Handle (Instance Foo) where Foo is unbound.

Return correct error behavior.

svn: r12410

original commit: 541a47f7fd943f77f82983bd52a837db47b736a8

collects/drscheme/private/prefs-contract.ss

@@ -1,16 +0,0 @@
-#lang scheme/base
-
-(require (for-syntax scheme/base)
-         framework/framework)
-
-(provide (rename-out [-preferences:get preferences:get])
-         preferences:get-drscheme:large-letters-font)
-
-(define (preferences:get-drscheme:large-letters-font)
-  (preferences:get 'drscheme:large-letters-font))
-
-(define-syntax (-preferences:get stx)
-  (syntax-case stx (quote)
-    [(_ (quote sym))
-     (with-syntax ([nm (datum->syntax stx (string->symbol (string-append "preferences:get" "-" (symbol->string (syntax-e #'sym)))))])
-       (syntax/loc stx (nm)))]))

collects/typed-scheme/private/parse-type.ss

@@ -47,7 +47,7 @@
       [(Instance t)
        (eq? (syntax-e #'Instance) 'Instance)
        (let ([v (parse-type #'t)])
-         (if (not (or (Mu? v) (Class? v) (Union? v)))
+         (if (not (or (Mu? v) (Class? v) (Union? v) (Error? v)))
              (begin (tc-error/delayed "Argument to Instance must be a class type, got ~a" v)
                     (make-Instance (Un)))
              (make-Instance v)))]

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

@@ -325,7 +325,7 @@
               (begin (check-below ret-ty expected) (ret expected))
               ret-ty))]
        [(tc-result: t) (int-err "non-symbol methods not supported by Typed Scheme: ~a" t)])]
-    [(tc-result: t) (tc-error/expr #:return (or expected (Un)) "send: expected a class instance, got ~a" t)]))
+    [(tc-result: t) (tc-error/expr #:return (or expected (ret (Un))) "send: expected a class instance, got ~a" t)]))
 
 ;; type-check a list of exprs, producing the type of the last one.
 ;; if the list is empty, the type is Void.