fix JuliaLang#45024, lost expected assignment after const error (Ju…

…liaLang#45344)

src/julia-parser.scm

@@ -1355,11 +1355,19 @@
  (list 'where (rewrap-where x (cadr w)) (caddr w))
  x))
 
+(define (parse-struct-field s)
+ (let ((tok (peek-token s)))
+ ;; allow `const x` only as a struct field
+ (if (eq? tok 'const)
+ (begin (take-token s)
+ `(const ,(parse-eq s)))
+ (parse-eq s))))
+
 (define (parse-struct-def s mut? word)
  (if (reserved-word? (peek-token s))
  (error (string "invalid type name \"" (take-token s) "\"")))
  (let ((sig (parse-subtype-spec s)))
- (begin0 (list 'struct (if mut? '(true) '(false)) sig (parse-block s))
+ (begin0 (list 'struct (if mut? '(true) '(false)) sig (parse-block s parse-struct-field))
  (expect-end s word))))
 
 ;; consume any number of line endings from a token stream
@@ -1456,7 +1464,13 @@
  `(const ,expr)
  expr)))
  ((const)
- `(const ,(parse-eq s)))
+ (let ((assgn (parse-eq s)))
+ (if (not (and (pair? assgn)
+ (or (eq? (car assgn) '=)
+ (eq? (car assgn) 'global)
+ (eq? (car assgn) 'local))))
+ (error "expected assignment after \"const\"")
+ `(const ,assgn))))
 
  ((function macro)
  (let* ((loc (line-number-node s))

test/syntax.jl

@@ -3369,3 +3369,13 @@ end
 # issue #45162
 f45162(f) = f(x=1)
 @test first(methods(f45162)).called != 0
+
+# issue #45024
+@test_throws ParseError("expected assignment after \"const\"") Meta.parse("const x")
+@test_throws ParseError("expected assignment after \"const\"") Meta.parse("const x::Int")
+# these cases have always been caught during lowering, since (const (global x)) is not
+# ambiguous with the lowered form (const x), but that could probably be changed.
+@test Meta.lower(@__MODULE__, :(global const x)) == Expr(:error, "expected assignment after \"const\"")
+@test Meta.lower(@__MODULE__, :(global const x::Int)) == Expr(:error, "expected assignment after \"const\"")
+@test Meta.lower(@__MODULE__, :(const global x)) == Expr(:error, "expected assignment after \"const\"")
+@test Meta.lower(@__MODULE__, :(const global x::Int)) == Expr(:error, "expected assignment after \"const\"")