Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

implement property destructuring #39285

Merged
merged 2 commits into from
Jan 23, 2021
+108 −59
Merged

implement property destructuring #39285

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
5f60a84
implement property destructuring
simeonschaub Jan 16, 2021
d2e2a9b
add NEWS entry
simeonschaub Jan 21, 2021
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
3 changes: 3 additions & 0 deletions NEWS.md
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,9 @@ Julia v1.7 Release Notes
New language features
---------------------

* `(; a, b) = x` can now be used to destructure properties `a` and `b` of `x`. This syntax is equivalent to `a = getproperty(x, :a)`
and similarly for `b`. ([#39285])

Language changes
----------------

Expand Down
135 changes: 76 additions & 59 deletions src/julia-syntax.scm
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1950,6 +1950,66 @@
,@(map expand-forms (cddr e))))
(cons (car e) (map expand-forms (cdr e))))))

(define (expand-tuple-destruct lhss x)
(define (sides-match? l r)
;; l and r either have equal lengths, or r has a trailing ...
(cond ((null? l) (null? r))
((vararg? (car l)) #t)
((null? r) #f)
((vararg? (car r)) (null? (cdr r)))
(else (sides-match? (cdr l) (cdr r)))))
(if (and (pair? x) (pair? lhss) (eq? (car x) 'tuple) (not (any assignment? (cdr x)))
(not (has-parameters? (cdr x)))
(sides-match? lhss (cdr x)))
;; (a, b, ...) = (x, y, ...)
(expand-forms
(tuple-to-assignments lhss x))
;; (a, b, ...) = other
(begin
;; like memq, but if last element of lhss is (... sym),
;; check against sym instead
(define (in-lhs? x lhss)
(if (null? lhss)
#f
(let ((l (car lhss)))
(cond ((and (pair? l) (eq? (car l) '|...|))
(if (null? (cdr lhss))
(eq? (cadr l) x)
(error (string "invalid \"...\" on non-final assignment location \""
(cadr l) "\""))))
((eq? l x) #t)
(else (in-lhs? x (cdr lhss)))))))
;; in-lhs? also checks for invalid syntax, so always call it first
(let* ((xx (if (or (and (not (in-lhs? x lhss)) (symbol? x))
(ssavalue? x))
x (make-ssavalue)))
(ini (if (eq? x xx) '() (list (sink-assignment xx (expand-forms x)))))
(n (length lhss))
;; skip last assignment if it is an all-underscore vararg
(n (if (> n 0)
(let ((l (last lhss)))
(if (and (vararg? l) (underscore-symbol? (cadr l)))
(- n 1)
n))
n))
(st (gensy)))
`(block
,@(if (> n 0) `((local ,st)) '())
,@ini
,@(map (lambda (i lhs)
(expand-forms
(if (vararg? lhs)
`(= ,(cadr lhs) (call (top rest) ,xx ,@(if (eq? i 0) '() `(,st))))
(lower-tuple-assignment
(if (= i (- n 1))
(list lhs)
(list lhs st))
`(call (top indexed_iterate)
,xx ,(+ i 1) ,@(if (eq? i 0) '() `(,st)))))))
(iota n)
lhss)
(unnecessary ,xx))))))
Comment on lines +1953 to +2011
Copy link
Member Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

NFC here, the level of indenting was just getting a bit much, so I moved this into a separate function.


;; move an assignment into the last statement of a block to keep more statements at top level
(define (sink-assignment lhs rhs)
(if (and (pair? rhs) (eq? (car rhs) 'block))
Expand Down Expand Up @@ -2102,67 +2162,24 @@
(call (top setproperty!) ,aa ,bb ,rr)
(unnecessary ,rr)))))
((tuple)
;; multiple assignment
(let ((lhss (cdr lhs))
(x (caddr e)))
(define (sides-match? l r)
;; l and r either have equal lengths, or r has a trailing ...
(cond ((null? l) (null? r))
((vararg? (car l)) #t)
((null? r) #f)
((vararg? (car r)) (null? (cdr r)))
(else (sides-match? (cdr l) (cdr r)))))
(if (and (pair? x) (pair? lhss) (eq? (car x) 'tuple) (not (any assignment? (cdr x)))
(not (has-parameters? (cdr x)))
(sides-match? lhss (cdr x)))
;; (a, b, ...) = (x, y, ...)
(expand-forms
(tuple-to-assignments lhss x))
;; (a, b, ...) = other
(begin
;; like memq, but if last element of lhss is (... sym),
;; check against sym instead
(define (in-lhs? x lhss)
(if (null? lhss)
#f
(let ((l (car lhss)))
(cond ((and (pair? l) (eq? (car l) '|...|))
(if (null? (cdr lhss))
(eq? (cadr l) x)
(error (string "invalid \"...\" on non-final assignment location \""
(cadr l) "\""))))
((eq? l x) #t)
(else (in-lhs? x (cdr lhss)))))))
;; in-lhs? also checks for invalid syntax, so always call it first
(let* ((xx (if (or (and (not (in-lhs? x lhss)) (symbol? x))
(ssavalue? x))
x (make-ssavalue)))
(ini (if (eq? x xx) '() (list (sink-assignment xx (expand-forms x)))))
(n (length lhss))
;; skip last assignment if it is an all-underscore vararg
(n (if (> n 0)
(let ((l (last lhss)))
(if (and (vararg? l) (underscore-symbol? (cadr l)))
(- n 1)
n))
n))
(st (gensy)))
`(block
,@(if (> n 0) `((local ,st)) '())
,@ini
,@(map (lambda (i lhs)
(expand-forms
(if (vararg? lhs)
`(= ,(cadr lhs) (call (top rest) ,xx ,@(if (eq? i 0) '() `(,st))))
(lower-tuple-assignment
(if (= i (- n 1))
(list lhs)
(list lhs st))
`(call (top indexed_iterate)
,xx ,(+ i 1) ,@(if (eq? i 0) '() `(,st)))))))
(iota n)
lhss)
(unnecessary ,xx)))))))
(if (has-parameters? lhss)
;; property destructuring
(if (length= lhss 1)
(let* ((xx (if (symbol-like? x) x (make-ssavalue)))
(ini (if (eq? x xx) '() (list (sink-assignment xx (expand-forms x))))))
`(block
,@ini
,@(map (lambda (field)
(if (not (symbol? field))
(error (string "invalid assignment location \"" (deparse lhs) "\"")))
(expand-forms `(= ,field (call (top getproperty) ,xx (quote ,field)))))
(cdar lhss))
(unnecessary ,xx)))
(error (string "invalid assignment location \"" (deparse lhs) "\"")))
;; multiple assignment
(expand-tuple-destruct lhss x))))
((typed_hcat)
(error "invalid spacing in left side of indexed assignment"))
((typed_vcat)
Expand Down
29 changes: 29 additions & 0 deletions test/syntax.jl
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -2649,3 +2649,32 @@ end

# issue #38501
@test :"a $b $("str") c" == Expr(:string, "a ", :b, " ", Expr(:string, "str"), " c")

@testset "property destructuring" begin
res = begin (; num, den) = 1 // 2 end
@test res == 1 // 2
@test num == 1
@test den == 2

res = begin (; b, a) = (a=1, b=2, c=3) end
@test res == (a=1, b=2, c=3)
@test b == 2
@test a == 1

# could make this an error instead, but I think this is reasonable
res = begin (; a, b, a) = (a=5, b=6) end
@test res == (a=5, b=6)
@test a == 5
@test b == 6

@test_throws ErrorException (; a, b) = (x=1,)

@test Meta.isexpr(Meta.@lower(begin (a, b; c) = x end), :error)
@test Meta.isexpr(Meta.@lower(begin (a, b; c) = x, y end), :error)
@test Meta.isexpr(Meta.@lower(begin (; c, a.b) = x end), :error)

f((; a, b)) = a, b
@test f((b=3, a=4)) == (4, 3)
@test f((b=3, c=2, a=4)) == (4, 3)
@test_throws ErrorException f((;))
end