, options, lineinfos, ropes, idents, rodutils,
+  ast, hashes, intsets, options, lineinfos, ropes, idents, rodutils,
   msgs
 
+import strutils except addf
+
 when defined(nimPreviewSlimSystem):
   import std/assertions
 
@@ -258,7 +260,7 @@ proc makeYamlString*(s: string): Rope =
   # this could trigger InternalError(111). See the ropes module for
   # further information.
   const MaxLineLength = 64
-  result = nil
+  result = ""
   var res = "\""
   for i in 0..<s.len:
     if (i + 1) mod MaxLineLength == 0:
@@ -274,9 +276,9 @@ proc flagsToStr[T](flags: set[T]): Rope =
   if flags == {}:
     result = rope("[]")
   else:
-    result = nil
+    result = ""
     for x in items(flags):
-      if result != nil: result.add(", ")
+      if result != "": result.add(", ")
       result.add(makeYamlString($x))
     result = "[" & result & "]"