fixes #24793; Revert "remove special treatments of sinking const sequences (#24812)

fixes #24793

There doesn't seem to have a better solution

Author: ringabout

compiler/injectdestructors.nim

@@ -493,6 +493,25 @@ proc passCopyToSink(n: PNode; c: var Con; s: var Scope): PNode =
   # no need to destroy it.
   result.add tmp
 
+proc isDangerousSeq(t: PType): bool {.inline.} =
+  let t = t.skipTypes(abstractInst)
+  result = t.kind == tySequence and tfHasOwned notin t.elementType.flags
+
+proc containsConstSeq(n: PNode): bool =
+  if n.kind == nkBracket and n.len > 0 and n.typ != nil and isDangerousSeq(n.typ):
+    return true
+  result = false
+  case n.kind
+  of nkExprEqExpr, nkExprColonExpr, nkHiddenStdConv, nkHiddenSubConv, nkCast:
+    result = containsConstSeq(n[1])
+  of nkObjConstr, nkClosure:
+    for i in 1..<n.len:
+      if containsConstSeq(n[i]): return true
+  of nkCurly, nkBracket, nkPar, nkTupleConstr:
+    for son in n:
+      if containsConstSeq(son): return true
+  else: discard
+
 proc ensureDestruction(arg, orig: PNode; c: var Con; s: var Scope): PNode =
   # it can happen that we need to destroy expression contructors
   # like [], (), closures explicitly in order to not leak them.
@@ -776,7 +795,12 @@ proc p(n: PNode; c: var Con; s: var Scope; mode: ProcessMode; tmpFlags = {sfSing
     template process(child, s): untyped = p(child, c, s, mode)
     handleNestedTempl(n, process, tmpFlags = tmpFlags)
   elif mode == sinkArg:
-    if n.kind in {nkBracket, nkObjConstr, nkTupleConstr, nkClosure, nkNilLit} +
+    if n.containsConstSeq:
+      # const sequences are not mutable and so we need to pass a copy to the
+      # sink parameter (bug #11524). Note that the string implementation is
+      # different and can deal with 'const string sunk into var'.
+      result = passCopyToSink(n, c, s)
+    elif n.kind in {nkBracket, nkObjConstr, nkTupleConstr, nkClosure, nkNilLit} +
          nkCallKinds + nkLiterals:
       result = p(n, c, s, consumed)
     elif ((n.kind == nkSym and isSinkParam(n.sym)) or isAnalysableFieldAccess(n, c.owner)) and
@@ -1143,7 +1167,17 @@ proc moveOrCopy(dest, ri: PNode; c: var Con; s: var Scope, flags: set[MoveOrCopy
         dec c.inEnsureMove, isEnsureMove
         result.add p(ri, c, s, consumed)
         c.finishCopy(result, dest, flags, isFromSink = false)
-    of nkBracket, nkObjConstr, nkTupleConstr, nkClosure, nkCharLit..nkNilLit:
+    of nkBracket:
+      # array constructor
+      if ri.len > 0 and isDangerousSeq(ri.typ):
+        inc c.inEnsureMove, isEnsureMove
+        result = c.genCopy(dest, ri, flags)
+        dec c.inEnsureMove, isEnsureMove
+        result.add p(ri, c, s, consumed)
+        c.finishCopy(result, dest, flags, isFromSink = false)
+      else:
+        result = c.genSink(s, dest, p(ri, c, s, consumed), flags)
+    of nkObjConstr, nkTupleConstr, nkClosure, nkCharLit..nkNilLit:
       result = c.genSink(s, dest, p(ri, c, s, consumed), flags)
     of nkSym:
       if isSinkParam(ri.sym) and isLastRead(ri, c, s):

tests/objects/tobject_default_value.nim

@@ -811,3 +811,11 @@ template main {.dirty.} =
 
 static: main()
 main()
+
+block:
+  type
+    MyTyp = ref object
+      thing = initTable[string,string]()
+
+  var t = MyTyp()
+  t.thing[""] = ""