enforce 'var T' produces a view into the first parameter; refs #7373

tests/varres/twrong_parameter.nim

@@ -0,0 +1,12 @@
+discard """
+  line: 6
+  errormsg: "'x' is not the first parameter; context: 'x'"
+"""
+
+proc forward(abc: int; x: var int): var int = result = x
+
+proc foo(): var int =
+  var y = 9
+  result = forward(45, y)
+
+echo foo()