[gcc/devel/rust/master] Merge #1040

[Thomas Schwinge <tschwinge@gcc.gnu.org>]

https://gcc.gnu.org/g:6ecd43c7797eb287f15d64f80f4654361c046f4a

commit 6ecd43c7797eb287f15d64f80f4654361c046f4a
Merge: 32894e69865 a64a5cf77c9
Author: bors[bot] <26634292+bors[bot]@users.noreply.github.com>
Date:   Tue Mar 22 11:02:45 2022 +0000

    Merge #1040
    
    1040: Do not propagate parse errors in match repetitions r=CohenArthur a=CohenArthur
    
    Since parsing repetitions is very eager, the parser might accumulate
    bogus errors by trying to match more repetitions than there are. We can
    avoid this by clearing the parsing errors if parsing repetitions
    returned a valid result. This should not be an issue for previous
    matchers erroring out, as they would immediately return upon failure and
    not reach inside other match functions.
    
    We need to figure out the best way to emit parser errors, as we do not always want to emit them in `match_fragment`. I think for now the easiest is to just *not* emit parse errors and simply error out with "failed to match macro rule". We will need to think about adding a bunch of hints too in order to make using macros easier.
    
    Fixes #958
    
    Co-authored-by: Arthur Cohen <arthur.cohen@embecosm.com>

Diff:

 gcc/rust/expand/rust-macro-expand.cc  | 11 +++++++----
 gcc/rust/parse/rust-parse.h           |  3 ++-
 gcc/testsuite/rust/compile/macro25.rs |  9 +++++++++
 gcc/testsuite/rust/compile/macro9.rs  |  1 -
 4 files changed, 18 insertions(+), 6 deletions(-)