Issue with offset functions

[JAnthelme]

I'm on diagrams-lib 1.3.0.9 (Ubuntu Trusty 64bit). Using ghci (ghc version 7.10.2).

When trying to produce an offset from a bézier segment for which the first control point is identical to the first end point (i.e. in the function bezier3 c1 c2 x, using (V2 0.0 0.0) as c1), I get in an "infinite loop" at runtime, resulting in a stack overflow.

In the code below, replacing c1 by (V2 0.0 0.0), instead of (V2 0.0 1.0) for example, produces a run-time error when running main.

{-# LANGUAGE NoMonomorphismRestriction #-}
{-# LANGUAGE TypeFamilies              #-}
{-# LANGUAGE FlexibleContexts          #-}

import Diagrams.Backend.SVG
import Diagrams.Prelude

import Diagrams.TwoD.Offset (offsetTrail)

x2      = r2 (1.0,1.0) :: V2 Double    -- endpoint

-- this works well
[c1,c2] = map r2 [(0.0, 1.0), (1.0, 0.0)]    -- control points

-- this creates a run-time error (comment-out line 13, and uncomment line 16 to check).
-- [c1,c2] = map r2 [(0.0, 1.0), (1.0, 0.0)]    -- control points

t   = fromSegments [bézier3 c1 c2 x2]
t'  = (strokeLocTrail $ offsetTrail 0.5 t) # lc orange # lw thick

out = t <> t' # showOrigin

main = do
    let fp   = "./mySVG.svg"
        dims = mkSizeSpec2D (Just (500)) (Just (500))

    renderSVG fp dims (out :: Diagram B)

[byorgey]

Thanks for the report! A stack overflow is definitely a bug. I suppose @fryguybob will have to take a look at this, though I think he is deep in paper-writing mode at the moment.