parse A=>B as a call

NEWS.md

@@ -157,6 +157,9 @@ This section lists changes that do not have deprecation warnings.
       that internally uses twice-precision arithmetic.  These two
       outcomes exhibit differences in both precision and speed.
 
+  * `A=>B` expressions are now parsed as calls instead of using `=>` as the
+    expression head ([#20327]).
+
 Library improvements
 --------------------
 

base/show.jl

@@ -471,7 +471,7 @@ const uni_ops = Set{Symbol}([:(+), :(-), :(!), :(¬), :(~), :(<:), :(>:), :(√)
 const expr_infix_wide = Set{Symbol}([
     :(=), :(+=), :(-=), :(*=), :(/=), :(\=), :(^=), :(&=), :(|=), :(÷=), :(%=), :(>>>=), :(>>=), :(<<=),
     :(.=), :(.+=), :(.-=), :(.*=), :(./=), :(.\=), :(.^=), :(.&=), :(.|=), :(.÷=), :(.%=), :(.>>>=), :(.>>=), :(.<<=),
-    :(&&), :(||), :(<:), :(=>), :($=), :(⊻=)]) # `$=` should be removed after deprecation is removed, issue #18977
+    :(&&), :(||), :(<:), :($=), :(⊻=)]) # `$=` should be removed after deprecation is removed, issue #18977
 const expr_infix = Set{Symbol}([:(:), :(->), Symbol("::")])
 const expr_infix_any = union(expr_infix, expr_infix_wide)
 const all_ops = union(quoted_syms, uni_ops, expr_infix_any)

base/test.jl

@@ -954,7 +954,7 @@ function parse_testset_args(args)
         elseif isa(arg, Expr) && arg.head == :(=)
             # we're building up a Dict literal here
             key = Expr(:quote, arg.args[1])
-            push!(options.args, Expr(:(=>), key, arg.args[2]))
+            push!(options.args, Expr(:call, :(=>), key, arg.args[2]))
         else
             error("Unexpected argument $arg to @testset")
         end

src/julia-parser.scm

@@ -73,7 +73,7 @@
 ; operators that are special forms, not function names
 (define syntactic-operators
   (append! (add-dots '(= += -= *= /= //= |\\=| ^= ÷= %= <<= >>= >>>= |\|=| &= ⊻=))
-           '(:= --> $= => && |\|\|| |.| ... ->)))
+           '(:= --> $= && |\|\|| |.| ... ->)))
 (define syntactic-unary-operators '($ & |::|))
 
 (define syntactic-op? (Set syntactic-operators))
@@ -753,7 +753,9 @@
                        (let ((args (parse-chain s down '~)))
                          `(macrocall @~ ,ex ,@(butlast args)
                                      ,(loop (last args) (peek-token s)))))
-                   (list t ex (parse-assignment s down)))))))
+                   (if (eq? t '=>)  ;; => is the only non-syntactic assignment-precedence operator
+                       (list 'call t ex (parse-assignment s down))
+                       (list       t ex (parse-assignment s down))))))))
 
 (define (parse-eq s)
   (let ((lno (input-port-line (ts:port s))))
@@ -893,11 +895,7 @@
           (else ex))))
 
 (define (invalid-identifier-name? ex)
-  ;; TODO: remove this hack when we remove the special Dict syntax
-  ;; TODO: Dict syntax removed, but need to decide whether to change the parsing
-  ;; of `a=>b` to use `call`.
-  (or (and (not (eq? ex '=>)) (syntactic-op? ex))
-      (eq? ex '....)))
+  (or (syntactic-op? ex) (eq? ex '....)))
 
 (define (parse-unary s)
   (let ((t (require-token s)))

src/julia-syntax.scm

@@ -2049,9 +2049,6 @@
          (error "assignment not allowed inside tuple"))
      (expand-forms `(call (core tuple) ,@(cdr e))))
 
-   '=>
-   (lambda (e) `(call => ,(expand-forms (cadr e)) ,(expand-forms (caddr e))))
-
    'cell1d (lambda (e) (error "{ } vector syntax is discontinued"))
    'cell2d (lambda (e) (error "{ } matrix syntax is discontinued"))