[experiment] first draft of init array syntax

[dingxiangfei2009]

This patch allows parsing of the syntax init [ v1, v2, v3, .. ] and certain level of type checking on HIR level.

See Draft RFC, under tracking rust-lang/lang-team#336

Dragons ahead

This is a draft PR that is very experimental and it is posted only for very early feedback and it is not immediately mergeable.

• This patch introduces changes to the parser to accept init # ... AST fragment as a start.
  The reason that this deviates from the original proposal, with the additional #, is to help with syntax ambiguity between init[0] as indexing into a value init, versus init [ 0 ] as in-place initialisation.
  However, I would propose to switch to a macro based approach to the syntax to avoid such ambiguity.
• This patch introduces a new type category Init. It has the same generics structure as a Closure and it is almost type-checked in the same way as Closure, except that its return type expectation also contains the error type, which is to be unified with those from the nested in-place initialisation.
  This is still not functional, because for instance I still have to fill out some tables such as late_bound_vars.

This patch does not include any THIR or MIR building.

The final state at which I would see this patch can be merged, is to at least we can type check the following smoke test.

#![feature(in_place_initialization)]
use std::init::Init;

fn smoke() -> impl Init<[i32; 1]> {
    init # [0]
}

fn main() {}

Areas to improve

As of July 7th, I see that I need to work these out

• The AST node InitTail is not necessary, I should just drop it
• The HIR node InitKind::Array could be squashed so that it is just a list of InitTail nodes I start to appreciate this choice now because the HIR visitor would be a bit harder to write if I would decide to squash it.
• The HIR node names. I don't find them descriptive. InitTail sounds terrible and I regret the choice.

r? @compiler-errors

[bors]

☔ The latest upstream changes (presumably #143582) made this pull request unmergeable. Please resolve the merge conflicts.

[bors]

☔ The latest upstream changes (presumably #143538) made this pull request unmergeable. Please resolve the merge conflicts.

[rust-log-analyzer]

The job aarch64-gnu-llvm-19-1 failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)

---- [debuginfo-gdb] tests/debuginfo/function-names.rs stdout ----
NOTE: compiletest thinks it is using GDB version 15001000

error: check directive(s) from `/checkout/tests/debuginfo/function-names.rs` not found in debugger output. errors:
    (function-names.rs:40) `[...]static fn function_names::const_generic_fn_non_int<{CONST#ffa3db4ca1d52dce}>();`
the following subset of check directive(s) was found successfully:
    (function-names.rs:10) `90: static fn function_names::main();`
    (function-names.rs:12) `192: static fn function_names::generic_func<i32>(i32) -> i32;`
    (function-names.rs:16) `160: static fn function_names::GenericStruct<i32, i32>::impl_function<i32, i32>();`
    (function-names.rs:17) `148: static fn function_names::Mod1::TestStruct2::impl_function();`
    (function-names.rs:18) `132: static fn function_names::TestStruct1::impl_function();`
    (function-names.rs:22) `152: static fn function_names::Mod1::{impl#1}::trait_function();`
    (function-names.rs:23) `137: static fn function_names::{impl#1}::trait_function();`
    (function-names.rs:24) `169: static fn function_names::{impl#3}::trait_function<i32>();`
    (function-names.rs:25) `183: static fn function_names::{impl#5}::trait_function3<function_names::TestStruct1>();`
    (function-names.rs:26) `188: static fn function_names::{impl#6}::trait_function<i32, 1>();`
    (function-names.rs:30) `194: static fn function_names::generic_func::{closure#0}<i32>(*mut function_names::generic_func::{closure_env#0}<i32>);`
    (function-names.rs:31) `107: static fn function_names::main::{closure#0}(*mut function_names::main::{closure_env#0});`
    (function-names.rs:32) `162: static fn function_names::{impl#2}::impl_function::{closure#0}<i32, i32>(*mut function_names::{impl#2}::impl_function::{closure_env#0}<i32, i32>);`
    (function-names.rs:39) `200: static fn function_names::const_generic_fn_bool<false>();`
    (function-names.rs:41) `202: static fn function_names::const_generic_fn_signed_int<-7>();`
    (function-names.rs:42) `203: static fn function_names::const_generic_fn_unsigned_int<14>();`
status: exit status: 0
command: PYTHONPATH="/checkout/src/etc" "/usr/bin/gdb" "-quiet" "-batch" "-nx" "-command=/checkout/obj/build/aarch64-unknown-linux-gnu/test/debuginfo/function-names.gdb/function-names.debugger.script"
--- stdout -------------------------------
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File /checkout/tests/debuginfo/function-names.rs:
90: static fn function_names::main();
107: static fn function_names::main::{closure#0}(*mut function_names::main::{closure_env#0});
112: static fn function_names::main::{coroutine#1}(core::pin::Pin<&mut function_names::main::{coroutine_env#1}>, ()) -> core::ops::coroutine::CoroutineState<(), ()>;

File /rustc/FAKE_PREFIX/library/core/src/ptr/mod.rs:
804: static fn core::ptr::drop_in_place<function_names::main::{coroutine_env#1}>(*mut function_names::main::{coroutine_env#1});

File /checkout/tests/debuginfo/function-names.rs:
194: static fn function_names::generic_func::{closure#0}<i32>(*mut function_names::generic_func::{closure_env#0}<i32>);
192: static fn function_names::generic_func<i32>(i32) -> i32;

File /checkout/tests/debuginfo/function-names.rs:
160: static fn function_names::GenericStruct<i32, i32>::impl_function<i32, i32>();
148: static fn function_names::Mod1::TestStruct2::impl_function();
132: static fn function_names::TestStruct1::impl_function();
162: static fn function_names::{impl#2}::impl_function::{closure#0}<i32, i32>(*mut function_names::{impl#2}::impl_function::{closure_env#0}<i32, i32>);

File /checkout/tests/debuginfo/function-names.rs:
152: static fn function_names::Mod1::{impl#1}::trait_function();
137: static fn function_names::{impl#1}::trait_function();
169: static fn function_names::{impl#3}::trait_function<i32>();
183: static fn function_names::{impl#5}::trait_function3<function_names::TestStruct1>();
188: static fn function_names::{impl#6}::trait_function<i32, 1>();

File /checkout/tests/debuginfo/function-names.rs:
194: static fn function_names::generic_func::{closure#0}<i32>(*mut function_names::generic_func::{closure_env#0}<i32>);
107: static fn function_names::main::{closure#0}(*mut function_names::main::{closure_env#0});
162: static fn function_names::{impl#2}::impl_function::{closure#0}<i32, i32>(*mut function_names::{impl#2}::impl_function::{closure_env#0}<i32, i32>);

File /checkout/tests/debuginfo/function-names.rs:
200: static fn function_names::const_generic_fn_bool<false>();
201: static fn function_names::const_generic_fn_non_int<{CONST#5177fe61e1757625}>();
202: static fn function_names::const_generic_fn_signed_int<-7>();
203: static fn function_names::const_generic_fn_unsigned_int<14>();
------------------------------------------
stderr: none

[bors]

☔ The latest upstream changes (presumably #144440) made this pull request unmergeable. Please resolve the merge conflicts.

[dingxiangfei2009]

Standby.

I have working on the feedbacks on the language design.