TR: `for` forms generalize types of sequences

Originally submitted on: Sat Dec 27 22:44:01 -0500 2014

The error in reproduction steps is

Type Checker: type mismatch
expected: Nonnegative-Real
given: Real in: r

Either of these works around it:

(for ([r : Nonnegative-Real  (ann '(1 2 3 4) (Sequenceof Nonnegative-Real))])
  (ann r Nonnegative-Real))

(for ([r  (in-list (ann '(1 2 3 4) (Listof Nonnegative-Real)))])
  (ann r Nonnegative-Real))

Steps to Reproduce:

#lang typed/racket

(for ([r  (ann '(1 2 3 4) (Sequenceof Nonnegative-Real))])
  (ann r Nonnegative-Real))

Release:

6.1.1.6--2014-12-21(-/f)

Environment:

unix "Linux snoopy 3.13.0-37-generic #64-Ubuntu SMP Mon Sep 22 21:28:38 UTC 2014 x86_64
 x86_64 x86_64 GNU/Linux" (x86_64-linux/3m) (get-display-depth) = 32
Human Language: english
(current-memory-use) 1319035472
raco pkg (show):
Installation-wide:
 Package                 Checksum           Source
 disassemble             cf0ee3a5...        catalog...ssemble
 drbayes                                    link...il/drbayes
 main-distribution       67868e03...        catalog...ibution
 main-distribution-test  ca4a870e...        catalog...on-test
 nonplussed              f6c06999...        url.../nonplussed
 optimization-coach      be5f7908...        catalog...n-coach
 pict3d                                     link...eil/pict3d
 plot                    e536986e...        clone...path=plot
 racket-lib                                 static-link...lib
 rsound                  4f5d4d15...        catalog rsound
 slideshow-latex         9275fecb...        catalog...w-latex
 [214 auto-installed packages not shown]
User-specific for installation "development":
 [none]



Collections:
("/home/neil/.racket/development/collects"
 (non-existent-path))
("/home/neil/plt-fresh/racket/collects"
 (".gitignore" "acks" "compiler" "data" "db" "dynext" "ffi" "file" "info" "info-domain"
 "json" "launcher" "net" "openssl" "pkg" "planet" "racket" "raco" "reader" "realm" "s-exp"
 "setup" "syntax" "unstable" "version" "xml"))

Recent Internal Errors: Saved 1 internal error:

sequence-contract-violation: negative: method set-max-width cannot be called, except in
 states (unlocked write-lock), args 1221
  context...:
   /home/neil/plt-fresh/racket/collects/racket/private/more-scheme.rkt:147:2:
 call-with-break-parameterization
   /home/neil/plt-fresh/racket/collects/racket/private/more-scheme.rkt:264:2:
 call-with-exception-handler

Computer Language: (("Determine language from source") (#(#t print mixed-fraction-e #f #t
 none) (default) #() "#lang racket\n" #t #f ((test) (main)) #t))

This bug was converted from Gnats bug 14903.