Only mention const generics if enabled.

This commit updates the generic parameter re-ordering diagnostic to only
mention const generics if the feature is enabled.

src/librustc_passes/ast_validation.rs

@@ -360,6 +360,7 @@ enum GenericPosition {
 }
 
 fn validate_generics_order<'a>(
+    sess: &Session,
     handler: &errors::Handler,
     generics: impl Iterator<
         Item = (
@@ -426,7 +427,11 @@ fn validate_generics_order<'a>(
         if let GenericPosition::Param = pos {
             err.span_suggestion(
                 span,
-                &format!("reorder the {}s: lifetimes, then types, then consts", pos_str),
+                &format!(
+                    "reorder the {}s: lifetimes, then types{}",
+                    pos_str,
+                    if sess.features_untracked().const_generics { ", then consts" } else { "" },
+                ),
                 ordered_params.clone(),
                 Applicability::MachineApplicable,
             );
@@ -709,13 +714,19 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
         match *generic_args {
             GenericArgs::AngleBracketed(ref data) => {
                 walk_list!(self, visit_generic_arg, &data.args);
-                validate_generics_order(self.err_handler(), data.args.iter().map(|arg| {
-                    (match arg {
-                        GenericArg::Lifetime(..) => ParamKindOrd::Lifetime,
-                        GenericArg::Type(..) => ParamKindOrd::Type,
-                        GenericArg::Const(..) => ParamKindOrd::Const,
-                    }, None, arg.span(), None)
-                }), GenericPosition::Arg, generic_args.span());
+                validate_generics_order(
+                    self.session,
+                    self.err_handler(),
+                    data.args.iter().map(|arg| {
+                        (match arg {
+                            GenericArg::Lifetime(..) => ParamKindOrd::Lifetime,
+                            GenericArg::Type(..) => ParamKindOrd::Type,
+                            GenericArg::Const(..) => ParamKindOrd::Const,
+                        }, None, arg.span(), None)
+                    }),
+                    GenericPosition::Arg,
+                    generic_args.span(),
+                );
 
                 // Type bindings such as `Item=impl Debug` in `Iterator<Item=Debug>`
                 // are allowed to contain nested `impl Trait`.
@@ -748,18 +759,24 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
             }
         }
 
-        validate_generics_order(self.err_handler(), generics.params.iter().map(|param| {
-            let ident = Some(param.ident.to_string());
-            let (kind, ident) = match &param.kind {
-                GenericParamKind::Lifetime { .. } => (ParamKindOrd::Lifetime, ident),
-                GenericParamKind::Type { .. } => (ParamKindOrd::Type, ident),
-                GenericParamKind::Const { ref ty } => {
-                    let ty = pprust::ty_to_string(ty);
-                    (ParamKindOrd::Const, Some(format!("const {}: {}", param.ident, ty)))
-                }
-            };
-            (kind, Some(&*param.bounds), param.ident.span, ident)
-        }), GenericPosition::Param, generics.span);
+        validate_generics_order(
+            self.session,
+            self.err_handler(),
+            generics.params.iter().map(|param| {
+                let ident = Some(param.ident.to_string());
+                let (kind, ident) = match &param.kind {
+                    GenericParamKind::Lifetime { .. } => (ParamKindOrd::Lifetime, ident),
+                    GenericParamKind::Type { .. } => (ParamKindOrd::Type, ident),
+                    GenericParamKind::Const { ref ty } => {
+                        let ty = pprust::ty_to_string(ty);
+                        (ParamKindOrd::Const, Some(format!("const {}: {}", param.ident, ty)))
+                    }
+                };
+                (kind, Some(&*param.bounds), param.ident.span, ident)
+            }),
+            GenericPosition::Param,
+            generics.span,
+        );
 
         for predicate in &generics.where_clause.predicates {
             if let WherePredicate::EqPredicate(ref predicate) = *predicate {

src/test/ui/issue-59508-1.rs

@@ -0,0 +1,18 @@
+#![allow(dead_code)]
+#![feature(const_generics)]
+//~^ WARN the feature `const_generics` is incomplete and may cause the compiler to crash
+
+// This test checks that generic parameter re-ordering diagnostic suggestions mention that
+// consts come after types and lifetimes when the `const_generics` feature is enabled.
+// We cannot run rustfix on this test because of the above const generics warning.
+
+struct A;
+
+impl A {
+    pub fn do_things<T, 'a, 'b: 'a>() {
+    //~^ ERROR lifetime parameters must be declared prior to type parameters
+        println!("panic");
+    }
+}
+
+fn main() {}

src/test/ui/issue-59508-1.stderr

@@ -0,0 +1,14 @@
+warning: the feature `const_generics` is incomplete and may cause the compiler to crash
+  --> $DIR/issue-59508-1.rs:2:12
+   |
+LL | #![feature(const_generics)]
+   |            ^^^^^^^^^^^^^^
+
+error: lifetime parameters must be declared prior to type parameters
+  --> $DIR/issue-59508-1.rs:12:25
+   |
+LL |     pub fn do_things<T, 'a, 'b: 'a>() {
+   |                     ----^^--^^----- help: reorder the parameters: lifetimes, then types, then consts: `<'a, 'b: 'a, T>`
+
+error: aborting due to previous error
+

src/test/ui/issue-59508.stderr

@@ -2,7 +2,7 @@ error: lifetime parameters must be declared prior to type parameters
   --> $DIR/issue-59508.rs:10:25
    |
 LL |     pub fn do_things<T, 'a, 'b: 'a>() {
-   |                     ----^^--^^----- help: reorder the parameters: lifetimes, then types, then consts: `<'a, 'b: 'a, T>`
+   |                     ----^^--^^----- help: reorder the parameters: lifetimes, then types: `<'a, 'b: 'a, T>`
 
 error: aborting due to previous error
 

src/test/ui/lifetime-before-type-params.stderr

@@ -2,25 +2,25 @@ error: lifetime parameters must be declared prior to type parameters
   --> $DIR/lifetime-before-type-params.rs:2:13
    |
 LL | fn first<T, 'a, 'b>() {}
-   |         ----^^--^^- help: reorder the parameters: lifetimes, then types, then consts: `<'a, 'b, T>`
+   |         ----^^--^^- help: reorder the parameters: lifetimes, then types: `<'a, 'b, T>`
 
 error: lifetime parameters must be declared prior to type parameters
   --> $DIR/lifetime-before-type-params.rs:4:18
    |
 LL | fn second<'a, T, 'b>() {}
-   |          --------^^- help: reorder the parameters: lifetimes, then types, then consts: `<'a, 'b, T>`
+   |          --------^^- help: reorder the parameters: lifetimes, then types: `<'a, 'b, T>`
 
 error: lifetime parameters must be declared prior to type parameters
   --> $DIR/lifetime-before-type-params.rs:6:16
    |
 LL | fn third<T, U, 'a>() {}
-   |         -------^^- help: reorder the parameters: lifetimes, then types, then consts: `<'a, T, U>`
+   |         -------^^- help: reorder the parameters: lifetimes, then types: `<'a, T, U>`
 
 error: lifetime parameters must be declared prior to type parameters
   --> $DIR/lifetime-before-type-params.rs:8:18
    |
 LL | fn fourth<'a, T, 'b, U, 'c, V>() {}
-   |          --------^^-----^^---- help: reorder the parameters: lifetimes, then types, then consts: `<'a, 'b, 'c, T, U, V>`
+   |          --------^^-----^^---- help: reorder the parameters: lifetimes, then types: `<'a, 'b, 'c, T, U, V>`
 
 error[E0601]: `main` function not found in crate `lifetime_before_type_params`
    |

src/test/ui/parser/issue-14303-enum.stderr

@@ -2,7 +2,7 @@ error: lifetime parameters must be declared prior to type parameters
   --> $DIR/issue-14303-enum.rs:1:15
    |
 LL | enum X<'a, T, 'b> {
-   |       --------^^- help: reorder the parameters: lifetimes, then types, then consts: `<'a, 'b, T>`
+   |       --------^^- help: reorder the parameters: lifetimes, then types: `<'a, 'b, T>`
 
 error: aborting due to previous error
 

src/test/ui/parser/issue-14303-fn-def.stderr

@@ -2,7 +2,7 @@ error: lifetime parameters must be declared prior to type parameters
   --> $DIR/issue-14303-fn-def.rs:1:15
    |
 LL | fn foo<'a, T, 'b>(x: &'a T) {}
-   |       --------^^- help: reorder the parameters: lifetimes, then types, then consts: `<'a, 'b, T>`
+   |       --------^^- help: reorder the parameters: lifetimes, then types: `<'a, 'b, T>`
 
 error: aborting due to previous error
 

src/test/ui/parser/issue-14303-impl.stderr

@@ -2,7 +2,7 @@ error: lifetime parameters must be declared prior to type parameters
   --> $DIR/issue-14303-impl.rs:3:13
    |
 LL | impl<'a, T, 'b> X<T> {}
-   |     --------^^- help: reorder the parameters: lifetimes, then types, then consts: `<'a, 'b, T>`
+   |     --------^^- help: reorder the parameters: lifetimes, then types: `<'a, 'b, T>`
 
 error: aborting due to previous error
 

src/test/ui/parser/issue-14303-struct.stderr

@@ -2,7 +2,7 @@ error: lifetime parameters must be declared prior to type parameters
   --> $DIR/issue-14303-struct.rs:1:17
    |
 LL | struct X<'a, T, 'b> {
-   |         --------^^- help: reorder the parameters: lifetimes, then types, then consts: `<'a, 'b, T>`
+   |         --------^^- help: reorder the parameters: lifetimes, then types: `<'a, 'b, T>`
 
 error: aborting due to previous error
 

src/test/ui/parser/issue-14303-trait.stderr

@@ -2,7 +2,7 @@ error: lifetime parameters must be declared prior to type parameters
   --> $DIR/issue-14303-trait.rs:1:18
    |
 LL | trait Foo<'a, T, 'b> {}
-   |          --------^^- help: reorder the parameters: lifetimes, then types, then consts: `<'a, 'b, T>`
+   |          --------^^- help: reorder the parameters: lifetimes, then types: `<'a, 'b, T>`
 
 error: aborting due to previous error
 

src/test/ui/suggestions/suggest-move-lifetimes.stderr

@@ -2,25 +2,25 @@ error: lifetime parameters must be declared prior to type parameters
   --> $DIR/suggest-move-lifetimes.rs:1:13
    |
 LL | struct A<T, 'a> {
-   |         ----^^- help: reorder the parameters: lifetimes, then types, then consts: `<'a, T>`
+   |         ----^^- help: reorder the parameters: lifetimes, then types: `<'a, T>`
 
 error: lifetime parameters must be declared prior to type parameters
   --> $DIR/suggest-move-lifetimes.rs:5:13
    |
 LL | struct B<T, 'a, U> {
-   |         ----^^---- help: reorder the parameters: lifetimes, then types, then consts: `<'a, T, U>`
+   |         ----^^---- help: reorder the parameters: lifetimes, then types: `<'a, T, U>`
 
 error: lifetime parameters must be declared prior to type parameters
   --> $DIR/suggest-move-lifetimes.rs:10:16
    |
 LL | struct C<T, U, 'a> {
-   |         -------^^- help: reorder the parameters: lifetimes, then types, then consts: `<'a, T, U>`
+   |         -------^^- help: reorder the parameters: lifetimes, then types: `<'a, T, U>`
 
 error: lifetime parameters must be declared prior to type parameters
   --> $DIR/suggest-move-lifetimes.rs:15:16
    |
 LL | struct D<T, U, 'a, 'b, V, 'c> {
-   |         -------^^--^^-----^^- help: reorder the parameters: lifetimes, then types, then consts: `<'a, 'b, 'c, T, U, V>`
+   |         -------^^--^^-----^^- help: reorder the parameters: lifetimes, then types: `<'a, 'b, 'c, T, U, V>`
 
 error: aborting due to 4 previous errors