Auto merge of #116477 - nnethercote:tidy-alpha-deps, r=wesleywiser

Use tidy to enforce alphabetical dependency ordering

I get annoyed when dependencies in `Cargo.toml` files are not in alphabetical order. The [style guide](https://github.com/rust-lang/rust/blob/master/src/doc/style-guide/src/cargo.md) agrees with me.

There are ongoing efforts to provide linting/formatting of `Cargo.toml` files, e.g. rust-lang/rustfmt#5240, https://crates.io/crates/cargo-toml-lint, and https://github.com/TimonPost/cargo-toml-format. But it's far from clear what's the right approach.

So this PR does something very simple: it uses the order checking already present in tidy. This allows incremental application of ordering, starting right now, and avoiding the need for any kind of all-at-once conversion.

If we do end up using some more comprehensive `Cargo.toml` linting/formatting solution in the future, the `tidy-alphabetical` lines will be easy to remove.

r? `@wesleywiser`

compiler/rustc_driver_impl/Cargo.toml

@@ -6,53 +6,55 @@ edition = "2021"
 [lib]
 
 [dependencies]
-time = { version = "0.3", default-features = false, features = ["formatting", ] }
-tracing = { version = "0.1.35" }
-serde_json = "1.0.59"
-rustc_log = { path = "../rustc_log" }
+# tidy-alphabetical-start
+rustc_ast = { path = "../rustc_ast" }
 rustc_ast_lowering = { path = "../rustc_ast_lowering" }
 rustc_ast_passes = { path = "../rustc_ast_passes" }
+rustc_ast_pretty = { path = "../rustc_ast_pretty" }
 rustc_attr = { path = "../rustc_attr" }
 rustc_borrowck = { path = "../rustc_borrowck" }
 rustc_builtin_macros = { path = "../rustc_builtin_macros" }
+rustc_codegen_ssa = { path = "../rustc_codegen_ssa" }
 rustc_const_eval = { path = "../rustc_const_eval" }
+rustc_data_structures = { path = "../rustc_data_structures" }
+rustc_error_codes = { path = "../rustc_error_codes" }
 rustc_error_messages = { path = "../rustc_error_messages" }
+rustc_errors = { path = "../rustc_errors" }
 rustc_expand = { path = "../rustc_expand" }
-rustc_hir_typeck = { path = "../rustc_hir_typeck" }
+rustc_feature = { path = "../rustc_feature" }
 rustc_fluent_macro = { path = "../rustc_fluent_macro" }
+rustc_hir = { path = "../rustc_hir" }
+rustc_hir_analysis = { path = "../rustc_hir_analysis" }
+rustc_hir_pretty = { path = "../rustc_hir_pretty" }
+rustc_hir_typeck = { path = "../rustc_hir_typeck" }
 rustc_incremental = { path = "../rustc_incremental" }
 rustc_infer = { path = "../rustc_infer" }
+rustc_interface = { path = "../rustc_interface" }
+rustc_lint = { path = "../rustc_lint" }
+rustc_log = { path = "../rustc_log" }
+rustc_macros = { path = "../rustc_macros" }
+rustc_metadata = { path = "../rustc_metadata" }
+rustc_middle = { path = "../rustc_middle" }
 rustc_mir_build = { path = "../rustc_mir_build" }
 rustc_mir_dataflow = { path = "../rustc_mir_dataflow" }
+rustc_mir_transform = { path = "../rustc_mir_transform" }
 rustc_monomorphize = { path = "../rustc_monomorphize" }
+rustc_parse = { path = "../rustc_parse" }
 rustc_passes = { path = "../rustc_passes" }
+rustc_plugin_impl = { path = "../rustc_plugin_impl" }
 rustc_privacy = { path = "../rustc_privacy" }
 rustc_query_system = { path = "../rustc_query_system" }
 rustc_resolve = { path = "../rustc_resolve" }
+rustc_session = { path = "../rustc_session" }
+rustc_span = { path = "../rustc_span" }
 rustc_symbol_mangling = { path = "../rustc_symbol_mangling" }
+rustc_target = { path = "../rustc_target" }
 rustc_trait_selection = { path = "../rustc_trait_selection" }
 rustc_ty_utils = { path = "../rustc_ty_utils" }
-rustc_middle = { path = "../rustc_middle" }
-rustc_ast_pretty = { path = "../rustc_ast_pretty" }
-rustc_target = { path = "../rustc_target" }
-rustc_lint = { path = "../rustc_lint" }
-rustc_data_structures = { path = "../rustc_data_structures" }
-rustc_errors = { path = "../rustc_errors" }
-rustc_feature = { path = "../rustc_feature" }
-rustc_hir = { path = "../rustc_hir" }
-rustc_hir_pretty = { path = "../rustc_hir_pretty" }
-rustc_macros = { path = "../rustc_macros" }
-rustc_metadata = { path = "../rustc_metadata" }
-rustc_parse = { path = "../rustc_parse" }
-rustc_plugin_impl = { path = "../rustc_plugin_impl" }
-rustc_codegen_ssa = { path = "../rustc_codegen_ssa" }
-rustc_session = { path = "../rustc_session" }
-rustc_error_codes = { path = "../rustc_error_codes" }
-rustc_interface = { path = "../rustc_interface" }
-rustc_ast = { path = "../rustc_ast" }
-rustc_span = { path = "../rustc_span" }
-rustc_hir_analysis = { path = "../rustc_hir_analysis" }
-rustc_mir_transform = { path = "../rustc_mir_transform" }
+serde_json = "1.0.59"
+time = { version = "0.3", default-features = false, features = ["formatting", ] }
+tracing = { version = "0.1.35" }
+# tidy-alphabetical-end
 
 [target.'cfg(unix)'.dependencies]
 libc = "0.2"

src/tools/tidy/src/alphabetical.rs

@@ -30,8 +30,8 @@ fn is_close_bracket(c: char) -> bool {
 }
 
 // Don't let tidy check this here :D
-const START_COMMENT: &str = concat!("// tidy-alphabetical", "-start");
-const END_COMMENT: &str = "// tidy-alphabetical-end";
+const START_COMMENT: &str = concat!("tidy-alphabetical", "-start");
+const END_COMMENT: &str = "tidy-alphabetical-end";
 
 fn check_section<'a>(
     file: impl Display,