Parser: Recover from attributes applied to types and generic args

compiler/rustc_parse/messages.ftl

@@ -71,6 +71,17 @@ parse_attr_without_generics = attribute without generic parameters
 parse_attribute_on_param_type = attributes cannot be applied to a function parameter's type
     .label = attributes are not allowed here
 
+parse_attribute_on_type = attributes cannot be applied to types
+    .label = attributes are not allowed here
+    .suggestion = remove attribute from here
+
+parse_attribute_on_generic_arg = attributes cannot be applied to generic arguments
+    .label = attributes are not allowed here
+    .suggestion = remove attribute from here
+
+parse_attribute_on_empty_type = attributes cannot be applied here
+    .label = attributes are not allowed here
+
 parse_bad_assoc_type_bounds = bounds on associated types do not belong here
     .label = belongs in `where` clause
 

compiler/rustc_parse/src/errors.rs

@@ -1489,6 +1489,34 @@ pub(crate) struct AttributeOnParamType {
     pub span: Span,
 }
 
+#[derive(Diagnostic)]
+#[diag(parse_attribute_on_type)]
+pub(crate) struct AttributeOnType {
+    #[primary_span]
+    #[label]
+    pub span: Span,
+    #[suggestion(code = "", applicability = "machine-applicable", style = "tool-only")]
+    pub fix_span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(parse_attribute_on_generic_arg)]
+pub(crate) struct AttributeOnGenericArg {
+    #[primary_span]
+    #[label]
+    pub span: Span,
+    #[suggestion(code = "", applicability = "machine-applicable", style = "tool-only")]
+    pub fix_span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(parse_attribute_on_empty_type)]
+pub(crate) struct AttributeOnEmptyType {
+    #[primary_span]
+    #[label]
+    pub span: Span,
+}
+
 #[derive(Diagnostic)]
 #[diag(parse_pattern_method_param_without_body, code = E0642)]
 pub(crate) struct PatternMethodParamWithoutBody {

compiler/rustc_parse/src/parser/path.rs

@@ -17,11 +17,11 @@ use super::ty::{AllowPlus, RecoverQPath, RecoverReturnSign};
 use super::{Parser, Restrictions, TokenType};
 use crate::ast::{PatKind, TyKind};
 use crate::errors::{
-    self, FnPathFoundNamedParams, PathFoundAttributeInParams, PathFoundCVariadicParams,
-    PathSingleColon, PathTripleColon,
+    self, AttributeOnEmptyType, AttributeOnGenericArg, FnPathFoundNamedParams,
+    PathFoundAttributeInParams, PathFoundCVariadicParams, PathSingleColon, PathTripleColon,
 };
 use crate::exp;
-use crate::parser::{CommaRecoveryMode, RecoverColon, RecoverComma};
+use crate::parser::{CommaRecoveryMode, ExprKind, RecoverColon, RecoverComma};
 
 /// Specifies how to parse a path.
 #[derive(Copy, Clone, PartialEq)]
@@ -880,6 +880,12 @@ impl<'a> Parser<'a> {
         &mut self,
         ty_generics: Option<&Generics>,
     ) -> PResult<'a, Option<GenericArg>> {
+        let mut attr_span: Option<Span> = None;
+        if self.token == token::Pound && self.look_ahead(1, |t| *t == token::OpenBracket) {
+            let attrs_wrapper = self.parse_outer_attributes()?;
+            let raw_attrs = attrs_wrapper.take_for_recovery(self.psess);
+            attr_span = Some(raw_attrs[0].span.to(raw_attrs.last().unwrap().span));
+        }
         let start = self.token.span;
         let arg = if self.check_lifetime() && self.look_ahead(1, |t| !t.is_like_plus()) {
             // Parse lifetime argument.
@@ -934,6 +940,9 @@ impl<'a> Parser<'a> {
             }
         } else if self.token.is_keyword(kw::Const) {
             return self.recover_const_param_declaration(ty_generics);
+        } else if let Some(attr_span) = attr_span {
+            let diag = self.dcx().create_err(AttributeOnEmptyType { span: attr_span });
+            return Err(diag);
         } else {
             // Fall back by trying to parse a const-expr expression. If we successfully do so,
             // then we should report an error that it needs to be wrapped in braces.
@@ -953,6 +962,22 @@ impl<'a> Parser<'a> {
                 }
             }
         };
+
+        if let Some(attr_span) = attr_span {
+            let guar = self.dcx().emit_err(AttributeOnGenericArg {
+                span: attr_span,
+                fix_span: attr_span.until(arg.span()),
+            });
+            return Ok(Some(match arg {
+                GenericArg::Type(_) => GenericArg::Type(self.mk_ty(attr_span, TyKind::Err(guar))),
+                GenericArg::Const(_) => {
+                    let error_expr = self.mk_expr(attr_span, ExprKind::Err(guar));
+                    GenericArg::Const(AnonConst { id: ast::DUMMY_NODE_ID, value: error_expr })
+                }
+                GenericArg::Lifetime(lt) => GenericArg::Lifetime(lt),
+            }));
+        }
+
         Ok(Some(arg))
     }
 

compiler/rustc_parse/src/parser/ty.rs

@@ -14,10 +14,10 @@ use thin_vec::{ThinVec, thin_vec};
 
 use super::{Parser, PathStyle, SeqSep, TokenType, Trailing};
 use crate::errors::{
-    self, DynAfterMut, ExpectedFnPathFoundFnKeyword, ExpectedMutOrConstInRawPointerType,
-    FnPtrWithGenerics, FnPtrWithGenericsSugg, HelpUseLatestEdition, InvalidDynKeyword,
-    LifetimeAfterMut, NeedPlusAfterTraitObjectLifetime, NestedCVariadicType,
-    ReturnTypesUseThinArrow,
+    self, AttributeOnEmptyType, AttributeOnType, DynAfterMut, ExpectedFnPathFoundFnKeyword,
+    ExpectedMutOrConstInRawPointerType, FnPtrWithGenerics, FnPtrWithGenericsSugg,
+    HelpUseLatestEdition, InvalidDynKeyword, LifetimeAfterMut, NeedPlusAfterTraitObjectLifetime,
+    NestedCVariadicType, ReturnTypesUseThinArrow,
 };
 use crate::parser::item::FrontMatterParsingMode;
 use crate::{exp, maybe_recover_from_interpolated_ty_qpath};
@@ -253,7 +253,27 @@ impl<'a> Parser<'a> {
     ) -> PResult<'a, P<Ty>> {
         let allow_qpath_recovery = recover_qpath == RecoverQPath::Yes;
         maybe_recover_from_interpolated_ty_qpath!(self, allow_qpath_recovery);
+        if self.token == token::Pound && self.look_ahead(1, |t| *t == token::OpenBracket) {
+            let attrs_wrapper = self.parse_outer_attributes()?;
+            let raw_attrs = attrs_wrapper.take_for_recovery(self.psess);
+            let attr_span = raw_attrs[0].span.to(raw_attrs.last().unwrap().span);
+            let (full_span, guar) = match self.parse_ty() {
+                Ok(ty) => {
+                    let full_span = attr_span.until(ty.span);
+                    let guar = self
+                        .dcx()
+                        .emit_err(AttributeOnType { span: attr_span, fix_span: full_span });
+                    (attr_span, guar)
+                }
+                Err(err) => {
+                    err.cancel();
+                    let guar = self.dcx().emit_err(AttributeOnEmptyType { span: attr_span });
+                    (attr_span, guar)
+                }
+            };
 
+            return Ok(self.mk_ty(full_span, TyKind::Err(guar)));
+        }
         if let Some(ty) = self.eat_metavar_seq_with_matcher(
             |mv_kind| matches!(mv_kind, MetaVarKind::Ty { .. }),
             |this| this.parse_ty_no_question_mark_recover(),

tests/ui/parser/attribute-on-empty.rs

@@ -0,0 +1,29 @@
+//! Regression test for: <https://github.com/rust-lang/rust/issues/144132>
+//!                      <https://github.com/rust-lang/rust/issues/135017>
+
+struct Baz<const N: usize>(i32);
+
+fn main() {
+    let _: Baz<#[cfg(any())]> = todo!();
+    //~^ ERROR attributes cannot be applied here
+}
+
+fn f(_param: #[attr]) {}
+//~^ ERROR attributes cannot be applied to a function parameter's type
+//~| ERROR expected type, found `)`
+
+fn g() -> #[attr] { 0 }
+//~^ ERROR attributes cannot be applied here
+
+struct S {
+    field: #[attr],
+    //~^ ERROR attributes cannot be applied here
+    field1: (#[attr], i32),
+    //~^ ERROR attributes cannot be applied here
+}
+
+type Tuple = (#[attr], String);
+//~^ ERROR attributes cannot be applied here
+
+impl #[attr] {}
+//~^ ERROR attributes cannot be applied here

tests/ui/parser/attribute-on-empty.stderr

@@ -0,0 +1,52 @@
+error: attributes cannot be applied here
+  --> $DIR/attribute-on-empty.rs:7:16
+   |
+LL |     let _: Baz<#[cfg(any())]> = todo!();
+   |          -     ^^^^^^^^^^^^^ attributes are not allowed here
+   |          |
+   |          while parsing the type for `_`
+
+error: attributes cannot be applied to a function parameter's type
+  --> $DIR/attribute-on-empty.rs:11:14
+   |
+LL | fn f(_param: #[attr]) {}
+   |              ^^^^^^^ attributes are not allowed here
+
+error: expected type, found `)`
+  --> $DIR/attribute-on-empty.rs:11:21
+   |
+LL | fn f(_param: #[attr]) {}
+   |                     ^ expected type
+
+error: attributes cannot be applied here
+  --> $DIR/attribute-on-empty.rs:15:11
+   |
+LL | fn g() -> #[attr] { 0 }
+   |           ^^^^^^^ attributes are not allowed here
+
+error: attributes cannot be applied here
+  --> $DIR/attribute-on-empty.rs:19:12
+   |
+LL |     field: #[attr],
+   |            ^^^^^^^ attributes are not allowed here
+
+error: attributes cannot be applied here
+  --> $DIR/attribute-on-empty.rs:21:14
+   |
+LL |     field1: (#[attr], i32),
+   |              ^^^^^^^ attributes are not allowed here
+
+error: attributes cannot be applied here
+  --> $DIR/attribute-on-empty.rs:25:15
+   |
+LL | type Tuple = (#[attr], String);
+   |               ^^^^^^^ attributes are not allowed here
+
+error: attributes cannot be applied here
+  --> $DIR/attribute-on-empty.rs:28:6
+   |
+LL | impl #[attr] {}
+   |      ^^^^^^^ attributes are not allowed here
+
+error: aborting due to 8 previous errors
+

tests/ui/parser/attribute-on-type.fixed

@@ -0,0 +1,58 @@
+//! Regression test for: <https://github.com/rust-lang/rust/issues/144132>
+//!                      <https://github.com/rust-lang/rust/issues/135017>
+
+//@ run-rustfix
+
+#![allow(dead_code, unused_variables)]
+
+struct Foo<T>(T);
+struct Bar<'a>(&'a i32);
+struct Baz<const N: usize>(i32);
+
+fn main() {
+    let foo: Foo<i32> = Foo(2i32);
+    //~^ ERROR attributes cannot be applied to generic arguments
+
+    let _: &'static str = "123";
+    //~^ ERROR attributes cannot be applied to types
+
+    let _: Bar<'static> = Bar(&123);
+    //~^ ERROR attributes cannot be applied to generic arguments
+
+    let _: Baz<42> = Baz(42);
+    //~^ ERROR attributes cannot be applied to generic arguments
+
+    let _: Foo<String> = Foo(String::new());
+    //~^ ERROR attributes cannot be applied to generic arguments
+
+    let _: Bar<'static> = Bar(&456);
+    //~^ ERROR attributes cannot be applied to generic arguments
+
+    let _generic: Box<i32> = Box::new(1);
+    //~^ ERROR attributes cannot be applied to generic arguments
+
+    let _assignment: i32 = *Box::new(1);
+    //~^ ERROR attributes cannot be applied to types
+
+    let _complex: Vec<String> = vec![];
+    //~^ ERROR attributes cannot be applied to generic arguments
+
+    let _nested: Box<Vec<u64>> = Box::new(vec![]);
+    //~^ ERROR attributes cannot be applied to generic arguments
+}
+
+fn g() -> i32 { 0 }
+//~^ ERROR attributes cannot be applied to types
+
+struct S {
+    field: i32,
+    //~^ ERROR attributes cannot be applied to types
+    field1: (i32, i32),
+    //~^ ERROR attributes cannot be applied to types
+}
+
+type Tuple = (i32, String);
+//~^ ERROR attributes cannot be applied to types
+
+impl S {}
+//~^ ERROR attributes cannot be applied to types

tests/ui/parser/attribute-on-type.rs

@@ -0,0 +1,58 @@
+//! Regression test for: <https://github.com/rust-lang/rust/issues/144132>
+//!                      <https://github.com/rust-lang/rust/issues/135017>
+
+//@ run-rustfix
+
+#![allow(dead_code, unused_variables)]
+
+struct Foo<T>(T);
+struct Bar<'a>(&'a i32);
+struct Baz<const N: usize>(i32);
+
+fn main() {
+    let foo: Foo<#[cfg(not(wrong))] i32> = Foo(2i32);
+    //~^ ERROR attributes cannot be applied to generic arguments
+
+    let _: #[attr] &'static str = "123";
+    //~^ ERROR attributes cannot be applied to types
+
+    let _: Bar<#[cfg(any())] 'static> = Bar(&123);
+    //~^ ERROR attributes cannot be applied to generic arguments
+
+    let _: Baz<#[cfg(any())] 42> = Baz(42);
+    //~^ ERROR attributes cannot be applied to generic arguments
+
+    let _: Foo<#[cfg(not(wrong))]String> = Foo(String::new());
+    //~^ ERROR attributes cannot be applied to generic arguments
+
+    let _: Bar<#[cfg(any())]       'static> = Bar(&456);
+    //~^ ERROR attributes cannot be applied to generic arguments
+
+    let _generic: Box<#[attr] i32> = Box::new(1);
+    //~^ ERROR attributes cannot be applied to generic arguments
+
+    let _assignment: #[attr] i32 = *Box::new(1);
+    //~^ ERROR attributes cannot be applied to types
+
+    let _complex: Vec<#[derive(Debug)] String> = vec![];
+    //~^ ERROR attributes cannot be applied to generic arguments
+
+    let _nested: Box<Vec<#[cfg(feature = "test")] u64>> = Box::new(vec![]);
+    //~^ ERROR attributes cannot be applied to generic arguments
+}
+
+fn g() -> #[attr] i32 { 0 }
+//~^ ERROR attributes cannot be applied to types
+
+struct S {
+    field: #[attr] i32,
+    //~^ ERROR attributes cannot be applied to types
+    field1: (#[attr] i32, i32),
+    //~^ ERROR attributes cannot be applied to types
+}
+
+type Tuple = (#[attr] i32, String);
+//~^ ERROR attributes cannot be applied to types
+
+impl #[attr] S {}
+//~^ ERROR attributes cannot be applied to types