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Yet another change to evalOnce #8578

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Yet another change to evalOnce #8578

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42 changes: 17 additions & 25 deletions lib/pure/collections/sequtils.nim
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Original file line number Diff line number Diff line change
Expand Up @@ -635,28 +635,21 @@ template mapIt*(s, typ, op: untyped): untyped =
result.add(op)
result

# This is needed in order not to break the bootstrap, the fallback
# implementation is a "dumb" let that won't work in some cases (eg. when `exp`
# is an openArray)
when declared(macros.symKind):
macro evalOnce(v, exp: untyped): untyped =
expectKind(v, nnkIdent)
var val = exp

result = newStmtList()

# Not a parameter we can pass as-is, evaluate and store in a temporary
# variable
if exp.kind != nnkSym or exp.symKind != nskParam:
val = genSym()
result.add(newLetStmt(val, exp))

result.add(
newProc(name = genSym(nskTemplate, $v), params = [getType(untyped)],
body = val, procType = nnkTemplateDef))
else:
macro evalOnce(v, exp: untyped): untyped =
result = newLetStmt(v, exp)
macro evalOnce(v, exp: untyped): untyped =
expectKind(v, nnkIdent)
var val = exp

result = newStmtList()

# If `exp` is not a symbol we evaluate it once here and then use the temporary
# symbol as alias
if exp.kind != nnkSym:
val = genSym()
result.add(newLetStmt(val, exp))

result.add(
newProc(name = genSym(nskTemplate, $v), params = [getType(untyped)],
body = val, procType = nnkTemplateDef))

template mapIt*(s, op: untyped): untyped =
## Convenience template around the ``map`` proc to reduce typing.
Expand Down Expand Up @@ -1067,9 +1060,8 @@ when isMainModule:
doAssert mapLiterals(([1], ("abc"), 2), `$`, nested=true) == (["1"], "abc", "2")

block: # mapIt with openArray
when declared(macros.symKind):
proc foo(x: openArray[int]): seq[int] = x.mapIt(it + 1)
doAssert foo([1,2,3]) == @[2,3,4]
proc foo(x: openArray[int]): seq[int] = x.mapIt(it + 1)
doAssert foo([1,2,3]) == @[2,3,4]

block: # mapIt with invalid RHS for `let` (#8566)
type X = enum
Expand Down