allow splatting in hvcat syntax (JuliaLang#39249)

base/abstractarray.jl

@@ -1793,6 +1793,10 @@ typed_hcat(T::Type, A::AbstractArray...) = cat_t(T, A...; dims=Val(2))
 
 # 2d horizontal and vertical concatenation
 
+# these are produced in lowering if splatting occurs inside hvcat
+hvcat_rows(rows::Tuple...) = hvcat(map(length, rows), (rows...)...)
+typed_hvcat_rows(T::Type, rows::Tuple...) = typed_hvcat(T, map(length, rows), (rows...)...)
+
 function hvcat(nbc::Integer, as...)
  # nbc = # of block columns
  n = length(as)

src/julia-syntax.scm

@@ -1950,6 +1950,34 @@
  ,@(map expand-forms (cddr e))))
  (cons (car e) (map expand-forms (cdr e))))))
 
+(define (expand-vcat e
+ (vcat '((top vcat)))
+ (hvcat '((top hvcat)))
+ (hvcat_rows '((top hvcat_rows))))
+ (let ((a (cdr e)))
+ (if (any assignment? a)
+ (error (string "misplaced assignment statement in \"" (deparse e) "\"")))
+ (if (has-parameters? a)
+ (error "unexpected semicolon in array expression")
+ (expand-forms
+ (if (any (lambda (x)
+ (and (pair? x) (eq? (car x) 'row)))
+ a)
+ ;; convert nested hcat inside vcat to hvcat
+ (let ((rows (map (lambda (x)
+ (if (and (pair? x) (eq? (car x) 'row))
+ (cdr x)
+ (list x)))
+ a)))
+ ;; in case there is splatting inside `hvcat`, collect each row as a
+ ;; separate tuple and pass those to `hvcat_rows` instead (ref #38844)
+ (if (any (lambda (row) (any vararg? row)) rows)
+ `(call ,@hvcat_rows ,@(map (lambda (x) `(tuple ,@x)) rows))
+ `(call ,@hvcat
+ (tuple ,@(map length rows))
+ ,@(apply append rows))))
+ `(call ,@vcat ,@a))))))
+
 (define (expand-tuple-destruct lhss x)
  (define (sides-match? l r)
  ;; l and r either have equal lengths, or r has a trailing ...
@@ -2449,27 +2477,7 @@
  (error (string "misplaced assignment statement in \"" (deparse e) "\"")))
  (expand-forms `(call (top hcat) ,@(cdr e))))
 
- 'vcat
- (lambda (e)
- (let ((a (cdr e)))
- (if (any assignment? a)
- (error (string "misplaced assignment statement in \"" (deparse e) "\"")))
- (if (has-parameters? a)
- (error "unexpected semicolon in array expression")
- (expand-forms
- (if (any (lambda (x)
- (and (pair? x) (eq? (car x) 'row)))
- a)
- ;; convert nested hcat inside vcat to hvcat
- (let ((rows (map (lambda (x)
- (if (and (pair? x) (eq? (car x) 'row))
- (cdr x)
- (list x)))
- a)))
- `(call (top hvcat)
- (tuple ,.(map length rows))
- ,.(apply append rows)))
- `(call (top vcat) ,@a))))))
+ 'vcat expand-vcat
 
  'typed_hcat
  (lambda (e)
@@ -2480,23 +2488,8 @@
  'typed_vcat
  (lambda (e)
  (let ((t (cadr e))
- (a (cddr e)))
- (if (any assignment? (cddr e))
- (error (string "misplaced assignment statement in \"" (deparse e) "\"")))
- (expand-forms
- (if (any (lambda (x)
- (and (pair? x) (eq? (car x) 'row)))
- a)
- ;; convert nested hcat inside vcat to hvcat
- (let ((rows (map (lambda (x)
- (if (and (pair? x) (eq? (car x) 'row))
- (cdr x)
- (list x)))
- a)))
- `(call (top typed_hvcat) ,t
- (tuple ,.(map length rows))
- ,.(apply append rows)))
- `(call (top typed_vcat) ,t ,@a)))))
+ (e (cdr e)))
+ (expand-vcat e `((top typed_vcat) ,t) `((top typed_hvcat) ,t) `((top typed_hvcat_rows) ,t))))
 
  '|'| (lambda (e) (expand-forms `(call |'| ,(cadr e))))
 

test/abstractarray.jl

@@ -1269,3 +1269,14 @@ Base.pushfirst!(tpa::TestPushArray{T}, a::T) where T = pushfirst!(tpa.data, a)
  pushfirst!(tpa, 6, 5, 4, 3, 2)
  @test tpa.data == reverse(collect(1:6))
 end
+
+@testset "splatting into hvcat" begin
+ t = (1, 2)
+ @test [t...; 3 4] == [1 2; 3 4]
+ @test [0 t...; t... 0] == [0 1 2; 1 2 0]
+ @test_throws ArgumentError [t...; 3 4 5]
+
+ @test Int[t...; 3 4] == [1 2; 3 4]
+ @test Int[0 t...; t... 0] == [0 1 2; 1 2 0]
+ @test_throws ArgumentError Int[t...; 3 4 5]
+end