Add correct suggestion for multi-references for self type in method

compiler/rustc_ast/src/ast.rs

@@ -715,6 +715,15 @@ impl Pat {
         }
     }
 
+    /// Strip off all reference patterns (`&`, `&mut`) and return the inner pattern.
+    pub fn peel_refs(&self) -> &Pat {
+        let mut current = self;
+        while let PatKind::Ref(inner, _) = &current.kind {
+            current = inner;
+        }
+        current
+    }
+
     /// Is this a `..` pattern?
     pub fn is_rest(&self) -> bool {
         matches!(self.kind, PatKind::Rest)

compiler/rustc_parse/src/parser/diagnostics.rs

@@ -2,13 +2,12 @@ use std::mem::take;
 use std::ops::{Deref, DerefMut};
 
 use ast::token::IdentIsRaw;
-use rustc_ast as ast;
 use rustc_ast::token::{self, Lit, LitKind, Token, TokenKind};
 use rustc_ast::util::parser::AssocOp;
 use rustc_ast::{
-    AngleBracketedArg, AngleBracketedArgs, AnonConst, AttrVec, BinOpKind, BindingMode, Block,
-    BlockCheckMode, Expr, ExprKind, GenericArg, Generics, Item, ItemKind, Param, Pat, PatKind,
-    Path, PathSegment, QSelf, Recovered, Ty, TyKind,
+    self as ast, AngleBracketedArg, AngleBracketedArgs, AnonConst, AttrVec, BinOpKind, BindingMode,
+    Block, BlockCheckMode, Expr, ExprKind, GenericArg, Generics, Item, ItemKind, Param, Pat,
+    PatKind, Path, PathSegment, QSelf, Recovered, Ty, TyKind,
 };
 use rustc_ast_pretty::pprust;
 use rustc_data_structures::fx::FxHashSet;
@@ -2290,6 +2289,38 @@ impl<'a> Parser<'a> {
                         pat.span.shrink_to_hi(),
                         pat.span.shrink_to_lo(),
                     ),
+                    PatKind::Ref(ref inner_pat, _)
+                    // Fix suggestions for multi-reference `self` parameters (e.g. `&&&self`)
+                    // cc: https://github.com/rust-lang/rust/pull/146305
+                        if let PatKind::Ref(_, _) = &inner_pat.kind
+                            && let PatKind::Path(_, path) = &pat.peel_refs().kind
+                            && let [a, ..] = path.segments.as_slice()
+                            && a.ident.name == kw::SelfLower =>
+                    {
+                        let mut inner = inner_pat;
+                        let mut span_vec = vec![pat.span];
+
+                        while let PatKind::Ref(ref inner_type, _) = inner.kind {
+                            inner = inner_type;
+                            span_vec.push(inner.span.shrink_to_lo());
+                        }
+
+                        let span = match span_vec.len() {
+                            // Should be unreachable: match guard ensures at least 2 references
+                            0 | 1 => unreachable!(),
+                            2 => span_vec[0].until(inner_pat.span.shrink_to_lo()),
+                            _ => span_vec[0].until(span_vec[span_vec.len() - 2].shrink_to_lo()),
+                        };
+
+                        err.span_suggestion_verbose(
+                            span,
+                            "`self` should be `self`, `&self` or `&mut self`, consider removing extra references",
+                            "".to_string(),
+                            Applicability::MachineApplicable,
+                        );
+
+                        return None;
+                    }
                     // Also catches `fn foo(&a)`.
                     PatKind::Ref(ref inner_pat, mutab)
                         if let PatKind::Ident(_, ident, _) = inner_pat.clone().kind =>

tests/ui/self/lot-of-references-self.rs

@@ -0,0 +1,28 @@
+struct A ;
+
+impl A {
+    fn a(&&self) {}
+    //~^ ERROR expected one of
+    //~| HELP `self` should be `self`, `&self` or `&mut self`, consider removing extra references
+    fn b(&&&&&&self) {}
+    //~^ ERROR expected one of
+    //~| HELP `self` should be `self`, `&self` or `&mut self`, consider removing extra references
+    fn c(&self) {}
+    fn d(&mut &self) {}
+    //~^ ERROR expected one of
+    //~| HELP `self` should be `self`, `&self` or `&mut self`, consider removing extra references
+    fn e(&mut &&&self) {}
+    //~^ ERROR expected one of
+    //~| HELP `self` should be `self`, `&self` or `&mut self`, consider removing extra references
+    fn f(&mut &mut &mut self) {}
+    //~^ ERROR expected one of
+    //~| HELP `self` should be `self`, `&self` or `&mut self`, consider removing extra references
+    fn g(&mut & &mut self) {}
+    //~^ ERROR expected one of
+    //~| HELP `self` should be `self`, `&self` or `&mut self`, consider removing extra references
+    fn h(&mut & & & && &        & self) {}
+    //~^ ERROR expected one of
+    //~| HELP `self` should be `self`, `&self` or `&mut self`, consider removing extra references
+}
+
+fn main() {}

tests/ui/self/lot-of-references-self.stderr

@@ -0,0 +1,86 @@
+error: expected one of `!`, `(`, `...`, `..=`, `..`, `::`, `:`, `{`, or `|`, found `)`
+  --> $DIR/lot-of-references-self.rs:4:16
+   |
+LL |     fn a(&&self) {}
+   |                ^ expected one of 9 possible tokens
+   |
+help: `self` should be `self`, `&self` or `&mut self`, consider removing extra references
+   |
+LL -     fn a(&&self) {}
+LL +     fn a(&self) {}
+   |
+
+error: expected one of `!`, `(`, `...`, `..=`, `..`, `::`, `:`, `{`, or `|`, found `)`
+  --> $DIR/lot-of-references-self.rs:7:20
+   |
+LL |     fn b(&&&&&&self) {}
+   |                    ^ expected one of 9 possible tokens
+   |
+help: `self` should be `self`, `&self` or `&mut self`, consider removing extra references
+   |
+LL -     fn b(&&&&&&self) {}
+LL +     fn b(&self) {}
+   |
+
+error: expected one of `!`, `(`, `...`, `..=`, `..`, `::`, `:`, `{`, or `|`, found `)`
+  --> $DIR/lot-of-references-self.rs:11:20
+   |
+LL |     fn d(&mut &self) {}
+   |                    ^ expected one of 9 possible tokens
+   |
+help: `self` should be `self`, `&self` or `&mut self`, consider removing extra references
+   |
+LL -     fn d(&mut &self) {}
+LL +     fn d(&self) {}
+   |
+
+error: expected one of `!`, `(`, `...`, `..=`, `..`, `::`, `:`, `{`, or `|`, found `)`
+  --> $DIR/lot-of-references-self.rs:14:22
+   |
+LL |     fn e(&mut &&&self) {}
+   |                      ^ expected one of 9 possible tokens
+   |
+help: `self` should be `self`, `&self` or `&mut self`, consider removing extra references
+   |
+LL -     fn e(&mut &&&self) {}
+LL +     fn e(&self) {}
+   |
+
+error: expected one of `!`, `(`, `...`, `..=`, `..`, `::`, `:`, `{`, or `|`, found `)`
+  --> $DIR/lot-of-references-self.rs:17:29
+   |
+LL |     fn f(&mut &mut &mut self) {}
+   |                             ^ expected one of 9 possible tokens
+   |
+help: `self` should be `self`, `&self` or `&mut self`, consider removing extra references
+   |
+LL -     fn f(&mut &mut &mut self) {}
+LL +     fn f(&mut self) {}
+   |
+
+error: expected one of `!`, `(`, `...`, `..=`, `..`, `::`, `:`, `{`, or `|`, found `)`
+  --> $DIR/lot-of-references-self.rs:20:26
+   |
+LL |     fn g(&mut & &mut self) {}
+   |                          ^ expected one of 9 possible tokens
+   |
+help: `self` should be `self`, `&self` or `&mut self`, consider removing extra references
+   |
+LL -     fn g(&mut & &mut self) {}
+LL +     fn g(&mut self) {}
+   |
+
+error: expected one of `!`, `(`, `...`, `..=`, `..`, `::`, `:`, `{`, or `|`, found `)`
+  --> $DIR/lot-of-references-self.rs:23:39
+   |
+LL |     fn h(&mut & & & && &        & self) {}
+   |                                       ^ expected one of 9 possible tokens
+   |
+help: `self` should be `self`, `&self` or `&mut self`, consider removing extra references
+   |
+LL -     fn h(&mut & & & && &        & self) {}
+LL +     fn h(& self) {}
+   |
+
+error: aborting due to 7 previous errors
+