add custom pragma support for var and let symbols (#9582)

* add custom pragma support for var and let symbols
* updated changelog for custom pragmas on var and let symbols
* add oldast switch for backwards compatibility

tests/pragmas/tcustom_pragma.nim

@@ -175,24 +175,47 @@ var foo: Something
 foo.cardinal = north
 doAssert foo.b.hasCustomPragma(thingy) == true
 
-
-proc myproc(s: string): int = 
+proc myproc(s: string): int =
   {.thingy.}:
     s.len
 
 doAssert myproc("123") == 3
 
 let xx = compiles:
-  proc myproc_bad(s: string): int = 
+  proc myproc_bad(s: string): int =
     {.not_exist.}:
       s.len
 doAssert: xx == false
 
-
-macro checkSym(s: typed{nkSym}): untyped = 
+macro checkSym(s: typed{nkSym}): untyped =
   let body = s.getImpl.body
   doAssert body[1].kind == nnkPragmaBlock
   doAssert body[1][0].kind == nnkPragma
   doAssert body[1][0][0] == bindSym"thingy"
 
-checkSym(myproc)
+checkSym(myproc)
+
+# var and let pragmas
+block:
+  template myAttr() {.pragma.}
+  template myAttr2(x: int) {.pragma.}
+  template myAttr3(x: string) {.pragma.}
+
+  let a {.myAttr,myAttr2(2),myAttr3:"test".}: int = 0
+  let b {.myAttr,myAttr2(2),myAttr3:"test".} = 0
+  var x {.myAttr,myAttr2(2),myAttr3:"test".}: int = 0
+  var y {.myAttr,myAttr2(2),myAttr3:"test".}: int
+  var z {.myAttr,myAttr2(2),myAttr3:"test".} = 0
+
+  template check(s: untyped) =
+    doAssert s.hasCustomPragma(myAttr)
+    doAssert s.hasCustomPragma(myAttr2)
+    doAssert s.getCustomPragmaVal(myAttr2) == 2
+    doAssert s.hasCustomPragma(myAttr3)
+    doAssert s.getCustomPragmaVal(myAttr3) == "test"
+
+  check(a)
+  check(b)
+  check(x)
+  check(y)
+  check(z)