From d23e05f2c314074c0757dbfa88a55c495c5f6d05 Mon Sep 17 00:00:00 2001
From: Asumu Takikawa <asumu@ccs.neu.edu>
Date: Wed, 2 Mar 2016 04:18:06 -0500
Subject: [PATCH] Escape "~" in tc-error/fields arguments

Fixes issue #314
---
 typed-racket-lib/typed-racket/utils/tc-utils.rkt  | 14 ++++++++++----
 typed-racket-test/unit-tests/parse-type-tests.rkt |  3 +++
 2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/typed-racket-lib/typed-racket/utils/tc-utils.rkt b/typed-racket-lib/typed-racket/utils/tc-utils.rkt
index 4d6bb0b6..9a91c70d 100644
--- a/typed-racket-lib/typed-racket/utils/tc-utils.rkt
+++ b/typed-racket-lib/typed-racket/utils/tc-utils.rkt
@@ -202,12 +202,14 @@ don't depend on any other portion of the system
 
 ;; Produce a type error using modern Racket error syntax.
 ;; Avoid using format directives in the `msg`, `more`, and `field`
-;; strings in the rest argument (may cause unexpected errors)
-(define (tc-error/fields msg
-                         #:more [more #f]
+;; strings in the rest argument because they will be escaped.
+(define (tc-error/fields *msg
+                         #:more [*more #f]
                          #:stx [stx (current-orig-stx)]
                          #:delayed? [delayed? #f]
                          . rst)
+  (define msg (escape-~ *msg))
+  (define more (and *more (escape-~ *more)))
   (unless (even? (length rst))
     (raise-argument-error
      'tc-error/fields
@@ -216,7 +218,7 @@ don't depend on any other portion of the system
   (define-values (field-strs vals)
     (for/fold ([field-strs null] [vals null])
               ([field+value (in-slice 2 rst)])
-      (define field (car field+value))
+      (define field (escape-~ (car field+value)))
       (define value (cadr field+value))
       (define field-strs*
         (cons (format "  ~a: ~~a" field) field-strs))
@@ -229,6 +231,10 @@ don't depend on any other portion of the system
       (apply tc-error/delayed #:stx stx final-msg (reverse vals))
       (apply tc-error/stx stx final-msg (reverse vals))))
 
+;; escape "~" to avoid breaking `format` down the line
+(define (escape-~ str)
+  (regexp-replace #rx"~" str "~~"))
+
 ;; produce a type error, using the current syntax
 (define (tc-error msg . rest)
   (let* ([ostx (current-orig-stx)]
diff --git a/typed-racket-test/unit-tests/parse-type-tests.rkt b/typed-racket-test/unit-tests/parse-type-tests.rkt
index 7c2ec486..a16e6937 100644
--- a/typed-racket-test/unit-tests/parse-type-tests.rkt
+++ b/typed-racket-test/unit-tests/parse-type-tests.rkt
@@ -403,6 +403,9 @@
    [FAIL (Unit (import bad) (export) String)]
    [FAIL (Unit (import) (export bad) String)]
    [(Sequenceof Any Any) (-seq Univ Univ)]
+
+   ;; GH issue #314
+   [FAIL ~> #:msg "unbound"]
    ))
 
 ;; FIXME - add tests for parse-values-type, parse-tc-results