clean up extraneous move sink copy

compiler/ccgexprs.nim

@@ -357,7 +357,7 @@ proc genAssignment(p: BProc, dest, src: TLoc, flags: TAssignmentFlags) =
   of tyString:
     if optSeqDestructors in p.config.globalOptions:
       genGenericAsgn(p, dest, src, flags)
-    elif ({needToCopy, needToCopySinkParam} * flags == {} and src.storage != OnStatic) or canMove(p, src.lode, dest):
+    elif (needToCopy notin flags and src.storage != OnStatic) or canMove(p, src.lode, dest):
       genRefAssign(p, dest, src)
     else:
       if (dest.storage == OnStack and p.config.selectedGC != gcGo) or not usesWriteBarrier(p.config):
@@ -2757,13 +2757,7 @@ proc genMove(p: BProc; n: PNode; d: var TLoc) =
           let val = if p.module.compileToCpp: rdLoc(a) else: byRefLoc(p, a)
           p.s(cpsStmts).addCallStmt(rdLoc(b), val)
     else:
-      if n[1].kind == nkSym and isSinkParam(n[1].sym):
-        var tmp = getTemp(p, n[1].typ.skipTypes({tySink}))
-        genAssignment(p, tmp, a, {needToCopySinkParam})
-        genAssignment(p, d, tmp, {})
-        resetLoc(p, tmp)
-      else:
-        genAssignment(p, d, a, {})
+      genAssignment(p, d, a, {})
       resetLoc(p, a)
 
 proc genDestroy(p: BProc; n: PNode) =

compiler/cgen.nim

@@ -430,7 +430,6 @@ proc rdCharLoc(a: TLoc): Rope =
 type
   TAssignmentFlag = enum
     needToCopy
-    needToCopySinkParam
     needTempForOpenArray
     needAssignCall
   TAssignmentFlags = set[TAssignmentFlag]