fixes #15884 (#18230)

* fixes #15884

* micro optimization

compiler/renderer.nim

@@ -1238,6 +1238,8 @@ proc gsub(g: var TSrcGen, n: PNode, c: TContext, fromStmtList = false) =
     putWithSpace(g, tkBind, "bind")
     gsub(g, n, 0)
   of nkCheckedFieldExpr, nkHiddenAddr, nkHiddenDeref, nkStringToCString, nkCStringToString:
+    if renderIds in g.flags:
+      putWithSpace(g, tkAddr, $n.kind)
     gsub(g, n, 0)
   of nkLambda:
     putWithSpace(g, tkProc, "proc")

compiler/sem.nim

@@ -100,6 +100,15 @@ proc fitNode(c: PContext, formal: PType, arg: PNode; info: TLineInfo): PNode =
     else:
       result = fitNodePostMatch(c, formal, result)
 
+proc fitNodeForLocalVar(c: PContext, formal: PType, arg: PNode; info: TLineInfo): PNode =
+  let a = fitNode(c, formal, arg, info)
+  if formal.kind in {tyVar, tyLent}:
+    #classifyViewType(formal) != noView:
+    result = newNodeIT(nkHiddenAddr, a.info, formal)
+    result.add a
+  else:
+   result = a
+
 proc inferWithMetatype(c: PContext, formal: PType,
                        arg: PNode, coerceDistincts = false): PNode
 

compiler/semexprs.nim

@@ -1643,7 +1643,7 @@ proc takeImplicitAddr(c: PContext, n: PNode; isLent: bool): PNode =
 proc asgnToResultVar(c: PContext, n, le, ri: PNode) {.inline.} =
   if le.kind == nkHiddenDeref:
     var x = le[0]
-    if (x.typ.kind in {tyVar, tyLent} or classifyViewType(x.typ) != noView) and x.kind == nkSym and x.sym.kind == skResult:
+    if x.kind == nkSym and x.sym.kind == skResult and (x.typ.kind in {tyVar, tyLent} or classifyViewType(x.typ) != noView):
       n[0] = x # 'result[]' --> 'result'
       n[1] = takeImplicitAddr(c, ri, x.typ.kind == tyLent)
       x.typ.flags.incl tfVarIsPtr

compiler/semstmts.nim

@@ -526,7 +526,7 @@ proc semVarOrLet(c: PContext, n: PNode, symkind: TSymKind): PNode =
         else:
           # BUGFIX: ``fitNode`` is needed here!
           # check type compatibility between def.typ and typ
-          def = fitNode(c, typ, def, def.info)
+          def = fitNodeForLocalVar(c, typ, def, def.info)
           #changeType(def.skipConv, typ, check=true)
       else:
         typ = def.typ.skipTypes({tyStatic, tySink}).skipIntLit(c.idgen)

compiler/varpartitions.nim

@@ -519,13 +519,17 @@ const
 proc isConstSym(s: PSym): bool =
   result = s.kind in {skConst, skLet} or isConstParam(s)
 
+proc toString(n: PNode): string =
+  if n.kind == nkEmpty: result = "<empty>"
+  else: result = $n
+
 proc borrowFrom(c: var Partitions; dest: PSym; src: PNode) =
   const
     url = "see https://nim-lang.github.io/Nim/manual_experimental.html#view-types-algorithm-path-expressions for details"
 
   let s = pathExpr(src, c.owner)
   if s == nil:
-    localError(c.g.config, src.info, "cannot borrow from " & $src & ", it is not a path expression; " & url)
+    localError(c.g.config, src.info, "cannot borrow from " & src.toString & ", it is not a path expression; " & url)
   elif s.kind == nkSym:
     if dest.kind == skResult:
       if s.sym.kind != skParam or s.sym.position != 0: