streamline a[begin] lowering via firstindex(a, n) (JuliaLang#35779)

NEWS.md

@@ -44,6 +44,7 @@ Language changes
  a function like other operators. The dotted version `.-->` is now parsed as well.
  For backwards compatibility, `-->` still parses using its own expression head
  instead of `:call`.
+* The `a[begin]` syntax now calls `firstindex(a,1)` rather than `first(axes(a,1))` ([#35779]).
 * `⌿` (U+233F) and `¦` (U+00A6) are now infix operators with times-like and plus-like precedence,
  respectively. Previously they were parsed as identifier characters ([#37973]).
 

src/julia-syntax.scm

@@ -105,7 +105,7 @@
  (if (null? tuples)
  (if (and last (= n 1))
  `(call (top firstindex) ,a)
- `(call (top first) (call (top axes) ,a ,n)))
+ `(call (top firstindex) ,a ,n))
  (let ((dimno `(call (top +) ,(- n (length tuples))
  ,.(map (lambda (t) `(call (top length) ,t))
  tuples))))