noRewrite pragma doesn't prevent rewrites

[exelotl]

While playing with term rewriting macros, I found that the {.noRewrite.} pragma doesn't behave as expected at all.

Example

# test 1
# ------

proc get(x: int): int = x

template t{get(a)}(a: int): int =
  {.noRewrite.}:
    get(a) + 1

echo get(0)


# test 2
# ------

var x: int

template asgn{a = b}(a: int{lvalue}, b: int) =
  {.noRewrite.}:
    a = b + 1

x = 10
echo x

Current output

Tested from Nim 0.20.0 to 1.4.2:

49
85

Expected output

1
11

Additional information

The output on Nim 0.19.6 is different, test 2 gives the correct result:

98
11

[exelotl]

Workaround:
Depending on the use case, you may be able to use a helper proc defined before the term-rewriting macro, to which the rules of the macro don't apply:

# test 1
# ------

proc get(x: int): int = x

proc getFinal(x: int): int {.inline.} =
  get(x)

template t{get(a)}(a: int): int =
    getFinal(a) + 1

echo get(0)


# test 2
# ------

var x: int

proc asgnFinal[T](a: var T, b: T) {.inline.} =
  a = b

template asgn{a = b}(a: int{lvalue}, b: int) =
  asgnFinal(a, b + 1)

x = 10
echo x

Output:

1
11