Rewrite the Rust expression parser
The Rust expression parser was written to construct its own AST, then
lower this to GDB expressions. I did this primarily because the old
expressions were difficult to work with; after rewriting those, I
realized I could remove the AST from the Rust parser.
After looking at this, I realized it might be simpler to rewrite the
parser. This patch reimplements it as a recursive-descent parser. I
kept a fair amount of the existing code -- the lexer is pulled in
nearly unchanged.
There are several benefits to this approach:
* The parser is shorter now (from 2882 LOC to 2351).
* The parser is just ordinary C++ code that can be debugged in the
usual way.
* Memory management in the parser is now straightforward, as
parsing methods simply return a unique pointer or vector.
This required a couple of minor changes to the test suite, as some
errors have changed.
While this passes the tests, it's possible there are lurking bugs,
particularly around error handling.
gdb/ChangeLog
2021-04-16 Tom Tromey <tom@tromey.com>
* rust-parse.c: New file.
* rust-exp.y: Remove.
* Makefile.in (COMMON_SFILES): Add rust-parse.c.
(SFILES): Remove rust-exp.y.
(YYFILES, local-maintainer-clean): Remove rust-exp.c.
gdb/testsuite/ChangeLog
2021-04-16 Tom Tromey <tom@tromey.com>
* gdb.rust/simple.exp: Change error text.
* gdb.rust/expr.exp: Change error text.