capture macro now accepts variables of different types (nim-lang#13356)

* Capture macro can now accept variables of different types

* Add test

* Update examples

* Use let instead of var

lib/pure/sugar.nim

@@ -165,7 +165,7 @@ template distinctBase*(T: typedesc): typedesc {.deprecated: "use distinctBase fr
   ## reverses ``type T = distinct A``; works recursively.
   typetraits.distinctBase(T)
 
-macro capture*(locals: openArray[typed], body: untyped): untyped {.since: (1, 1).} =
+macro capture*(locals: varargs[typed], body: untyped): untyped {.since: (1, 1).} =
   ## Useful when creating a closure in a loop to capture some local loop variables
   ## by their current iteration values. Example:
   ##
@@ -175,14 +175,16 @@ macro capture*(locals: openArray[typed], body: untyped): untyped {.since: (1, 1)
   ##   for i in 5..7:
   ##     for j in 7..9:
   ##       if i * j == 42:
-  ##         capture [i, j]:
+  ##         capture i, j:
   ##           myClosure = proc () = echo fmt"{i} * {j} = 42"
   ##   myClosure() # output: 6 * 7 == 42
   ##   let m = @[proc (s: string): string = "to " & s, proc (s: string): string = "not to " & s]
-  ##   var l = m.mapIt(capture([it], proc (s: string): string = it(s)))
+  ##   var l = m.mapIt(capture(it, proc (s: string): string = it(s)))
   ##   let r = l.mapIt(it("be"))
   ##   echo r[0] & ", or " & r[1] # output: to be, or not to be
   var params = @[newIdentNode("auto")]
+  let locals = if locals.len == 1 and locals[0].kind == nnkBracket: locals[0]
+               else: locals
   for arg in locals:
     params.add(newIdentDefs(ident(arg.strVal), freshIdentNodes getTypeInst arg))
   result = newNimNode(nnkCall)

tests/closure/tcapture.nim

@@ -2,7 +2,9 @@ discard """
   output: '''
 to be, or not to be
 (v: 1)
+(w: -1)
 (v: 1)
+(w: -1)
 '''
   joinable: false
 """
@@ -14,13 +16,19 @@ var l = m.mapIt(capture([it], proc (s: string): string = it(s)))
 let r = l.mapIt(it("be"))
 echo r[0] & ", or " & r[1]
 
-type O = object
-  v: int
+type
+  O = object
+    v: int
+  U = object
+    w: int
 var o = O(v: 1)
+var u = U(w: -1)
 var execute: proc()
-capture [o]:
+capture o, u:
   execute = proc() =
     echo o
+    echo u
 execute()
 o.v = -1
+u.w = 1
 execute()