cs: fix hash{,eq,eqv} on an odd number of arguments

Closes #3051

pkgs/racket-test-core/tests/racket/basic.rktl

@@ -394,6 +394,16 @@
 (test #t eq? (hasheq) (hash-remove (hasheq 3 4) 3))
 (test #t eq? (hasheqv) (hash-remove (hasheqv 3 4) 3))
 
+(err/rt-test (hash 1))
+(err/rt-test (hasheqv 1))
+(err/rt-test (hasheq 1))
+(err/rt-test (make-hash 1))
+(err/rt-test (make-hasheqv 1))
+(err/rt-test (make-hasheq 1))
+(err/rt-test (make-weak-hash 1))
+(err/rt-test (make-weak-hasheqv 1))
+(err/rt-test (make-weak-hasheq 1))
+
 (test #t symbol? 'foo)
 (test #t symbol? (car '(a b)))
 (test #f symbol? "bar")

racket/src/cs/rumble/hash.ss

@@ -73,6 +73,11 @@
            (let loop ([kvs kvs] [h empty-hash])
              (cond
               [(null? kvs) h]
+              [(null? (cdr kvs))
+               (raise-arguments-error
+                'vararg-ctor
+                "key does not have a value (i.e., an odd number of arguments were provided)"
+                "key" (car kvs))]
               [else (loop (cddr kvs) (intmap-set h (car kvs) (cadr kvs)))]))]))
 
        (define list-ctor