Rollup merge of #62417 - alexreg:fix-self-in-type-alias, r=pnkfelix

Fix ICEs when `Self` is used in type aliases

I think it is right just to disallow this at resolution stage rather than let typeck produce a cyclic error. This is in line with previous behaviour. There was probably no need at all for the change that introduced this bug in #57428, so I've simply reversed it.

Fixes #62263, #62364, #62305.

r? @eddyb

src/bootstrap/lib.rs

@@ -197,11 +197,11 @@ pub struct Compiler {
 
 #[derive(PartialEq, Eq, Copy, Clone, Debug)]
 pub enum DocTests {
-    // Default, run normal tests and doc tests.
+    /// Run normal tests and doc tests (default).
     Yes,
-    // Do not run any doc tests.
+    /// Do not run any doc tests.
     No,
-    // Only run doc tests.
+    /// Only run doc tests.
     Only,
 }
 
@@ -221,10 +221,10 @@ pub enum GitRepo {
 /// methods specifically on this structure itself (to make it easier to
 /// organize).
 pub struct Build {
-    // User-specified configuration via config.toml
+    /// User-specified configuration from `config.toml`.
     config: Config,
 
-    // Derived properties from the above two configurations
+    // Properties derived from the above configuration
     src: PathBuf,
     out: PathBuf,
     rust_info: channel::GitInfo,
@@ -240,12 +240,12 @@ pub struct Build {
     doc_tests: DocTests,
     verbosity: usize,
 
-    // Targets for which to build.
+    // Targets for which to build
     build: Interned<String>,
     hosts: Vec<Interned<String>>,
     targets: Vec<Interned<String>>,
 
-    // Stage 0 (downloaded) compiler and cargo or their local rust equivalents.
+    // Stage 0 (downloaded) compiler and cargo or their local rust equivalents
     initial_rustc: PathBuf,
     initial_cargo: PathBuf,
 
@@ -255,7 +255,7 @@ pub struct Build {
     cxx: HashMap<Interned<String>, cc::Tool>,
     ar: HashMap<Interned<String>, PathBuf>,
     ranlib: HashMap<Interned<String>, PathBuf>,
-    // Misc
+    // Miscellaneous
     crates: HashMap<Interned<String>, Crate>,
     is_sudo: bool,
     ci_env: CiEnv,

src/librustc_resolve/lib.rs

@@ -2523,17 +2523,7 @@ impl<'a> Resolver<'a> {
         debug!("(resolving item) resolving {} ({:?})", name, item.node);
 
         match item.node {
-            ItemKind::Ty(_, ref generics) => {
+            ItemKind::Ty(_, ref generics) |
-                self.with_current_self_item(item, |this| {
-                    this.with_generic_param_rib(HasGenericParams(generics, ItemRibKind), |this| {
-                        let item_def_id = this.definitions.local_def_id(item.id);
-                        this.with_self_rib(Res::SelfTy(Some(item_def_id), None), |this| {
-                            visit::walk_item(this, item)
-                        })
-                    })
-                });
-            }
-
             ItemKind::Existential(_, ref generics) |
             ItemKind::Fn(_, _, ref generics, _) => {
                 self.with_generic_param_rib(

src/librustc_typeck/check/mod.rs

@@ -4457,7 +4457,7 @@ pub fn check_bounds_are_used<'tcx>(tcx: TyCtxt<'tcx>, generics: &ty::Generics, t
         return;
     }
 
-    // Make a vector of booleans initially false, set to true when used.
+    // Make a vector of booleans initially `false`; set to `true` when used.
     let mut types_used = vec![false; own_counts.types];
 
     for leaf_ty in ty.walk() {
@@ -4466,7 +4466,7 @@ pub fn check_bounds_are_used<'tcx>(tcx: TyCtxt<'tcx>, generics: &ty::Generics, t
             types_used[index as usize - own_counts.lifetimes] = true;
         } else if let ty::Error = leaf_ty.sty {
             // If there is already another error, do not emit
-            // an error for not using a type Parameter.
+            // an error for not using a type parameter.
             assert!(tcx.sess.has_errors());
             return;
         }

src/test/ui/cast-char.stderr

@@ -1,17 +1,17 @@
 error: only `u8` can be cast into `char`
-  --> $DIR/cast_char.rs:4:23
+  --> $DIR/cast-char.rs:4:23
    |
 LL |     const XYZ: char = 0x1F888 as char;
    |                       ^^^^^^^^^^^^^^^ help: use a `char` literal instead: `'\u{1F888}'`
    |
 note: lint level defined here
-  --> $DIR/cast_char.rs:1:9
+  --> $DIR/cast-char.rs:1:9
    |
 LL | #![deny(overflowing_literals)]
    |         ^^^^^^^^^^^^^^^^^^^^
 
 error: only `u8` can be cast into `char`
-  --> $DIR/cast_char.rs:6:22
+  --> $DIR/cast-char.rs:6:22
    |
 LL |     const XY: char = 129160 as char;
    |                      ^^^^^^^^^^^^^^ help: use a `char` literal instead: `'\u{1F888}'`

src/test/ui/type-alias/issue-62263-self-in-atb.rs

@@ -0,0 +1,8 @@
+pub trait Trait {
+    type A;
+}
+
+pub type Alias = dyn Trait<A = Self::A>;
+//~^ ERROR failed to resolve: use of undeclared type or module `Self` [E0433]
+
+fn main() {}

src/test/ui/type-alias/issue-62263-self-in-atb.stderr

@@ -0,0 +1,9 @@
+error[E0433]: failed to resolve: use of undeclared type or module `Self`
+  --> $DIR/issue-62263-self-in-atb.rs:5:32
+   |
+LL | pub type Alias = dyn Trait<A = Self::A>;
+   |                                ^^^^ use of undeclared type or module `Self`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0433`.

src/test/ui/type-alias/issue-62305-self-assoc-ty.rs

@@ -0,0 +1,4 @@
+type Alias = Self::Target;
+//~^ ERROR failed to resolve: use of undeclared type or module `Self` [E0433]
+
+fn main() {}

src/test/ui/type-alias/issue-62305-self-assoc-ty.stderr

@@ -0,0 +1,9 @@
+error[E0433]: failed to resolve: use of undeclared type or module `Self`
+  --> $DIR/issue-62305-self-assoc-ty.rs:1:14
+   |
+LL | type Alias = Self::Target;
+   |              ^^^^ use of undeclared type or module `Self`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0433`.

src/test/ui/type-alias/issue-62364-self-ty-arg.rs

@@ -0,0 +1,8 @@
+struct Struct<P1> {
+    field: P1,
+}
+
+type Alias<'a> = Struct<&'a Self>;
+//~^ ERROR cannot find type `Self` in this scope [E0411]
+
+fn main() {}

src/test/ui/type-alias/issue-62364-self-ty-arg.stderr

@@ -0,0 +1,9 @@
+error[E0411]: cannot find type `Self` in this scope
+  --> $DIR/issue-62364-self-ty-arg.rs:5:29
+   |
+LL | type Alias<'a> = Struct<&'a Self>;
+   |                             ^^^^ `Self` is only available in impls, traits, and type definitions
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0411`.