Rollup merge of rust-lang#101573 - lcnr:param-kind-ord, r=BoxyUwU

update `ParamKindOrd`

rust-lang#90207 (comment) 😁

writing comments "for future prs" sure works well :3

r? `@BoxyUwU`

Author: Dylan-DPC

compiler/rustc_ast/src/ast.rs

@@ -33,7 +33,6 @@ use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
 use rustc_span::source_map::{respan, Spanned};
 use rustc_span::symbol::{kw, sym, Ident, Symbol};
 use rustc_span::{Span, DUMMY_SP};
-use std::cmp::Ordering;
 use std::convert::TryFrom;
 use std::fmt;
 use std::mem;
@@ -324,46 +323,17 @@ pub type GenericBounds = Vec<GenericBound>;
 /// Specifies the enforced ordering for generic parameters. In the future,
 /// if we wanted to relax this order, we could override `PartialEq` and
 /// `PartialOrd`, to allow the kinds to be unordered.
-#[derive(Hash, Clone, Copy)]
+#[derive(Hash, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
 pub enum ParamKindOrd {
     Lifetime,
-    Type,
-    Const,
-    // `Infer` is not actually constructed directly from the AST, but is implicitly constructed
-    // during HIR lowering, and `ParamKindOrd` will implicitly order inferred variables last.
-    Infer,
-}
-
-impl Ord for ParamKindOrd {
-    fn cmp(&self, other: &Self) -> Ordering {
-        use ParamKindOrd::*;
-        let to_int = |v| match v {
-            Lifetime => 0,
-            Infer | Type | Const => 1,
-        };
-
-        to_int(*self).cmp(&to_int(*other))
-    }
-}
-impl PartialOrd for ParamKindOrd {
-    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
-        Some(self.cmp(other))
-    }
-}
-impl PartialEq for ParamKindOrd {
-    fn eq(&self, other: &Self) -> bool {
-        self.cmp(other) == Ordering::Equal
-    }
+    TypeOrConst,
 }
-impl Eq for ParamKindOrd {}
 
 impl fmt::Display for ParamKindOrd {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
             ParamKindOrd::Lifetime => "lifetime".fmt(f),
-            ParamKindOrd::Type => "type".fmt(f),
-            ParamKindOrd::Const { .. } => "const".fmt(f),
-            ParamKindOrd::Infer => "infer".fmt(f),
+            ParamKindOrd::TypeOrConst => "type and const".fmt(f),
         }
     }
 }

compiler/rustc_ast_passes/src/ast_validation.rs

@@ -839,10 +839,10 @@ fn validate_generic_param_order(
         let (kind, bounds, span) = (&param.kind, &param.bounds, ident.span);
         let (ord_kind, ident) = match &param.kind {
             GenericParamKind::Lifetime => (ParamKindOrd::Lifetime, ident.to_string()),
-            GenericParamKind::Type { default: _ } => (ParamKindOrd::Type, ident.to_string()),
+            GenericParamKind::Type { default: _ } => (ParamKindOrd::TypeOrConst, ident.to_string()),
             GenericParamKind::Const { ref ty, kw_span: _, default: _ } => {
                 let ty = pprust::ty_to_string(ty);
-                (ParamKindOrd::Const, format!("const {}: {}", ident, ty))
+                (ParamKindOrd::TypeOrConst, format!("const {}: {}", ident, ty))
             }
         };
         param_idents.push((kind, ord_kind, bounds, idx, ident));

compiler/rustc_hir/src/hir.rs

@@ -300,9 +300,9 @@ impl GenericArg<'_> {
     pub fn to_ord(&self) -> ast::ParamKindOrd {
         match self {
             GenericArg::Lifetime(_) => ast::ParamKindOrd::Lifetime,
-            GenericArg::Type(_) => ast::ParamKindOrd::Type,
-            GenericArg::Const(_) => ast::ParamKindOrd::Const,
-            GenericArg::Infer(_) => ast::ParamKindOrd::Infer,
+            GenericArg::Type(_) | GenericArg::Const(_) | GenericArg::Infer(_) => {
+                ast::ParamKindOrd::TypeOrConst
+            }
         }
     }
 

compiler/rustc_middle/src/ty/generics.rs

@@ -27,8 +27,9 @@ impl GenericParamDefKind {
     pub fn to_ord(&self) -> ast::ParamKindOrd {
         match self {
             GenericParamDefKind::Lifetime => ast::ParamKindOrd::Lifetime,
-            GenericParamDefKind::Type { .. } => ast::ParamKindOrd::Type,
-            GenericParamDefKind::Const { .. } => ast::ParamKindOrd::Const,
+            GenericParamDefKind::Type { .. } | GenericParamDefKind::Const { .. } => {
+                ast::ParamKindOrd::TypeOrConst
+            }
         }
     }
 

compiler/rustc_typeck/src/collect/type_of.rs

@@ -65,8 +65,8 @@ pub(super) fn opt_const_param_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Option<
             let ty = item_ctxt.ast_ty_to_ty(hir_ty);
 
             // Iterate through the generics of the projection to find the one that corresponds to
-            // the def_id that this query was called with. We filter to only const args here as a
-            // precaution for if it's ever allowed to elide lifetimes in GAT's. It currently isn't
+            // the def_id that this query was called with. We filter to only type and const args here
+            // as a precaution for if it's ever allowed to elide lifetimes in GAT's. It currently isn't
             // but it can't hurt to be safe ^^
             if let ty::Projection(projection) = ty.kind() {
                 let generics = tcx.generics_of(projection.item_def_id);

src/test/ui/const-generics/argument_order.stderr

@@ -1,4 +1,4 @@
-error: lifetime parameters must be declared prior to const parameters
+error: lifetime parameters must be declared prior to type and const parameters
   --> $DIR/argument_order.rs:6:32
    |
 LL | struct AlsoBad<const N: usize, 'a, T, 'b, const M: usize, U> {
@@ -11,7 +11,7 @@ LL |     let _: AlsoBad<7, 'static, u32, 'static, 17, u16>;
    |                       ^^^^^^^
    |
    = note: lifetime arguments must be provided before type arguments
-   = help: reorder the arguments: lifetimes, then consts: `<'a, 'b, N, T, M, U>`
+   = help: reorder the arguments: lifetimes, then type and consts: `<'a, 'b, N, T, M, U>`
 
 error: aborting due to 2 previous errors
 

src/test/ui/const-generics/const-param-before-other-params.rs

@@ -1,5 +1,5 @@
 fn bar<const X: u8, 'a>(_: &'a ()) {
-    //~^ ERROR lifetime parameters must be declared prior to const parameters
+    //~^ ERROR lifetime parameters must be declared prior to type and const parameters
 }
 
 fn foo<const X: u8, T>(_: &T) {}

src/test/ui/const-generics/const-param-before-other-params.stderr

@@ -1,4 +1,4 @@
-error: lifetime parameters must be declared prior to const parameters
+error: lifetime parameters must be declared prior to type and const parameters
   --> $DIR/const-param-before-other-params.rs:1:21
    |
 LL | fn bar<const X: u8, 'a>(_: &'a ()) {

src/test/ui/const-generics/defaults/intermixed-lifetime.rs

@@ -1,9 +1,9 @@
 // Checks that lifetimes cannot be interspersed between consts and types.
 
 struct Foo<const N: usize, 'a, T = u32>(&'a (), T);
-//~^ Error lifetime parameters must be declared prior to const parameters
+//~^ ERROR lifetime parameters must be declared prior to type and const parameters
 
 struct Bar<const N: usize, T = u32, 'a>(&'a (), T);
-//~^ Error lifetime parameters must be declared prior to type parameters
+//~^ ERROR lifetime parameters must be declared prior to type and const parameters
 
 fn main() {}

src/test/ui/const-generics/defaults/intermixed-lifetime.stderr

@@ -1,10 +1,10 @@
-error: lifetime parameters must be declared prior to const parameters
+error: lifetime parameters must be declared prior to type and const parameters
   --> $DIR/intermixed-lifetime.rs:3:28
    |
 LL | struct Foo<const N: usize, 'a, T = u32>(&'a (), T);
    |           -----------------^^---------- help: reorder the parameters: lifetimes, then consts and types: `<'a, const N: usize, T = u32>`
 
-error: lifetime parameters must be declared prior to type parameters
+error: lifetime parameters must be declared prior to type and const parameters
   --> $DIR/intermixed-lifetime.rs:6:37
    |
 LL | struct Bar<const N: usize, T = u32, 'a>(&'a (), T);