Add warn(unreachable_pub) to rustc_expand.

Plus a tiny bit of reformatting.

compiler/rustc_expand/src/errors.rs

@@ -350,7 +350,7 @@ pub(crate) struct ModuleMultipleCandidates {
 
 #[derive(Diagnostic)]
 #[diag(expand_trace_macro)]
-pub struct TraceMacro {
+pub(crate) struct TraceMacro {
     #[primary_span]
     pub span: Span,
 }
@@ -402,14 +402,14 @@ pub(crate) struct CustomAttributePanickedHelp {
 
 #[derive(Diagnostic)]
 #[diag(expand_proc_macro_derive_tokens)]
-pub struct ProcMacroDeriveTokens {
+pub(crate) struct ProcMacroDeriveTokens {
     #[primary_span]
     pub span: Span,
 }
 
 #[derive(Diagnostic)]
 #[diag(expand_duplicate_matcher_binding)]
-pub struct DuplicateMatcherBinding {
+pub(crate) struct DuplicateMatcherBinding {
     #[primary_span]
     #[label]
     pub span: Span,
@@ -421,7 +421,7 @@ pub struct DuplicateMatcherBinding {
 #[diag(expand_missing_fragment_specifier)]
 #[note]
 #[help(expand_valid)]
-pub struct MissingFragmentSpecifier {
+pub(crate) struct MissingFragmentSpecifier {
     #[primary_span]
     pub span: Span,
     #[suggestion(
@@ -437,7 +437,7 @@ pub struct MissingFragmentSpecifier {
 #[derive(Diagnostic)]
 #[diag(expand_invalid_fragment_specifier)]
 #[help]
-pub struct InvalidFragmentSpecifier {
+pub(crate) struct InvalidFragmentSpecifier {
     #[primary_span]
     pub span: Span,
     pub fragment: Ident,
@@ -446,7 +446,7 @@ pub struct InvalidFragmentSpecifier {
 
 #[derive(Diagnostic)]
 #[diag(expand_expected_paren_or_brace)]
-pub struct ExpectedParenOrBrace<'a> {
+pub(crate) struct ExpectedParenOrBrace<'a> {
     #[primary_span]
     pub span: Span,
     pub token: Cow<'a, str>,
@@ -479,7 +479,7 @@ pub(crate) struct GlobDelegationTraitlessQpath {
 #[derive(Diagnostic)]
 #[diag(expand_proc_macro_back_compat)]
 #[note]
-pub struct ProcMacroBackCompat {
+pub(crate) struct ProcMacroBackCompat {
     pub crate_name: String,
     pub fixed_version: String,
 }

compiler/rustc_expand/src/lib.rs

@@ -13,6 +13,7 @@
 #![feature(rustdoc_internals)]
 #![feature(try_blocks)]
 #![feature(yeet_expr)]
+#![warn(unreachable_pub)]
 // tidy-alphabetical-end
 
 extern crate proc_macro as pm;

compiler/rustc_expand/src/mbe/diagnostics.rs

@@ -196,13 +196,14 @@ impl<'dcx> CollectTrackerAndEmitter<'dcx, '_> {
     }
 }
 
-/// Currently used by macro_rules! compilation to extract a little information from the `Failure` case.
-pub struct FailureForwarder<'matcher> {
+/// Currently used by macro_rules! compilation to extract a little information from the `Failure`
+/// case.
+pub(crate) struct FailureForwarder<'matcher> {
     expected_token: Option<&'matcher Token>,
 }
 
 impl<'matcher> FailureForwarder<'matcher> {
-    pub fn new() -> Self {
+    pub(crate) fn new() -> Self {
         Self { expected_token: None }
     }
 }

compiler/rustc_expand/src/mbe/macro_parser.rs

@@ -407,7 +407,7 @@ fn token_name_eq(t1: &Token, t2: &Token) -> bool {
 
 // Note: the vectors could be created and dropped within `parse_tt`, but to avoid excess
 // allocations we have a single vector for each kind that is cleared and reused repeatedly.
-pub struct TtParser {
+pub(crate) struct TtParser {
     macro_name: Ident,
 
     /// The set of current mps to be processed. This should be empty by the end of a successful

compiler/rustc_expand/src/mbe/quoted.rs

@@ -14,12 +14,11 @@ use crate::mbe::macro_parser::count_metavar_decls;
 use crate::mbe::{Delimited, KleeneOp, KleeneToken, MetaVarExpr, SequenceRepetition, TokenTree};
 
 const VALID_FRAGMENT_NAMES_MSG: &str = "valid fragment specifiers are \
-                                        `ident`, `block`, `stmt`, `expr`, `pat`, `ty`, `lifetime`, \
-                                        `literal`, `path`, `meta`, `tt`, `item` and `vis`";
-pub const VALID_FRAGMENT_NAMES_MSG_2021: &str = "valid fragment specifiers are \
-                                             `ident`, `block`, `stmt`, `expr`, `expr_2021`, `pat`, \
-                                             `ty`, `lifetime`, `literal`, `path`, `meta`, `tt`, \
+    `ident`, `block`, `stmt`, `expr`, `pat`, `ty`, `lifetime`, `literal`, `path`, `meta`, `tt`, \
     `item` and `vis`";
+pub(crate) const VALID_FRAGMENT_NAMES_MSG_2021: &str = "valid fragment specifiers are \
+    `ident`, `block`, `stmt`, `expr`, `expr_2021`, `pat`, `ty`, `lifetime`, `literal`, `path`, \
+    `meta`, `tt`, `item` and `vis`";
 
 /// Takes a `tokenstream::TokenStream` and returns a `Vec<self::TokenTree>`. Specifically, this
 /// takes a generic `TokenStream`, such as is used in the rest of the compiler, and returns a

compiler/rustc_expand/src/placeholders.rs

@@ -191,12 +191,12 @@ pub(crate) fn placeholder(
 }
 
 #[derive(Default)]
-pub struct PlaceholderExpander {
+pub(crate) struct PlaceholderExpander {
     expanded_fragments: FxHashMap<ast::NodeId, AstFragment>,
 }
 
 impl PlaceholderExpander {
-    pub fn add(&mut self, id: ast::NodeId, mut fragment: AstFragment) {
+    pub(crate) fn add(&mut self, id: ast::NodeId, mut fragment: AstFragment) {
         fragment.mut_visit_with(self);
         self.expanded_fragments.insert(id, fragment);
     }

compiler/rustc_expand/src/proc_macro_server.rs

@@ -414,7 +414,7 @@ impl ToInternal<rustc_errors::Level> for Level {
     }
 }
 
-pub struct FreeFunctions;
+pub(crate) struct FreeFunctions;
 
 pub(crate) struct Rustc<'a, 'b> {
     ecx: &'a mut ExtCtxt<'b>,
@@ -426,7 +426,7 @@ pub(crate) struct Rustc<'a, 'b> {
 }
 
 impl<'a, 'b> Rustc<'a, 'b> {
-    pub fn new(ecx: &'a mut ExtCtxt<'b>) -> Self {
+    pub(crate) fn new(ecx: &'a mut ExtCtxt<'b>) -> Self {
         let expn_data = ecx.current_expansion.id.expn_data();
         Rustc {
             def_site: ecx.with_def_site_ctxt(expn_data.def_site),