fix JuliaLang#37134, error with macro returning x::T -> y (JuliaLan…

…g#37181)

src/macroexpand.scm

@@ -280,6 +280,13 @@
  (cdr e))))
  (else (other e))))
 
+;; given the LHS of e.g. `x::Int -> y`, wrap the signature in `tuple` to normalize
+(define (tuple-wrap-arrow-sig e)
+ (cond ((atom? e) `(tuple ,e))
+ ((eq? (car e) 'where) `(where ,(tuple-wrap-arrow-arglist (cadr e)) ,@(cddr e)))
+ ((eq? (car e) 'tuple) e)
+ (else `(tuple ,e))))
+
 (define (new-expansion-env-for x env (outermost #f))
  (let ((introduced (pattern-expand1 vars-introduced-by-patterns x)))
  (if (or (atom? x)
@@ -370,7 +377,11 @@
  (resolve-expansion-vars- x env m parent-scope #f)))
  (cdr e))))
 
- ((= function ->)
+ ((->)
+ `(-> ,(resolve-in-function-lhs (tuple-wrap-arrow-sig (cadr e)) env m parent-scope inarg)
+ ,(resolve-expansion-vars-with-new-env (caddr e) env m parent-scope inarg)))
+
+ ((= function)
  (if (and (pair? (cadr e)) (function-def? e))
  ;; in (kw x 1) inside an arglist, the x isn't actually a kwarg
  `(,(car e) ,(resolve-in-function-lhs (cadr e) env m parent-scope inarg)

test/syntax.jl

@@ -2287,6 +2287,13 @@ macro m36272()
 end
 @test @m36272()(1) == 1
 
+# issue #37134
+macro m37134()
+ :(x :: Int -> 62)
+end
+@test @m37134()(1) == 62
+@test_throws MethodError @m37134()(1.0) == 62
+
 @testset "unary ± and ∓" begin
  @test Meta.parse("±x") == Expr(:call, :±, :x)
  @test Meta.parse("∓x") == Expr(:call, :∓, :x)