type mismatch when using Floats with for/sum

[citrusmunch]

What version of Racket are you using?

v8.12 [cs]

What program did you run?

mve

(for/sum : Float ([i : Float (in-range 0 1 0.1)]) i)

What should have happened?

same output as the following program

(for/sum : Real ([i : Real (in-range 0 1 0.1)]) i)

which returns 5.5.

If you got an error message, please include it here.

string:1:0: Type Checker: type mismatch
  expected: Flonum
  given: Zero
  in: (for/sum : Float ((i : Float (in-range 0 1 0.1))) i)
 [,bt for context]

the backtrace, if it's useful :)

string:1:0: Type Checker: type mismatch
  expected: Flonum
  given: Zero
  in: (for/sum : Float ((i : Float (in-range 0 1 0.1))) i)
  location...:
   string:1:0
  context...:
   /Applications/Racket v8.12/share/pkgs/typed-racket-lib/typed-racket/typecheck/check-below.rkt:130:5: perform-check!
   /Applications/Racket v8.12/share/pkgs/typed-racket-lib/typed-racket/private/type-annotation.rkt:83:0: get-type/infer
   /Applications/Racket v8.12/share/pkgs/typed-racket-lib/typed-racket/typecheck/tc-let-unit.rkt:381:0: tc/let-values
   .../private/parse-interp.rkt:643:50
   /Applications/Racket v8.12/share/pkgs/typed-racket-lib/typed-racket/typecheck/tc-expr-unit.rkt:112:0: tc-expr/check
   /Applications/Racket v8.12/share/pkgs/typed-racket-lib/typed-racket/private/type-annotation.rkt:83:0: get-type/infer
   /Applications/Racket v8.12/share/pkgs/typed-racket-lib/typed-racket/typecheck/tc-let-unit.rkt:381:0: tc/let-values
   .../private/parse-interp.rkt:643:50
   /Applications/Racket v8.12/share/pkgs/typed-racket-lib/typed-racket/typecheck/tc-expr-unit.rkt:112:0: tc-expr/check
   [repeats 2 more times]
   .../private/parse-interp.rkt:643:50
   /Applications/Racket v8.12/share/pkgs/typed-racket-lib/typed-racket/typecheck/tc-expr-unit.rkt:112:0: tc-expr/check
   /Applications/Racket v8.12/share/pkgs/typed-racket-lib/typed-racket/typecheck/tc-toplevel.rkt:724:0: tc-toplevel-form
   .../private/parse-interp.rkt:643:50
   /Applications/Racket v8.12/share/pkgs/xrepl-lib/xrepl/xrepl.rkt:1573:0
   /Applications/Racket v8.12/collects/racket/repl.rkt:11:26

from what I can tell, the literal zero in the definition seems to be the issue. The comment a little before seems to acknowledge this as intentional.

typed-racket/typed-racket-lib/typed-racket/base-env/prims.rkt

Lines 523 to 528 in 26534e7

	;; ty has to include exact 0, exact 1, null (sum/product/list respectively),
	;; the initial value of the accumulator
	;; (to be consistent with Racket semantics).
	;; We can't just change the initial value to be 0.0 if we expect a
	;; Float result. This is problematic in some cases e.g:
	;; (for/sum: : Float ([i : Float '(1.1)] #:when (zero? (random 1))) i)

typed-racket/typed-racket-lib/typed-racket/base-env/prims.rkt

Line 553 in 26534e7

(for*/sum: for*/fold: for*/sum #t + 0 #%expression)

My current workaround is to just use a foldl for now to avoid mangling Real and Float conversions in my actual program. Just making sure I'm not missing an obvious approach.

[samth]

Unfortunately this is the racket semantics for for/sum, so this is not fixable.