Fix parsing of dotted rest when there is an expected type.

Closes PR 13646.

collects/tests/typed-racket/succeed/pr13646.rkt

@@ -0,0 +1,17 @@
+#lang typed/racket
+
+(struct: (A) Queue ([elem : A]))
+
+(: qmap : 
+   (All (A B ...) 
+        (case->
+          ((A -> A) (Queue A) -> (Queue A))
+          ((A B ... B -> A) (Queue A) (Queue B) ... B -> (Queue A)))))
+(define qmap
+  (pcase-lambda:
+    (A B ...)
+    [([func : (A -> A)] [deq  : (Queue A)])
+     deq]
+    [([func : (A B ... B -> A)]
+      [deq  : (Queue A)] . [deqs : (Queue B) ... B])
+     deq]))

collects/typed-racket/typecheck/tc-lambda-unit.rkt

@@ -101,7 +101,7 @@
       [(dotted? rest)
        =>
        (lambda (b)
-         (let ([dty (get-type rest #:default Univ)])
+         (let ([dty (extend-tvars (list b) (get-type rest #:default Univ))])
            (with-lexical-env/extend
             (list rest) (list (make-ListDots dty b))
             (check-body))))]