constructor now uses result instead of this (#22724)

compiler/cgen.nim

@@ -1191,12 +1191,8 @@ proc genProcAux*(m: BModule, prc: PSym) =
  initLocalVar(p, res, immediateAsgn=false)
  returnStmt = ropecg(p.module, "\treturn $1;$n", [rdLoc(res.loc)])
  elif sfConstructor in prc.flags:
+ resNode.sym.loc.flags.incl lfIndirect
  fillLoc(resNode.sym.loc, locParam, resNode, "this", OnHeap)
- let ty = resNode.sym.typ[0] #generate nim's ctor
- for i in 1..<resNode.sym.ast.len:
- let field = resNode.sym.ast[i]
- genFieldObjConstr(p, ty, useTemp = false, isRef = false, 
- field[0], field[1], check = nil, resNode.sym.loc, "(*this)", tmpInfo)
  else:
  fillResult(p.config, resNode, prc.typ)
  assignParam(p, res, prc.typ[0])

compiler/semstmts.nim

@@ -1702,21 +1702,6 @@ proc swapResult(n: PNode, sRes: PSym, dNode: PNode) =
  n[i] = dNode
  swapResult(n[i], sRes, dNode)
 
-
-proc addThis(c: PContext, n: PNode, t: PType, owner: TSymKind) =
- var s = newSym(skResult, getIdent(c.cache, "this"), c.idgen,
- getCurrOwner(c), n.info)
- s.typ = t
- incl(s.flags, sfUsed)
- c.p.resultSym = s
- n.add newSymNode(c.p.resultSym)
- addParamOrResult(c, c.p.resultSym, owner)
- #resolves nim's obj ctor inside cpp ctors see #22669
- var typAst = t[0].sym.ast[0]
- if typAst.kind == nkPragmaExpr:
- typAst = typAst[0]
- s.ast = c.semExpr(c, newTree(nkCall, typAst))
-
 proc addResult(c: PContext, n: PNode, t: PType, owner: TSymKind) =
  template genResSym(s) =
  var s = newSym(skResult, getIdent(c.cache, "result"), c.idgen,
@@ -2373,19 +2358,14 @@ proc semProcAux(c: PContext, n: PNode, kind: TSymKind,
  # Macros and Templates can have generic parameters, but they are only
  # used for overload resolution (there is no instantiation of the symbol)
  if s.kind notin {skMacro, skTemplate} and s.magic == mNone: paramsTypeCheck(c, s.typ)
- var resultType: PType
- if {sfConstructor, sfImportc} * s.flags == {sfConstructor}:
- resultType = makePtrType(c, s.typ[0])
- addThis(c, n, resultType, skProc)
- else:
- maybeAddResult(c, s, n)
- resultType =
- if s.kind == skMacro:
- sysTypeFromName(c.graph, n.info, "NimNode")
- elif not isInlineIterator(s.typ):
- s.typ[0]
- else:
- nil
+ maybeAddResult(c, s, n)
+ let resultType =
+ if s.kind == skMacro:
+ sysTypeFromName(c.graph, n.info, "NimNode")
+ elif not isInlineIterator(s.typ):
+ s.typ[0]
+ else:
+ nil
  # semantic checking also needed with importc in case used in VM
  s.ast[bodyPos] = hloBody(c, semProcBody(c, n[bodyPos], resultType))
  # unfortunately we cannot skip this step when in 'system.compiles'

tests/cpp/tconstructor.nim

@@ -46,7 +46,7 @@ type NimClassNoNarent* = object
  x: int32
 
 proc makeNimClassNoParent(x:int32): NimClassNoNarent {. constructor.} =
- this.x = x
+ result.x = x
  discard
 
 let nimClassNoParent = makeNimClassNoParent(1)
@@ -58,11 +58,11 @@ var nimClassNoParentDef {.used.}: NimClassNoNarent #test has a default construc
 type NimClass* = object of CppClass
 
 proc makeNimClass(x:int32): NimClass {. constructor:"NimClass('1 #1) : CppClass(0, #1) ".} =
- this.x = x
+ result.x = x
 
 #optinially define the default constructor so we get rid of the cpp warn and we can declare the obj (note: default constructor of 'tyObject_NimClass__apRyyO8cfRsZtsldq1rjKA' is implicitly deleted because base class 'CppClass' has no default constructor)
 proc makeCppClass(): NimClass {. constructor: "NimClass() : CppClass(0, 0) ".} = 
- this.x = 1
+ result.x = 1
 
 let nimClass = makeNimClass(1)
 var nimClassDef {.used.}: NimClass #since we explictly defined the default constructor we can declare the obj
@@ -95,7 +95,7 @@ type
  else: discard
 
 proc makeNimClassWithDefault(): NimClassWithDefault {.constructor.} =
- discard
+ result = NimClassWithDefault()
 
 proc init =
  for i in 0 .. 1: