fix #24153, make <| right associative (#24243)

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]).
 

base/show.jl

@@ -654,7 +654,8 @@ julia> Base.operator_associativity(:⊗), Base.operator_associativity(:sin), Bas
 ```
 """
 function operator_associativity(s::Symbol)
-    if operator_precedence(s) in (prec_arrow, prec_assignment, prec_control_flow, prec_power) || isunaryoperator(s) && !is_unary_and_binary_operator(s)
+    if operator_precedence(s) in (prec_arrow, prec_assignment, prec_control_flow, prec_power) ||
+        (isunaryoperator(s) && !is_unary_and_binary_operator(s)) || s === :<|
         return :right
     elseif operator_precedence(s) in (0, prec_comparison) || s in (:+, :++, :*)
         return :none

doc/src/manual/mathematical-operations.md

@@ -360,7 +360,9 @@ 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                       |
+| Syntax         | `<\|`                                                                                             | Right                      |
 | Comparisons    | `> < >= <= == === != !== <:`                                                                      | Non-associative            |
 | Control flow   | `&&` followed by `\|\|` followed by `?`                                                           | Right                      |
 | Assignments    | `= += -= *= /= //= \= ^= ÷= %= \|= &= ⊻= <<= >>= >>>=`                                            | Right                      |

src/julia-parser.scm

@@ -18,7 +18,8 @@
 (define prec-comparison
   (append! '(|<:| |>:| in isa)
            (add-dots '(> < >= ≥ <= ≤ == === ≡ != ≠ !== ≢ ∈ ∉ ∋ ∌ ⊆ ⊈ ⊂ ⊄ ⊊ ∝ ∊ ∍ ∥ ∦ ∷ ∺ ∻ ∽ ∾ ≁ ≃ ≄ ≅ ≆ ≇ ≈ ≉ ≊ ≋ ≌ ≍ ≎ ≐ ≑ ≒ ≓ ≔ ≕ ≖ ≗ ≘ ≙ ≚ ≛ ≜ ≝ ≞ ≟ ≣ ≦ ≧ ≨ ≩ ≪ ≫ ≬ ≭ ≮ ≯ ≰ ≱ ≲ ≳ ≴ ≵ ≶ ≷ ≸ ≹ ≺ ≻ ≼ ≽ ≾ ≿ ⊀ ⊁ ⊃ ⊅ ⊇ ⊉ ⊋ ⊏ ⊐ ⊑ ⊒ ⊜ ⊩ ⊬ ⊮ ⊰ ⊱ ⊲ ⊳ ⊴ ⊵ ⊶ ⊷ ⋍ ⋐ ⋑ ⋕ ⋖ ⋗ ⋘ ⋙ ⋚ ⋛ ⋜ ⋝ ⋞ ⋟ ⋠ ⋡ ⋢ ⋣ ⋤ ⋥ ⋦ ⋧ ⋨ ⋩ ⋪ ⋫ ⋬ ⋭ ⋲ ⋳ ⋴ ⋵ ⋶ ⋷ ⋸ ⋹ ⋺ ⋻ ⋼ ⋽ ⋾ ⋿ ⟈ ⟉ ⟒ ⦷ ⧀ ⧁ ⧡ ⧣ ⧤ ⧥ ⩦ ⩧ ⩪ ⩫ ⩬ ⩭ ⩮ ⩯ ⩰ ⩱ ⩲ ⩳ ⩴ ⩵ ⩶ ⩷ ⩸ ⩹ ⩺ ⩻ ⩼ ⩽ ⩾ ⩿ ⪀ ⪁ ⪂ ⪃ ⪄ ⪅ ⪆ ⪇ ⪈ ⪉ ⪊ ⪋ ⪌ ⪍ ⪎ ⪏ ⪐ ⪑ ⪒ ⪓ ⪔ ⪕ ⪖ ⪗ ⪘ ⪙ ⪚ ⪛ ⪜ ⪝ ⪞ ⪟ ⪠ ⪡ ⪢ ⪣ ⪤ ⪥ ⪦ ⪧ ⪨ ⪩ ⪪ ⪫ ⪬ ⪭ ⪮ ⪯ ⪰ ⪱ ⪲ ⪳ ⪴ ⪵ ⪶ ⪷ ⪸ ⪹ ⪺ ⪻ ⪼ ⪽ ⪾ ⪿ ⫀ ⫁ ⫂ ⫃ ⫄ ⫅ ⫆ ⫇ ⫈ ⫉ ⫊ ⫋ ⫌ ⫍ ⫎ ⫏ ⫐ ⫑ ⫒ ⫓ ⫔ ⫕ ⫖ ⫗ ⫘ ⫙ ⫷ ⫸ ⫹ ⫺ ⊢ ⊣))))
-(define prec-pipe        (add-dots '(|\|>| |<\||)))
+(define prec-pipe<       '(|.<\|| |<\||))
+(define prec-pipe>       '(|.\|>| |\|>|))
 (define prec-colon       '(: |..|))
 (define prec-plus        (append! '($)
                           (add-dots '(+ - |\|| ⊕ ⊖ ⊞ ⊟ |++| ∪ ∨ ⊔ ± ∓ ∔ ∸ ≂ ≏ ⊎ ⊻ ⊽ ⋎ ⋓ ⧺ ⧻ ⨈ ⨢ ⨣ ⨤ ⨥ ⨦ ⨧ ⨨ ⨩ ⨪ ⨫ ⨬ ⨭ ⨮ ⨹ ⨺ ⩁ ⩂ ⩅ ⩊ ⩌ ⩏ ⩐ ⩒ ⩔ ⩖ ⩗ ⩛ ⩝ ⩡ ⩢ ⩣))))
@@ -34,7 +35,7 @@
 
 (define prec-names '(prec-assignment
                      prec-conditional prec-lazy-or prec-lazy-and prec-arrow prec-comparison
-                     prec-pipe prec-colon prec-plus prec-bitshift prec-times prec-rational
+                     prec-pipe< prec-pipe> prec-colon prec-plus prec-bitshift prec-times prec-rational
                      prec-power prec-decl prec-dot))
 
 (define trans-op (string->symbol ".'"))
@@ -802,14 +803,14 @@
 (define (parse-and s)   (parse-RtoL s parse-comparison is-prec-lazy-and? #t parse-and))
 
 (define (parse-comparison s)
-  (let loop ((ex (parse-pipes s))
+  (let loop ((ex (parse-pipe< s))
              (first #t))
     (let ((t (peek-token s)))
       (cond ((is-prec-comparison? t)
              (begin (take-token s)
                     (if first
-                        (loop (list 'comparison ex t (parse-pipes s)) #f)
-                        (loop (append ex (list t (parse-pipes s))) #f))))
+                        (loop (list 'comparison ex t (parse-pipe< s)) #f)
+                        (loop (append ex (list t (parse-pipe< s))) #f))))
             (first ex)
             ((length= ex 4)
              ;; only a single comparison; special chained syntax not required
@@ -821,7 +822,8 @@
                    `(call ,op ,arg1 ,arg2))))
             (else ex)))))
 
-(define (parse-pipes s) (parse-LtoR s parse-range is-prec-pipe?))
+(define (parse-pipe< s) (parse-RtoL s parse-pipe> is-prec-pipe<? #f parse-pipe<))
+(define (parse-pipe> s) (parse-LtoR s parse-range is-prec-pipe>?))
 
 ; parse ranges and postfix ...
 ; colon is strange; 3 arguments with 2 colons yields one call:
@@ -1664,11 +1666,11 @@
                                     #f)
                              #t)))
                      #f))
-         (lhs (parse-pipes s))
+         (lhs (parse-pipe< s))
          (t   (peek-token s)))
     (cond ((memq t '(= in ∈))
            (take-token s)
-           (let* ((rhs (parse-pipes s))
+           (let* ((rhs (parse-pipe< s))
                   (t   (peek-token s)))
              #;(if (not (or (closing-token? t) (newline? t)))
                  ;; should be: (error "invalid iteration specification")

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