Rest placement following use of Temporary Polyphonic Context is wrong

[Guy Stalnaker]

I noticed this recently but did not have time to post to the list. Now I 
do so here 'tis.

I checked the docs and in the section on TPC 
(http://www.lilypond.org/doc/v2.18/Documentation/notation/multiple-voices#single_002dstaff-polyphony) 
I see no note or warning that what I see is "expected". What do I see? 
If I set some measures with rests followed by some notes, followed by 
two voices set using the TPC syntax ( << \voiceOne {} \new Voice { 
\voiceTwo } >> \voiceOne ), following the conclusion of the TPC section, 
subsequent rests are engraved as if two voices still exist, as if (I 
pray I'm using the correct terminology) the "temporary context" has not 
been removed, i.e., it was not temporary and continues to influence the 
engraving of the staff.

Is there a "purge" or "clean" or "clear" or "release" command one might 
use to fix this? In the past I've used manual rest placement to move 
them where they should be, but I should not need to do that. The rest 
placement remains incorrect whether I use \voiceTwo or \voiceFour for 
the \new Voice in the TPC.

Here's some test music that shows what I'm seeing.

<code>
\version "2.16.0"
\language "english"
\header {
  title = "Rest placement error?"
  subtitle = "After Temporary Polyphonic Context"
  subsubtitle = "Rests appear as if for upper voice"
}
global = {
  \key c \major
  \time 3/4
}
sopranoVoice =  {
  \global
  \dynamicUp
  \partial 4 r4 |
  r2.^\markup {Rests where they are supposed to be} |
  r |
  r |
  r \bar "||"
  g'4 \mp ^\markup {Calmly} a'8 a' b'4 |
  c''4. d''8 c''4 |
  b'8[ g'] g'[ b'] d''4 |
  e''8 c'' d''2 |
  << \voiceOne { d''4 g''8[ fs''] e''( d'') |
               c''8 c'' d''4( e'') |
               f''4 a' c'' |
               d''2 c''4 |
               c''2. ~ |
               c''2. }
   \new Voice { \voiceTwo d''4 ^\markup { TPC starts here} b'8 a' g'4 |
                a'8 a' b'4( c''8 b') |
                a'4 f' a' |
                b'2 c''4 |
                c''2. ~ |
                c''2. } >> \voiceOne |
  r ^\markup {Error here - acts like there are two voices!} |
  r |
  r |
  r |
  r |
}
sopranoVoicePart = \new Staff \with {
  instrumentName = "S."
  midiInstrument = "clarinet"
} { \sopranoVoice }
\score {
  <<
    \sopranoVoicePart
  >>
  \layout { }
  \midi { }
}
</code>

--
"There is only love, and then oblivion. Love is all we have
to set against hatred." (paraphrased) Ian McEwan

Guy Stalnaker
address@hidden