From e05b1d210ef851bad691117bbe8818ae2e7c7907 Mon Sep 17 00:00:00 2001
From: Jeff Bezanson <jeff.bezanson@gmail.com>
Date: Fri, 20 Oct 2017 16:06:56 -0400
Subject: [PATCH] fix #24153, make `<|` right associative

---
 NEWS.md                                   |  2 ++
 doc/src/manual/mathematical-operations.md |  3 ++-
 src/julia-parser.scm                      | 11 ++++++++++-
 test/parse.jl                             |  4 ++++
 4 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/NEWS.md b/NEWS.md
index c374310c8d3b05..f19be669efa985 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -44,6 +44,8 @@ Language changes
   * The parsing of `1<<2*3` as `1<<(2*3)` is deprecated, and will change to
     `(1<<2)*3` in a future version ([#13079]).
 
+  * The parsing of `<|` is now right associative. `|>` remains left associative ([#24153]).
+
   * `{ }` expressions now use `braces` and `bracescat` as expression heads instead
     of `cell1d` and `cell2d`, and parse similarly to `vect` and `vcat` ([#8470]).
 
diff --git a/doc/src/manual/mathematical-operations.md b/doc/src/manual/mathematical-operations.md
index 91a429338182d8..077709fb222c6b 100644
--- a/doc/src/manual/mathematical-operations.md
+++ b/doc/src/manual/mathematical-operations.md
@@ -360,7 +360,8 @@ Julia applies the following order and associativity of operations, from highest
 | Multiplication | `* / % & \`                                                                                       | Left[^2]                    |
 | Bitshifts      | `<< >> >>>`                                                                                       | Left                       |
 | Addition       | `+ - \| ⊻`                                                                                        | Left[^2]                    |
-| Syntax         | `: ..` followed by `\|>`                                                                          | Left                       |
+| Syntax         | `: ..`                                                                                            | Left                       |
+| Syntax         | `\|> <\|`                                                                                         | `\|>` Left, `<\|` Right    |
 | Comparisons    | `> < >= <= == === != !== <:`                                                                      | Non-associative            |
 | Control flow   | `&&` followed by `\|\|` followed by `?`                                                           | Right                      |
 | Assignments    | `= += -= *= /= //= \= ^= ÷= %= \|= &= ⊻= <<= >>= >>>=`                                            | Right                      |
diff --git a/src/julia-parser.scm b/src/julia-parser.scm
index 742b2387c9dedc..8d6d395e6e9b6e 100644
--- a/src/julia-parser.scm
+++ b/src/julia-parser.scm
@@ -821,7 +821,16 @@
                    `(call ,op ,arg1 ,arg2))))
             (else ex)))))
 
-(define (parse-pipes s) (parse-LtoR s parse-range is-prec-pipe?))
+(define (parse-pipes s)
+  (let loop ((ex (parse-range s))
+             (t  (peek-token s)))
+    (cond ((or (eq? t '|\|>|) (eq? t '|.\|>|))  ; |> associates left
+           (begin (take-token s)
+                  (loop (list 'call t ex (parse-range s)) (peek-token s))))
+          ((or (eq? t '|<\||) (eq? t '|.<\||))  ; <| associates right
+           (begin (take-token s)
+                  (list 'call t ex (parse-pipes s))))
+          (else ex))))
 
 ; parse ranges and postfix ...
 ; colon is strange; 3 arguments with 2 colons yields one call:
diff --git a/test/parse.jl b/test/parse.jl
index 997c0343a0c8fc..91cb09af425b71 100644
--- a/test/parse.jl
+++ b/test/parse.jl
@@ -384,6 +384,10 @@ end
 
 @test parse("1 == 2|>3") == Expr(:call, :(==), 1, Expr(:call, :(|>), 2, 3))
 
+# issue #24153
+@test parse("a|>b|>c|>d") == parse("((a|>b)|>c)|>d")
+@test parse("a<|b<|c<|d") == parse("a<|(b<|(c<|d))")
+
 # issue #12501 and pr #12502
 parse("""
       baremodule A