[gcc/devel/rust/master] Merge #1071

[gcc/devel/rust/master] Merge #1071

[Thomas Schwinge]

https://gcc.gnu.org/g:9011184f38a04f81ba3194b826bec3f30a11c07b

commit 9011184f38a04f81ba3194b826bec3f30a11c07b
Merge: f9c1a14dab4 73532817fd6
Author: bors[bot] <26634292+bors[bot]@users.noreply.github.com>
Date:   Thu Mar 31 09:56:35 2022 +0000

    Merge #1071
    
    1071: Allow transcribing of zero nodes in certain cases r=CohenArthur a=CohenArthur
    
    When expanding AST fragments containing multiple nodes, we must be aware
    that some cases allow expanding zero or more nodes. Any macro
    transcription that gets parsed as many nodes (ie any transcriber function that calls `parse_many`) needs to be able to parse zero of those nodes and still get expanded properly (basically, removed).
    
    Previously, this would cause a failure to lower the macro invocation which would remain as a child instead of getting stripped/erased.
    
    
    
    Co-authored-by: Arthur Cohen <arthur.cohen@embecosm.com>

Diff:

 gcc/rust/ast/rust-ast.h                |  3 +--
 gcc/rust/ast/rust-macro.h              |  2 +-
 gcc/rust/expand/rust-macro-builtins.cc |  2 +-
 gcc/rust/expand/rust-macro-expand.cc   | 38 +++++++++++++++++-----------------
 gcc/rust/expand/rust-macro-expand.h    |  4 ++--
 gcc/testsuite/rust/compile/macro41.rs  | 13 ++++++++++++
 6 files changed, 37 insertions(+), 25 deletions(-)