Lots of improvements.

* Better script names and grammar fix.
* Bump Rust
* Enforce more lints.
* Improve few struct definitions by removing box.
* Many minor implementation improvements.

src/lib.rs

@@ -1,44 +1,51 @@
 //! KECC: KAIST Educational C Compiler.
 
-// Tries to deny all lints (`rustc -W help`).
+#![deny(clippy::all)]
+#![deny(rustdoc::all)]
 #![deny(warnings)]
+// Tries to deny all rustc allow lints.
+// <https://doc.rust-lang.org/rustc/lints/listing/allowed-by-default.html>
 #![deny(absolute_paths_not_starting_with_crate)]
-#![deny(anonymous_parameters)]
+// Old, historical lint
 // #![deny(box_pointers)]
-#![deny(deprecated_in_future)]
 #![deny(elided_lifetimes_in_paths)]
 #![deny(explicit_outlives_requirements)]
-#![deny(rustdoc::invalid_html_tags)]
 #![deny(keyword_idents)]
+#![deny(let_underscore_drop)]
 #![deny(macro_use_extern_crate)]
+#![deny(meta_variable_misuse)]
+#![deny(missing_abi)]
+#![deny(missing_copy_implementations)]
 #![deny(missing_debug_implementations)]
-// #![deny(missing_docs)] TODO
-#![deny(rustdoc::missing_doc_code_examples)]
+// TODO
+// #![deny(missing_docs)]
 #![deny(non_ascii_idents)]
+#![deny(noop_method_call)]
 #![deny(pointer_structural_match)]
+#![deny(rust_2021_incompatible_closure_captures)]
+#![deny(rust_2021_incompatible_or_patterns)]
+#![deny(rust_2021_prefixes_incompatible_syntax)]
+#![deny(rust_2021_prelude_collisions)]
+// Necessary for skeleton code.
 // #![deny(single_use_lifetimes)]
+#![deny(trivial_casts)]
 #![deny(trivial_numeric_casts)]
-#![deny(unaligned_references)]
+// Necessary for skeleton code.
 // #![deny(unreachable_pub)]
+#![deny(unsafe_code)]
+#![deny(unsafe_op_in_unsafe_fn)]
 #![deny(unstable_features)]
 // Necessary for `build-bin` trick.
 // #![deny(unused_crate_dependencies)]
 #![deny(unused_extern_crates)]
 #![deny(unused_import_braces)]
 #![deny(unused_lifetimes)]
+#![deny(unused_macro_rules)]
 #![deny(unused_qualifications)]
 #![deny(unused_results)]
+#![deny(unused_tuple_struct_fields)]
+// Allowed for more flexible variants.
 // #![deny(variant_size_differences)]
-#![deny(rust_2018_idioms)]
-#![deny(rustdoc::all)]
-// Necessary for skeleton code.
-#![allow(unreachable_code)]
-// Necessary to allow `iter.fold(false, |l, r| l || r)`. It's used when iteration should not be
-// short-circuited.
-#![allow(clippy::unnecessary_fold)]
-#![allow(clippy::result_unit_err)]
-#![allow(clippy::vec_init_then_push)]
-#![allow(clippy::collapsible_match)]
 
 mod tests;
 mod utils;