destructors: don't produce stupid code for 'cast' (#14208) [backport:1.2]

* destructors: don't produce stupid code for 'cast'

* fixes #14207

compiler/dfa.nim

@@ -541,8 +541,8 @@ template genNoReturn(c: var Con; n: PNode) =
   c.code.add Instr(n: n, kind: goto, dest: high(int) - c.code.len)
 
 proc genRaise(c: var Con; n: PNode) =
-  genJoins(c, n)
   gen(c, n[0])
+  genJoins(c, n)
   if c.inTryStmt > 0:
     c.tryStmtFixups.add c.gotoI(n)
   else:
@@ -553,11 +553,11 @@ proc genImplicitReturn(c: var Con) =
     gen(c, c.owner.ast[resultPos])
 
 proc genReturn(c: var Con; n: PNode) =
-  genJoins(c, n)
   if n[0].kind != nkEmpty:
     gen(c, n[0])
   else:
     genImplicitReturn(c)
+  genJoins(c, n)
   genNoReturn(c, n)
 
 const

compiler/injectdestructors.nim

@@ -957,6 +957,10 @@ proc p(n: PNode; c: var Con; mode: ProcessMode): PNode =
       for i in 0..<n.len:
         result[i] = p(n[i], c, mode)
       inc c.hasUnstructuredCf
+    of nkCast:
+      result = shallowCopy(n)
+      result[0] = n[0]
+      result[1] = p(n[1], c, mode)
     else:
       result = shallowCopy(n)
       for i in 0..<n.len:

tests/arc/tarcmisc.nim

@@ -1,5 +1,6 @@
 discard """
   output: '''
+123xyzabc
 destroyed: false
 destroyed: false
 closed
@@ -8,6 +9,19 @@ destroying variable
   cmd: "nim c --gc:arc $file"
 """
 
+proc takeSink(x: sink string): bool = true
+
+proc b(x: sink string): string =
+  if takeSink(x):
+    return x & "abc"
+
+proc bbb(inp: string) =
+  let y = inp & "xyz"
+  echo b(y)
+
+bbb("123")
+
+
 # bug #13691
 type Variable = ref object
   value: int