Example session:
```
» 1 + 1
The Roc compiler had an internal error.
Please file a bug report at
https://github.com/roc-lang/roc/issues/new
Please include the following data:
Error message: intentional panic
Stack backtrace:
0: std::backtrace_rs::backtrace::libunwind::trace
at /rustc/25ef9e3d85d934b27d9dada2f9dd52b1dc63bb04/library/std/src/../../backtrace/src/backtrace/libunwind.rs:104:5
1: std::backtrace_rs::backtrace::trace_unsynchronized
at /rustc/25ef9e3d85d934b27d9dada2f9dd52b1dc63bb04/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
2: std::backtrace::Backtrace::create
at /rustc/25ef9e3d85d934b27d9dada2f9dd52b1dc63bb04/library/std/src/backtrace.rs:331:13
3: panic_hook
at ./crates/repl_cli/src/lib.rs:52:41
4: call<fn(&core::panic::panic_info::PanicInfo), (&core::panic::panic_info::PanicInfo)>
at /rustc/25ef9e3d85d934b27d9dada2f9dd52b1dc63bb04/library/core/src/ops/function.rs:79:5
5: <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call
at /rustc/25ef9e3d85d934b27d9dada2f9dd52b1dc63bb04/library/alloc/src/boxed.rs:2029:9
6: std::panicking::rust_panic_with_hook
at /rustc/25ef9e3d85d934b27d9dada2f9dd52b1dc63bb04/library/std/src/panicking.rs:785:13
7: std::panicking::begin_panic_handler::{{closure}}
at /rustc/25ef9e3d85d934b27d9dada2f9dd52b1dc63bb04/library/std/src/panicking.rs:651:13
8: std::sys_common::backtrace::__rust_end_short_backtrace
at /rustc/25ef9e3d85d934b27d9dada2f9dd52b1dc63bb04/library/std/src/sys_common/backtrace.rs:171:18
9: rust_begin_unwind
at /rustc/25ef9e3d85d934b27d9dada2f9dd52b1dc63bb04/library/std/src/panicking.rs:647:5
10: core::panicking::panic_fmt
at /rustc/25ef9e3d85d934b27d9dada2f9dd52b1dc63bb04/library/core/src/panicking.rs:72:14
11: step
at ./crates/repl_ui/src/repl_state.rs:66:9
12: {closure#1}
at ./crates/repl_cli/src/lib.rs:109:21
13: call_once<roc_repl_cli::main::{closure_env#1}, ()>
at /rustc/25ef9e3d85d934b27d9dada2f9dd52b1dc63bb04/library/core/src/ops/function.rs:250:5
14: call_once<roc_repl_ui::repl_state::ReplAction, roc_repl_cli::main::{closure_env#1}>
at /rustc/25ef9e3d85d934b27d9dada2f9dd52b1dc63bb04/library/core/src/panic/unwind_safe.rs:272:9
15: do_call<core::panic::unwind_safe::AssertUnwindSafe<roc_repl_cli::main::{closure_env#1}>, roc_repl_ui::repl_state::ReplAction>
at /rustc/25ef9e3d85d934b27d9dada2f9dd52b1dc63bb04/library/std/src/panicking.rs:554:40
16: ___rust_try
17: try<roc_repl_ui::repl_state::ReplAction, core::panic::unwind_safe::AssertUnwindSafe<roc_repl_cli::main::{closure_env#1}>>
at /rustc/25ef9e3d85d934b27d9dada2f9dd52b1dc63bb04/library/std/src/panicking.rs:518:19
18: catch_unwind<core::panic::unwind_safe::AssertUnwindSafe<roc_repl_cli::main::{closure_env#1}>, roc_repl_ui::repl_state::ReplAction>
at /rustc/25ef9e3d85d934b27d9dada2f9dd52b1dc63bb04/library/std/src/panic.rs:142:14
19: main
at ./crates/repl_cli/src/lib.rs:108:30
20: main
at ./crates/cli/src/main.rs:321:16
21: call_once<fn() -> core::result::Result<(), std::io::error::Error>, ()>
at /rustc/25ef9e3d85d934b27d9dada2f9dd52b1dc63bb04/library/core/src/ops/function.rs:250:5
22: __rust_begin_short_backtrace<fn() -> core::result::Result<(), std::io::error::Error>, core::result::Result<(), std::io::error::Error>>
at /rustc/25ef9e3d85d934b27d9dada2f9dd52b1dc63bb04/library/std/src/sys_common/backtrace.rs:155:18
23: {closure#0}<core::result::Result<(), std::io::error::Error>>
at /rustc/25ef9e3d85d934b27d9dada2f9dd52b1dc63bb04/library/std/src/rt.rs:166:18
24: core::ops::function::impls::<impl core::ops::function::FnOnce<A> for &F>::call_once
at /rustc/25ef9e3d85d934b27d9dada2f9dd52b1dc63bb04/library/core/src/ops/function.rs:284:13
25: std::panicking::try::do_call
at /rustc/25ef9e3d85d934b27d9dada2f9dd52b1dc63bb04/library/std/src/panicking.rs:554:40
26: std::panicking::try
at /rustc/25ef9e3d85d934b27d9dada2f9dd52b1dc63bb04/library/std/src/panicking.rs:518:19
27: std::panic::catch_unwind
at /rustc/25ef9e3d85d934b27d9dada2f9dd52b1dc63bb04/library/std/src/panic.rs:142:14
28: std::rt::lang_start_internal::{{closure}}
at /rustc/25ef9e3d85d934b27d9dada2f9dd52b1dc63bb04/library/std/src/rt.rs:148:48
29: std::panicking::try::do_call
at /rustc/25ef9e3d85d934b27d9dada2f9dd52b1dc63bb04/library/std/src/panicking.rs:554:40
30: std::panicking::try
at /rustc/25ef9e3d85d934b27d9dada2f9dd52b1dc63bb04/library/std/src/panicking.rs:518:19
31: std::panic::catch_unwind
at /rustc/25ef9e3d85d934b27d9dada2f9dd52b1dc63bb04/library/std/src/panic.rs:142:14
32: std::rt::lang_start_internal
at /rustc/25ef9e3d85d934b27d9dada2f9dd52b1dc63bb04/library/std/src/rt.rs:148:20
33: lang_start<core::result::Result<(), std::io::error::Error>>
at /rustc/25ef9e3d85d934b27d9dada2f9dd52b1dc63bb04/library/std/src/rt.rs:165:17
34: _main
Machine Target: MacArm64
```
This removes the need to explicitly pass thru min_indent when using the parser combinators.
My ultimate goal here is to evolve the current parser closer toward a purely combinator-based parser,
at which point we can more easily transition smoothly to a formal(ish) grammar, or expand the meanings of combinators
to include things like:
* Incremental (re)parsing
* Unified parsing and formatting code
* Better error recovery
* Using the main parser directly for syntax highlighting
Adds a thread-local interner of layouts to LayoutCache, and updates all
references appropriately.
This is a bit suboptimal for single-threaded workloads that will look at
creating layout caches again, like the REPL, but I think that's okay for
now - since the global interner will be uncontested for those workloads, it
should still be plenty fast to access the interner, even behind a lock.
