fixes: replace ensureMutable with backendEnsureMutable in ccgtypes (#25640)

compiler/ccgtypes.nim

@@ -309,7 +309,7 @@ proc addAbiCheck(m: BModule; t: PType, name: Rope) =
 
 
 proc fillResult(conf: ConfigRef; param: PNode, proctype: PType) =
-  ensureMutable param.sym
+  backendEnsureMutable param.sym
   fillLoc(param.sym.locImpl, locParam, param, "Result",
           OnStack)
   let t = param.sym.typ
@@ -542,7 +542,7 @@ proc genMemberProcParams(m: BModule; prc: PSym, superCall, rettype, name, params
   var types, names, args: seq[string] = @[]
   if not isCtor:
     var this = t.n[1].sym
-    ensureMutable this
+    backendEnsureMutable this
     fillParamName(m, this)
     fillLoc(this.locImpl, locParam, t.n[1],
             this.paramStorageLoc)
@@ -564,7 +564,7 @@ proc genMemberProcParams(m: BModule; prc: PSym, superCall, rettype, name, params
       else:
         descKind = dkRefParam
     var typ, name: string
-    ensureMutable param
+    backendEnsureMutable param
     fillParamName(m, param)
     fillLoc(param.locImpl, locParam, t.n[i],
             param.paramStorageLoc)
@@ -1183,7 +1183,7 @@ proc genMemberProcHeader(m: BModule; prc: PSym; result: var Builder; asPtr: bool
   let isCtor = sfConstructor in prc.flags
   var check = initIntSet()
   fillBackendName(m, prc)
-  ensureMutable prc
+  backendEnsureMutable prc
   fillLoc(prc.locImpl, locProc, prc.ast[namePos], OnUnknown)
   var memberOp = "#." #only virtual
   var typ: PType

tests/ic/tmiscs.nim

@@ -4,6 +4,8 @@ discard """
 5
 3
 2
+1.0
+2.0
 '''
 """
 
@@ -42,4 +44,26 @@ proc divmod(a, b: int): (int, int) =
 
 let (q, r) = divmod(17, 5)
 echo q
-echo r
+echo r
+
+
+# Shallow object with seq (trigger GC interaction)
+type
+  Matrix = object
+    rows, cols: int
+    data: seq[float]
+
+proc newMatrix(r, c: int): Matrix =
+  Matrix(rows: r, cols: c, data: newSeq[float](r * c))
+
+proc `[]`(m: Matrix, r, c: int): float =
+  m.data[r * m.cols + c]
+
+proc `[]=`(m: var Matrix, r, c: int, v: float) =
+  m.data[r * m.cols + c] = v
+
+var m = newMatrix(2, 2)
+m[0, 0] = 1.0
+m[1, 1] = 2.0
+echo m[0, 0]
+echo m[1, 1]