Fix internal error when single value expected.

original commit: 979561354d3c0949208e1dd7fed9fe750f4c1cef

collects/tests/typed-scheme/unit-tests/typecheck-tests.rkt

@@ -833,6 +833,7 @@
          (make-pred-ty (-val eof))]
         [tc-e ((inst map Number (Pairof Number Number)) car (ann (list (cons 1 2) (cons 2 3) (cons 4 5)) (Listof (Pairof Number Number))))
               (-lst -Number)]
+        [tc-err (list (values 1 2))]
         )
   (test-suite
    "check-type tests"

collects/typed-scheme/typecheck/tc-expr-unit.rkt

@@ -159,7 +159,7 @@
 
 ;; typecheck an expression, but throw away the effect
 ;; tc-expr/t : Expr -> Type
-(define (tc-expr/t e) (match (tc-expr e)
+(define (tc-expr/t e) (match (single-value e)
                         [(tc-result1: t _ _) t]
                         [t (int-err "tc-expr returned ~a, not a single tc-result, for ~a" t (syntax->datum e))]))