smarter E0390

compiler/rustc_error_codes/src/error_codes/E0390.md

@@ -1,4 +1,4 @@
-A method was implemented on a primitive type.
+A method or constant was implemented on a primitive type.
 
 Erroneous code example:
 
@@ -12,7 +12,8 @@ impl *mut Foo {}
 //        `#[lang = "mut_ptr"]` is allowed for the `*mut T` primitive
 ```
 
-This isn't allowed, but using a trait to implement a method is a good solution.
+This isn't allowed, but using a trait to implement a method or constant
+is a good solution.
 Example:
 
 ```

compiler/rustc_typeck/src/coherence/inherent_impls.rs

@@ -44,8 +44,8 @@ struct InherentCollect<'tcx> {
 
 impl ItemLikeVisitor<'v> for InherentCollect<'tcx> {
     fn visit_item(&mut self, item: &hir::Item<'_>) {
-        let ty = match item.kind {
+        let (ty, assoc_items) = match item.kind {
-            hir::ItemKind::Impl { of_trait: None, ref self_ty, .. } => self_ty,
+            hir::ItemKind::Impl { of_trait: None, ref self_ty, items, .. } => (self_ty, items),
             _ => return,
         };
 
@@ -70,6 +70,7 @@ impl ItemLikeVisitor<'v> for InherentCollect<'tcx> {
                     "bool",
                     "bool",
                     item.span,
+                    assoc_items,
                 );
             }
             ty::Char => {
@@ -80,6 +81,7 @@ impl ItemLikeVisitor<'v> for InherentCollect<'tcx> {
                     "char",
                     "char",
                     item.span,
+                    assoc_items,
                 );
             }
             ty::Str => {
@@ -90,6 +92,7 @@ impl ItemLikeVisitor<'v> for InherentCollect<'tcx> {
                     "str",
                     "str",
                     item.span,
+                    assoc_items,
                 );
             }
             ty::Slice(slice_item) if slice_item == self.tcx.types.u8 => {
@@ -100,6 +103,7 @@ impl ItemLikeVisitor<'v> for InherentCollect<'tcx> {
                     "slice_u8",
                     "[u8]",
                     item.span,
+                    assoc_items,
                 );
             }
             ty::Slice(_) => {
@@ -110,6 +114,7 @@ impl ItemLikeVisitor<'v> for InherentCollect<'tcx> {
                     "slice",
                     "[T]",
                     item.span,
+                    assoc_items,
                 );
             }
             ty::Array(_, _) => {
@@ -120,6 +125,7 @@ impl ItemLikeVisitor<'v> for InherentCollect<'tcx> {
                     "array",
                     "[T; N]",
                     item.span,
+                    assoc_items,
                 );
             }
             ty::RawPtr(ty::TypeAndMut { ty: inner, mutbl: hir::Mutability::Not })
@@ -132,6 +138,7 @@ impl ItemLikeVisitor<'v> for InherentCollect<'tcx> {
                     "const_slice_ptr",
                     "*const [T]",
                     item.span,
+                    assoc_items,
                 );
             }
             ty::RawPtr(ty::TypeAndMut { ty: inner, mutbl: hir::Mutability::Mut })
@@ -144,6 +151,7 @@ impl ItemLikeVisitor<'v> for InherentCollect<'tcx> {
                     "mut_slice_ptr",
                     "*mut [T]",
                     item.span,
+                    assoc_items,
                 );
             }
             ty::RawPtr(ty::TypeAndMut { ty: _, mutbl: hir::Mutability::Not }) => {
@@ -154,6 +162,7 @@ impl ItemLikeVisitor<'v> for InherentCollect<'tcx> {
                     "const_ptr",
                     "*const T",
                     item.span,
+                    assoc_items,
                 );
             }
             ty::RawPtr(ty::TypeAndMut { ty: _, mutbl: hir::Mutability::Mut }) => {
@@ -164,6 +173,7 @@ impl ItemLikeVisitor<'v> for InherentCollect<'tcx> {
                     "mut_ptr",
                     "*mut T",
                     item.span,
+                    assoc_items,
                 );
             }
             ty::Int(ast::IntTy::I8) => {
@@ -174,6 +184,7 @@ impl ItemLikeVisitor<'v> for InherentCollect<'tcx> {
                     "i8",
                     "i8",
                     item.span,
+                    assoc_items,
                 );
             }
             ty::Int(ast::IntTy::I16) => {
@@ -184,6 +195,7 @@ impl ItemLikeVisitor<'v> for InherentCollect<'tcx> {
                     "i16",
                     "i16",
                     item.span,
+                    assoc_items,
                 );
             }
             ty::Int(ast::IntTy::I32) => {
@@ -194,6 +206,7 @@ impl ItemLikeVisitor<'v> for InherentCollect<'tcx> {
                     "i32",
                     "i32",
                     item.span,
+                    assoc_items,
                 );
             }
             ty::Int(ast::IntTy::I64) => {
@@ -204,6 +217,7 @@ impl ItemLikeVisitor<'v> for InherentCollect<'tcx> {
                     "i64",
                     "i64",
                     item.span,
+                    assoc_items,
                 );
             }
             ty::Int(ast::IntTy::I128) => {
@@ -214,6 +228,7 @@ impl ItemLikeVisitor<'v> for InherentCollect<'tcx> {
                     "i128",
                     "i128",
                     item.span,
+                    assoc_items,
                 );
             }
             ty::Int(ast::IntTy::Isize) => {
@@ -224,6 +239,7 @@ impl ItemLikeVisitor<'v> for InherentCollect<'tcx> {
                     "isize",
                     "isize",
                     item.span,
+                    assoc_items,
                 );
             }
             ty::Uint(ast::UintTy::U8) => {
@@ -234,6 +250,7 @@ impl ItemLikeVisitor<'v> for InherentCollect<'tcx> {
                     "u8",
                     "u8",
                     item.span,
+                    assoc_items,
                 );
             }
             ty::Uint(ast::UintTy::U16) => {
@@ -244,6 +261,7 @@ impl ItemLikeVisitor<'v> for InherentCollect<'tcx> {
                     "u16",
                     "u16",
                     item.span,
+                    assoc_items,
                 );
             }
             ty::Uint(ast::UintTy::U32) => {
@@ -254,6 +272,7 @@ impl ItemLikeVisitor<'v> for InherentCollect<'tcx> {
                     "u32",
                     "u32",
                     item.span,
+                    assoc_items,
                 );
             }
             ty::Uint(ast::UintTy::U64) => {
@@ -264,6 +283,7 @@ impl ItemLikeVisitor<'v> for InherentCollect<'tcx> {
                     "u64",
                     "u64",
                     item.span,
+                    assoc_items,
                 );
             }
             ty::Uint(ast::UintTy::U128) => {
@@ -274,6 +294,7 @@ impl ItemLikeVisitor<'v> for InherentCollect<'tcx> {
                     "u128",
                     "u128",
                     item.span,
+                    assoc_items,
                 );
             }
             ty::Uint(ast::UintTy::Usize) => {
@@ -284,6 +305,7 @@ impl ItemLikeVisitor<'v> for InherentCollect<'tcx> {
                     "usize",
                     "usize",
                     item.span,
+                    assoc_items,
                 );
             }
             ty::Float(ast::FloatTy::F32) => {
@@ -294,6 +316,7 @@ impl ItemLikeVisitor<'v> for InherentCollect<'tcx> {
                     "f32",
                     "f32",
                     item.span,
+                    assoc_items,
                 );
             }
             ty::Float(ast::FloatTy::F64) => {
@@ -304,6 +327,7 @@ impl ItemLikeVisitor<'v> for InherentCollect<'tcx> {
                     "f64",
                     "f64",
                     item.span,
+                    assoc_items,
                 );
             }
             ty::Error(_) => {}
@@ -369,6 +393,7 @@ impl InherentCollect<'tcx> {
         lang: &str,
         ty: &str,
         span: Span,
+        assoc_items: &[hir::ImplItemRef<'_>],
     ) {
         match (lang_def_id, lang_def_id2) {
             (Some(lang_def_id), _) if lang_def_id == impl_def_id.to_def_id() => {
@@ -387,7 +412,34 @@ impl InherentCollect<'tcx> {
                     lang,
                     ty
                 )
-                .span_help(span, "consider using a trait to implement these methods")
+                .span_help(
+                    span,
+                    &format!("consider using a trait{}", {
+                        if assoc_items.len() == 0 {
+                            String::new()
+                        } else {
+                            let plural = assoc_items.len() > 1;
+                            format!(
+                                " to implement {} {}{}",
+                                if plural { "these" } else { "this" },
+                                {
+                                    let item_types = assoc_items.iter().map(|x| x.kind);
+                                    if item_types.clone().all(|x| x == hir::AssocItemKind::Const) {
+                                        "constant"
+                                    } else if item_types
+                                        .clone()
+                                        .all(|x| matches! {x, hir::AssocItemKind::Fn{ .. } })
+                                    {
+                                        "method"
+                                    } else {
+                                        "associated item"
+                                    }
+                                },
+                                if plural { "s" } else { "" }
+                            )
+                        }
+                    }),
+                )
                 .emit();
             }
         }

src/test/ui/error-codes/E0390.stderr

@@ -4,7 +4,7 @@ error[E0390]: only a single inherent implementation marked with `#[lang = "mut_p
 LL | impl *mut Foo {}
    | ^^^^^^^^^^^^^^^^
    |
-help: consider using a trait to implement these methods
+help: consider using a trait
   --> $DIR/E0390.rs:5:1
    |
 LL | impl *mut Foo {}

src/test/ui/kinds-of-primitive-impl.rs

@@ -0,0 +1,23 @@
+// ignore-tidy-linelength
+
+
+impl u8 {
+//~^ error: only a single inherent implementation marked with `#[lang = "u8"]` is allowed for the `u8` primitive
+    pub const B: u8 = 0;
+}
+
+impl str {
+//~^ error: only a single inherent implementation marked with `#[lang = "str"]` is allowed for the `str` primitive
+    fn foo() {}
+    fn bar(self) {}
+}
+
+impl char {
+//~^ error: only a single inherent implementation marked with `#[lang = "char"]` is allowed for the `char` primitive
+    pub const B: u8 = 0;
+    pub const C: u8 = 0;
+    fn foo() {}
+    fn bar(self) {}
+}
+
+fn main() {}

src/test/ui/kinds-of-primitive-impl.stderr

@@ -0,0 +1,65 @@
+error[E0390]: only a single inherent implementation marked with `#[lang = "u8"]` is allowed for the `u8` primitive
+  --> $DIR/kinds-of-primitive-impl.rs:4:1
+   |
+LL | / impl u8 {
+LL | |
+LL | |     pub const B: u8 = 0;
+LL | | }
+   | |_^
+   |
+help: consider using a trait to implement this constant
+  --> $DIR/kinds-of-primitive-impl.rs:4:1
+   |
+LL | / impl u8 {
+LL | |
+LL | |     pub const B: u8 = 0;
+LL | | }
+   | |_^
+
+error[E0390]: only a single inherent implementation marked with `#[lang = "str"]` is allowed for the `str` primitive
+  --> $DIR/kinds-of-primitive-impl.rs:9:1
+   |
+LL | / impl str {
+LL | |
+LL | |     fn foo() {}
+LL | |     fn bar(self) {}
+LL | | }
+   | |_^
+   |
+help: consider using a trait to implement these methods
+  --> $DIR/kinds-of-primitive-impl.rs:9:1
+   |
+LL | / impl str {
+LL | |
+LL | |     fn foo() {}
+LL | |     fn bar(self) {}
+LL | | }
+   | |_^
+
+error[E0390]: only a single inherent implementation marked with `#[lang = "char"]` is allowed for the `char` primitive
+  --> $DIR/kinds-of-primitive-impl.rs:15:1
+   |
+LL | / impl char {
+LL | |
+LL | |     pub const B: u8 = 0;
+LL | |     pub const C: u8 = 0;
+LL | |     fn foo() {}
+LL | |     fn bar(self) {}
+LL | | }
+   | |_^
+   |
+help: consider using a trait to implement these associated items
+  --> $DIR/kinds-of-primitive-impl.rs:15:1
+   |
+LL | / impl char {
+LL | |
+LL | |     pub const B: u8 = 0;
+LL | |     pub const C: u8 = 0;
+LL | |     fn foo() {}
+LL | |     fn bar(self) {}
+LL | | }
+   | |_^
+
+error: aborting due to 3 previous errors
+
+For more information about this error, try `rustc --explain E0390`.

src/test/ui/single-primitive-inherent-impl.stderr

@@ -6,7 +6,7 @@ LL | |
 LL | | }
    | |_^
    |
-help: consider using a trait to implement these methods
+help: consider using a trait
   --> $DIR/single-primitive-inherent-impl.rs:11:1
    |
 LL | / impl str {