Rollup merge of #146090 - Kobzol:invisible-origin-eq, r=petrochenkov

Derive `PartialEq` for `InvisibleOrigin`

For #145354, we need `PartialEq` for `TokenStream` to "just work". However, due to the special comparison implementation that was used for `InvisibleOrigin`, this wasn't the case.

So I derived `PartialEq` for `InvisibleOrigin`, and used the previous special comparison logic only on the single place where it was actually required.

r? ```````@petrochenkov```````

Author: Zalathar

compiler/rustc_ast/src/token.rs

@@ -22,8 +22,7 @@ pub enum CommentKind {
     Block,
 }
 
-// This type must not implement `Hash` due to the unusual `PartialEq` impl below.
-#[derive(Copy, Clone, Debug, Encodable, Decodable, HashStable_Generic)]
+#[derive(Copy, Clone, PartialEq, Debug, Encodable, Decodable, HashStable_Generic)]
 pub enum InvisibleOrigin {
     // From the expansion of a metavariable in a declarative macro.
     MetaVar(MetaVarKind),
@@ -45,20 +44,6 @@ impl InvisibleOrigin {
     }
 }
 
-impl PartialEq for InvisibleOrigin {
-    #[inline]
-    fn eq(&self, _other: &InvisibleOrigin) -> bool {
-        // When we had AST-based nonterminals we couldn't compare them, and the
-        // old `Nonterminal` type had an `eq` that always returned false,
-        // resulting in this restriction:
-        // https://doc.rust-lang.org/nightly/reference/macros-by-example.html#forwarding-a-matched-fragment
-        // This `eq` emulates that behaviour. We could consider lifting this
-        // restriction now but there are still cases involving invisible
-        // delimiters that make it harder than it first appears.
-        false
-    }
-}
-
 /// Annoyingly similar to `NonterminalKind`, but the slight differences are important.
 #[derive(Debug, Copy, Clone, PartialEq, Eq, Encodable, Decodable, Hash, HashStable_Generic)]
 pub enum MetaVarKind {
@@ -142,7 +127,8 @@ impl Delimiter {
         }
     }
 
-    // This exists because `InvisibleOrigin`s should be compared. It is only used for assertions.
+    // This exists because `InvisibleOrigin`s should not be compared. It is only used for
+    // assertions.
     pub fn eq_ignoring_invisible_origin(&self, other: &Delimiter) -> bool {
         match (self, other) {
             (Delimiter::Parenthesis, Delimiter::Parenthesis) => true,

compiler/rustc_expand/src/mbe/macro_parser.rs

@@ -77,7 +77,7 @@ use std::rc::Rc;
 
 pub(crate) use NamedMatch::*;
 pub(crate) use ParseResult::*;
-use rustc_ast::token::{self, DocComment, NonterminalKind, Token};
+use rustc_ast::token::{self, DocComment, NonterminalKind, Token, TokenKind};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_errors::ErrorGuaranteed;
 use rustc_lint_defs::pluralize;
@@ -397,7 +397,23 @@ fn token_name_eq(t1: &Token, t2: &Token) -> bool {
     {
         ident1.name == ident2.name && is_raw1 == is_raw2
     } else {
-        t1.kind == t2.kind
+        // Note: we SHOULD NOT use `t1.kind == t2.kind` here, and we should instead compare the
+        // tokens using the special comparison logic below.
+        // It makes sure that variants containing `InvisibleOrigin` will
+        // never compare equal to one another.
+        //
+        // When we had AST-based nonterminals we couldn't compare them, and the
+        // old `Nonterminal` type had an `eq` that always returned false,
+        // resulting in this restriction:
+        // <https://doc.rust-lang.org/nightly/reference/macros-by-example.html#forwarding-a-matched-fragment>
+        // This comparison logic emulates that behaviour. We could consider lifting this
+        // restriction now but there are still cases involving invisible
+        // delimiters that make it harder than it first appears.
+        match (t1.kind, t2.kind) {
+            (TokenKind::OpenInvisible(_) | TokenKind::CloseInvisible(_), _)
+            | (_, TokenKind::OpenInvisible(_) | TokenKind::CloseInvisible(_)) => false,
+            (a, b) => a == b,
+        }
     }
 }