Fix lookup of TuplePattern sub-pattern types

[powerboat9]

Fixes the issue pointed out in this comment.

[CohenArthur]

LGTM, thanks :) can you change your PR's main comment so that #2847 isn't closed by this PR? the original code still causes an ICE

[powerboat9]

It looks like I managed to fix it

[CohenArthur]

I checked out your commit and still get an ICE for the original testcase:

arthur@platypus ~/G/r/gccrs ((b8d8b5f9)) [1]> git log -1
commit b8d8b5f95625bbaa437fd167a57f4b0fe81b43e7 (HEAD, powerboat9/fix-let-u)
Author: Owen Avery <powerboat9.gamer@gmail.com>
Date:   Mon Feb 12 18:20:19 2024 -0500

    Fix lookup of TuplePattern sub-pattern types

    gcc/rust/ChangeLog:

            * backend/rust-compile-pattern.cc
            (CompilePatternLet::visit):
            Lookup type of sub-pattern, not tuple pattern itself.

    gcc/testsuite/ChangeLog:

            * rust/compile/issue-2847-b.rs: New test.

    Signed-off-by: Owen Avery <powerboat9.gamer@gmail.com>
arthur@platypus ~/G/r/gccrs ((b8d8b5f9))> cat test.rs
fn myfun((x, _): (i32, i32)) -> i32 {
    x
}
arthur@platypus ~/G/r/gccrs ((b8d8b5f9))> build/gcc/crab1 test.rs
crab1: internal compiler error: in function_set_parameters, at rust/rust-gcc.cc:2284
0x1f448bf Backend::function_set_parameters(tree_node*, std::vector<Bvariable*, std::allocator<Bvariable*> > const&)
	/home/arthur/Git/rust-gcc/gccrs/build/gcc/../../gcc/rust/rust-gcc.cc:2284
0x24345a7 Rust::Compile::HIRCompileBase::compile_function(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, Rust::HIR::SelfParam&, std::vector<Rust::HIR::FunctionParam, std::allocator<Rust::HIR::FunctionParam> >&, Rust::HIR::FunctionQualifiers const&, Rust::HIR::Visibility&, std::vector<Rust::AST::Attribute, std::allocator<Rust::AST::Attribute> >&, unsigned int, Rust::HIR::BlockExpr*, Rust::Resolver::CanonicalPath const*, Rust::TyTy::FnType*)
	/home/arthur/Git/rust-gcc/gccrs/build/gcc/../../gcc/rust/backend/rust-compile-base.cc:721
0x23f48bf Rust::Compile::CompileItem::visit(Rust::HIR::Function&)
	/home/arthur/Git/rust-gcc/gccrs/build/gcc/../../gcc/rust/backend/rust-compile-item.cc:179
0x21e2f5d Rust::HIR::Function::accept_vis(Rust::HIR::HIRStmtVisitor&)
	/home/arthur/Git/rust-gcc/gccrs/build/gcc/../../gcc/rust/hir/tree/rust-hir.cc:4974
0x20ec894 Rust::Compile::CompileItem::compile(Rust::HIR::Item*, Rust::Compile::Context*, Rust::TyTy::BaseType*, bool, unsigned int)
	../../gcc/rust/backend/rust-compile-item.h:38
0x20ea940 Rust::Compile::CompileCrate::go()
	/home/arthur/Git/rust-gcc/gccrs/build/gcc/../../gcc/rust/backend/rust-compile.cc:48
0x20ea87a Rust::Compile::CompileCrate::Compile(Rust::HIR::Crate&, Rust::Compile::Context*)
	/home/arthur/Git/rust-gcc/gccrs/build/gcc/../../gcc/rust/backend/rust-compile.cc:41
0x20d3811 Rust::Session::compile_crate(char const*)
	/home/arthur/Git/rust-gcc/gccrs/build/gcc/../../gcc/rust/rust-session-manager.cc:694
0x20d2da1 Rust::Session::handle_input_files(int, char const**)
	/home/arthur/Git/rust-gcc/gccrs/build/gcc/../../gcc/rust/rust-session-manager.cc:408
0x1f25322 grs_langhook_parse_file()
	/home/arthur/Git/rust-gcc/gccrs/build/gcc/../../gcc/rust/rust-lang.cc:165
Please submit a full bug report, with preprocessed source (by using -freport-bug).
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.

[powerboat9]

I fixed the issue pointed out in the linked comment, which seems to be mostly unrelated to #2847 itself

fn myfun() -> i32 {
    let (x, _) =  (1, 2);
    x
}

[CohenArthur]

thanks :)