fixes #19291; implements wasMoved hook (#21303)

* fixes #19291; implements `wasMoved` hook

* basics

* checkpoint

* finish `wasMoved`

* add a test for #19291

* add documentation and changelog

* work `attachedWasMoved` with generics

* fixes optimizer

* register `=wasMoved`

* handle wasMoved magcis

* check another round

* some patches

* try `op == nil`

* nicer

* generate `wasMoved` before `destroy`

* try again

* fixes tests

* default wasMoved

* Update tests/destructor/tv2_cast.nim

* Update tests/destructor/tv2_cast.nim

* Update tests/arc/topt_refcursors.nim

tests/arc/topt_no_cursor.nim

@@ -1,7 +1,8 @@
 discard """
   nimoutFull: true
   cmd: '''nim c -r --warnings:off --hints:off --gc:arc --expandArc:newTarget --expandArc:delete --expandArc:p1 --expandArc:tt --hint:Performance:off --assertions:off --expandArc:extractConfig --expandArc:mergeShadowScope --expandArc:check $file'''
-  nimout: '''--expandArc: newTarget
+  nimout: '''
+--expandArc: newTarget
 
 var
   splat
@@ -11,9 +12,9 @@ splat = splitDrive do:
   let blitTmp = path
   blitTmp
 :tmp = splat.drive
-wasMoved(splat.drive)
+`=wasMoved`(splat.drive)
 :tmp_1 = splat.path_1
-wasMoved(splat.path_1)
+`=wasMoved`(splat.path_1)
 result = (
   let blitTmp_1 = :tmp
   blitTmp_1,
@@ -60,10 +61,10 @@ var
 try:
   it_cursor = x
   a = (
-    wasMoved(:tmpD)
+    `=wasMoved`(:tmpD)
     `=copy`(:tmpD, it_cursor.key)
     :tmpD,
-    wasMoved(:tmpD_1)
+    `=wasMoved`(:tmpD_1)
     `=copy`(:tmpD_1, it_cursor.val)
     :tmpD_1)
   echo [
@@ -112,7 +113,7 @@ block :tmp:
       var :tmpD
       sym = shadowScope.symbols[i]
       addInterfaceDecl(c):
-        wasMoved(:tmpD)
+        `=wasMoved`(:tmpD)
         `=copy_1`(:tmpD, sym)
         :tmpD
       inc(i, 1)
@@ -125,7 +126,7 @@ this.isValid = fileExists(this.value)
 if dirExists(this.value):
   var :tmpD
   par = (dir:
-    wasMoved(:tmpD)
+    `=wasMoved`(:tmpD)
     `=copy`(:tmpD, this.value)
     :tmpD, front: "") else:
   var
@@ -133,10 +134,10 @@ if dirExists(this.value):
     :tmpD_2
     :tmpD_3
   par = (dir_1: parentDir(this.value), front_1:
-    wasMoved(:tmpD_1)
+    `=wasMoved`(:tmpD_1)
     `=copy`(:tmpD_1,
       :tmpD_3 = splitDrive do:
-        wasMoved(:tmpD_2)
+        `=wasMoved`(:tmpD_2)
         `=copy`(:tmpD_2, this.value)
         :tmpD_2
       :tmpD_3.path)

tests/arc/topt_refcursors.nim

@@ -1,7 +1,8 @@
 discard """
   output: ''''''
   cmd: '''nim c --gc:arc --expandArc:traverse --hint:Performance:off $file'''
-  nimout: '''--expandArc: traverse
+  nimout: '''
+--expandArc: traverse
 
 var
   it_cursor
@@ -22,12 +23,13 @@ try:
         `=copy`(ri_1, jt.ri)
         echo [jt.s]
         `=sink`(jt, ri_1)
-        wasMoved(ri_1)
+        `=wasMoved`(ri_1)
       finally:
         `=destroy`(ri_1)
 finally:
   `=destroy`(jt)
--- end of expandArc ------------------------'''
+-- end of expandArc ------------------------
+'''
 """
 
 type

tests/arc/topt_wasmoved_destroy_pairs.nim

@@ -1,7 +1,8 @@
 discard """
   output: ''''''
   cmd: '''nim c --gc:arc --expandArc:main --expandArc:tfor --hint:Performance:off $file'''
-  nimout: '''--expandArc: main
+  nimout: '''
+--expandArc: main
 
 var
   a
@@ -29,6 +30,7 @@ try:
   x = f()
   block :tmp:
     var i_cursor
+    mixin inc
     var i_1 = 0
     block :tmp_1:
       while i_1 < 4:
@@ -37,25 +39,26 @@ try:
         if i_cursor == 2:
           return
         add(a):
-          wasMoved(:tmpD)
+          `=wasMoved`(:tmpD)
           `=copy`(:tmpD, x)
           :tmpD
         inc i_1, 1
   if cond:
     add(a):
       let blitTmp = x
-      wasMoved(x)
+      `=wasMoved`(x)
       blitTmp
   else:
     add(b):
       let blitTmp_1 = x
-      wasMoved(x)
+      `=wasMoved`(x)
       blitTmp_1
 finally:
   `=destroy`(x)
   `=destroy_1`(b)
   `=destroy_1`(a)
--- end of expandArc ------------------------'''
+-- end of expandArc ------------------------
+'''
 """
 
 proc f(): seq[int] =