Close holes in what values can be thrown.

- Don't allow 3d-syntax in the exprs field of `exn:fail:syntax`
- Don't allow throwing arbitrary higher-order values

pkgs/typed-racket-pkgs/typed-racket-lib/typed-racket/base-env/base-env.rkt

@@ -20,7 +20,7 @@
  "base-structs.rkt"
  racket/file
  (only-in racket/private/pre-base new-apply-proc)
- (only-in (types abbrev) [-Boolean B] [-Symbol Sym])
+ (only-in (types abbrev) [-Boolean B] [-Symbol Sym] -Flat)
  (only-in (types numeric-tower) [-Number N])
  (only-in (rep type-rep)
           make-ClassTop
@@ -1146,8 +1146,8 @@
      ((-> ManyUniv) ((list) Univ . ->* . b) . -> . b)))]
 
 ;; Section 10.2
-[raise (cl->* (Univ . -> . (Un))
-              (Univ Univ . -> . (Un)))]
+[raise (cl->* ((Un -Flat -Exn) . -> . (Un))
+              ((Un -Flat -Exn) Univ . -> . (Un)))]
 [error
  (cl->* (-> Sym (Un))
         (->* (list -String) Univ (Un))

pkgs/typed-racket-pkgs/typed-racket-lib/typed-racket/base-env/base-structs.rkt

@@ -10,7 +10,7 @@
 
 (require (for-template racket/base (prefix-in k: '#%kernel)))
 
-(provide initialize-structs -Date -Srcloc -Date -Arity-At-Least)
+(provide initialize-structs -Date -Srcloc -Date -Arity-At-Least -Exn)
 
 (define-syntax define-hierarchy
   (syntax-rules (define-hierarchy)
@@ -82,7 +82,7 @@
         (define-hierarchy exn:fail:contract:continuation (#:kernel-maker k:exn:fail:contract:continuation) ())
         (define-hierarchy exn:fail:contract:variable (#:kernel-maker k:exn:fail:contract:variable) ()))
 
-      (define-hierarchy exn:fail:syntax (#:kernel-maker k:exn:fail:syntax) ([exprs : (-lst (-Syntax Univ))]))
+      (define-hierarchy exn:fail:syntax (#:kernel-maker k:exn:fail:syntax) ([exprs : (-lst Any-Syntax)]))
 
       (define-hierarchy exn:fail:read (#:kernel-maker k:exn:fail:read)
         ([srclocs : (-lst Univ)]) ;; cce: Univ here should be srcloc

pkgs/typed-racket-pkgs/typed-racket-lib/typed-racket/types/abbrev.rkt

@@ -164,6 +164,10 @@
            (make-Vector sexp)
            (make-Box sexp)
            t)))
+(define/decl -Flat
+  (-mu flat
+       (Un -Null -Number -Boolean -Symbol -String -Keyword -Char
+           (-pair flat flat))))
 (define/decl -Sexp (-Sexpof (Un)))
 (define Syntax-Sexp (-Sexpof Any-Syntax))
 (define Ident (-Syntax -Symbol))

pkgs/typed-racket-pkgs/typed-racket-test/tests/typed-racket/unit-tests/typecheck-tests.rkt

@@ -3176,6 +3176,14 @@
         #:ret (ret -String)
         #:msg #rx"expected: Symbol.*given: Any"]
        
+       [tc-err
+        (raise (λ ([x : Number]) (add1 x)))
+        #:ret (ret (Un))]
+       
+       [tc-err
+        (exn:fail:syntax "" (current-continuation-marks) (list (datum->syntax #f add1)))
+        #:ret (ret -Exn)]
+
        ;; PR 14218
        [tc-e (ann (values "foo" "bar") (Values String String))
              #:ret (ret (list -String -String))]