Add a line continuation character '⤸'

Closes #27533

src/julia-parser.scm

@@ -503,6 +503,18 @@
              (skip-multiline-comment port 1))
       (skip-to-eol port)))
 
+(define (maybe-continue-line port)
+  (if (not space-sensitive)
+      (error "Line continuation '⤸' is only allowed for space separated lists like macros arugments and matrix literals"))
+  (read-char port) ; Consume ⤸
+  (let ((c (peek-char port)))
+    (if (eof-object? c)
+        (error "incomplete: Line continuation '⤸' is last character in file")) ; NOTE: changing this may affect code in base/client.jl
+    (if (not (eqv? c #\newline))
+        (error (string "Line continuation '⤸' must be followed by a newline. Got \"⤸"
+                       c "\" instead"))))
+  (read-char port))
+
 (define (skip-ws-and-comments port)
   (skip-ws port #t)
   (if (eqv? (peek-char port) #\#)
@@ -530,6 +542,7 @@
           ((string.find "0123456789" c)   (read-number port #f #f))
 
           ((eqv? c #\#)                   (skip-comment port) (next-token port s))
+          ((eqv? c #\⤸)                   (maybe-continue-line port) (next-token port s))
 
           ;; . is difficult to handle; it could start a number or operator
           ((and (eqv? c #\.)

stdlib/REPL/src/latex_symbols.jl

@@ -107,6 +107,7 @@ const latex_symbols = Dict(
     "\\impliedby" => "⟸",
     "\\to" => "→",
     "\\euler" => "ℯ",
+    "\\linecontinuation" => "⤸",
 
     # Superscripts
     "\\^0" => "⁰",

test/syntax.jl

@@ -1719,6 +1719,13 @@ let g = @foo28900 f28900(kwarg = x->2x)
     @test g(10) == 20
 end
 
+# Line continuation - issue #27533
+@test Meta.parse("[1 ⤸\n 2]") == Expr(:hcat, 1, 2)
+@test Meta.parse("@f ⤸\n a") == Expr(:macrocall, Symbol("@f"), LineNumberNode(1, :none), :a)
+@test Meta.isexpr(Meta.parse("@f ⤸"), :incomplete)
+@test_throws ParseError("Line continuation '⤸' is only allowed for space separated lists like macros arugments and matrix literals") Meta.parse("x ⤸\n = 1")
+@test_throws ParseError("Line continuation '⤸' must be followed by a newline. Got \"⤸ \" instead") Meta.parse("@x ⤸ \n")
+
 # issue #26037
 x26037() = 10
 function test_26037()