fixes #26019; deepCopy should not be allowed for non-copyable type (#26030)

fixes #26019

compiler/ccgexprs.nim

@@ -3143,6 +3143,12 @@ proc genMagicExpr(p: BProc, e: PNode, d: var TLoc, op: TMagic) =
       localError(p.config, e.info,
         "for --mm:arc|atomicArc|orc 'deepcopy' support has to be enabled with --deepcopy:on")
 
+    let typ = e[1].typ.skipTypes({tyVar, tyRef, tyGenericInst, tyTypeDesc,
+                                   tyAlias, tyInferred, tySink, tyLent, tyOwned})
+    if hasDisabledAsgn(p.module.g.graph, typ):
+      localError(p.config, e.info,
+        "'deepCopy' is not available for type <" & typeToString(typ) & ">")
+
     let x = if e[1].kind in {nkAddr, nkHiddenAddr}: e[1][0] else: e[1]
     var a = initLocExpr(p, x)
     var b = initLocExpr(p, e[2])

tests/system/tdeepcopy_nocopy.nim

@@ -0,0 +1,12 @@
+discard """
+  matrix: "--mm:refc; --mm:orc --deepcopy:on"
+  errormsg: "'deepCopy' is not available for type <NoCopy>"
+  file: "system.nim"
+"""
+
+type NoCopy = object
+
+proc `=copy`(a: var NoCopy; b: NoCopy) {.error.}
+
+var a = new NoCopy
+var b = deepCopy(a)

tests/system/tdeepcopy_nocopy_field.nim

@@ -0,0 +1,15 @@
+discard """
+  matrix: "--mm:refc; --mm:orc --deepcopy:on"
+  errormsg: "'deepCopy' is not available for type <Container>"
+  file: "system.nim"
+"""
+
+type
+  NoCopy = object
+  Container = object
+    value: NoCopy
+
+proc `=copy`(a: var NoCopy; b: NoCopy) {.error.}
+
+var a = new Container
+var b = deepCopy(a)