Allow using named consts in pattern types

9 files changed, 186 insertions, 56 deletions

diff --git a/compiler/rustc_ast_lowering/src/pat.rs b/compiler/rustc_ast_lowering/src/pat.rs
index 57f15f99760..bb9b2a13185 100644
--- a/compiler/rustc_ast_lowering/src/pat.rs
+++ b/compiler/rustc_ast_lowering/src/pat.rs
@@ -440,17 +440,16 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         let node = loop {
             match &pattern.kind {
                 PatKind::Range(e1, e2, Spanned { node: end, .. }) => {
+                    // FIXME(pattern_types): remove this closure and call `lower_const_arg` instead.
+                    // That requires first modifying the AST to have const args here.
                     let mut lower_expr = |e: &Expr| -> &_ {
-                        let kind = if let ExprKind::Path(qself, path) = &e.kind {
-                            hir::ConstArgKind::Path(self.lower_qpath(
-                                e.id,
-                                qself,
-                                path,
-                                ParamMode::Optional,
-                                AllowReturnTypeNotation::No,
-                                ImplTraitContext::Disallowed(ImplTraitPosition::Path),
-                                None,
-                            ))
+                        if let ExprKind::Path(None, path) = &e.kind
+                            && let Some(res) = self
+                                .resolver
+                                .get_partial_res(e.id)
+                                .and_then(|partial_res| partial_res.full_res())
+                        {
+                            self.lower_const_path_to_const_arg(path, res, e.id, e.span)
                         } else {
                             let node_id = self.next_node_id();
                             let def_id = self.create_def(
@@ -467,9 +466,11 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                                 body: self.lower_const_body(pattern.span, Some(e)),
                                 span: self.lower_span(pattern.span),
                             });
-                            hir::ConstArgKind::Anon(ac)
-                        };
-                        self.arena.alloc(hir::ConstArg { hir_id: self.next_id(), kind })
+                            self.arena.alloc(hir::ConstArg {
+                                hir_id: self.next_id(),
+                                kind: hir::ConstArgKind::Anon(ac),
+                            })
+                        }
                     };
                     break hir::TyPatKind::Range(
                         e1.as_deref().map(|e| lower_expr(e)),
diff --git a/compiler/rustc_hir_analysis/src/collect/generics_of.rs b/compiler/rustc_hir_analysis/src/collect/generics_of.rs
index 2ac8acbd3a4..c0902398a54 100644
--- a/compiler/rustc_hir_analysis/src/collect/generics_of.rs
+++ b/compiler/rustc_hir_analysis/src/collect/generics_of.rs
@@ -198,6 +198,7 @@ pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Generics {
                     {
                         Some(parent_did)
                     }
+                    Node::TyPat(_) => Some(parent_did),
                     _ => None,
                 }
             }
diff --git a/tests/ui/type/pattern_types/assoc_const.default.stderr b/tests/ui/type/pattern_types/assoc_const.default.stderr
new file mode 100644
index 00000000000..abda40e4681
--- /dev/null
+++ b/tests/ui/type/pattern_types/assoc_const.default.stderr
@@ -0,0 +1,36 @@
+error: constant expression depends on a generic parameter
+  --> $DIR/assoc_const.rs:17:19
+   |
+LL | fn foo<T: Foo>(_: pattern_type!(u32 is <T as Foo>::START..=<T as Foo>::END)) {}
+   |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: this may fail depending on what value the parameter takes
+
+error: constant expression depends on a generic parameter
+  --> $DIR/assoc_const.rs:17:19
+   |
+LL | fn foo<T: Foo>(_: pattern_type!(u32 is <T as Foo>::START..=<T as Foo>::END)) {}
+   |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: this may fail depending on what value the parameter takes
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error: constant expression depends on a generic parameter
+  --> $DIR/assoc_const.rs:20:19
+   |
+LL | fn bar<T: Foo>(_: pattern_type!(u32 is T::START..=T::END)) {}
+   |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: this may fail depending on what value the parameter takes
+
+error: constant expression depends on a generic parameter
+  --> $DIR/assoc_const.rs:20:19
+   |
+LL | fn bar<T: Foo>(_: pattern_type!(u32 is T::START..=T::END)) {}
+   |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: this may fail depending on what value the parameter takes
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error: aborting due to 4 previous errors
+
diff --git a/tests/ui/type/pattern_types/assoc_const.rs b/tests/ui/type/pattern_types/assoc_const.rs
new file mode 100644
index 00000000000..af0f7e4cbf3
--- /dev/null
+++ b/tests/ui/type/pattern_types/assoc_const.rs
@@ -0,0 +1,24 @@
+#![feature(pattern_types)]
+#![feature(pattern_type_macro)]
+#![cfg_attr(const_arg, feature(generic_const_exprs))]
+#![expect(incomplete_features)]
+
+//@ revisions: default const_arg
+
+//@[const_arg] check-pass
+
+use std::pat::pattern_type;
+
+trait Foo {
+    const START: u32;
+    const END: u32;
+}
+
+fn foo<T: Foo>(_: pattern_type!(u32 is <T as Foo>::START..=<T as Foo>::END)) {}
+//[default]~^ ERROR: constant expression depends on a generic parameter
+//[default]~| ERROR: constant expression depends on a generic parameter
+fn bar<T: Foo>(_: pattern_type!(u32 is T::START..=T::END)) {}
+//[default]~^ ERROR: constant expression depends on a generic parameter
+//[default]~| ERROR: constant expression depends on a generic parameter
+
+fn main() {}
diff --git a/tests/ui/type/pattern_types/bad_const_generics_args_on_const_param.rs b/tests/ui/type/pattern_types/bad_const_generics_args_on_const_param.rs
index 05e308de7b1..0f10bf8ce62 100644
--- a/tests/ui/type/pattern_types/bad_const_generics_args_on_const_param.rs
+++ b/tests/ui/type/pattern_types/bad_const_generics_args_on_const_param.rs
@@ -1,11 +1,14 @@
+//@known-bug: #127972
+//@ failure-status: 101
+//@ normalize-stderr: "note: .*\n\n" -> ""
+//@ normalize-stderr: "thread 'rustc' panicked.*\n" -> ""
+//@ normalize-stderr: "(error: internal compiler error: [^:]+):\d+:\d+: " -> "$1:LL:CC: "
+//@ rustc-env:RUST_BACKTRACE=0
+
 #![feature(pattern_types, pattern_type_macro)]
 #![allow(internal_features)]
 
 type Pat<const START: u32, const END: u32> =
     std::pat::pattern_type!(u32 is START::<(), i32, 2>..=END::<_, Assoc = ()>);
-//~^ ERROR type and const arguments are not allowed on const parameter `START`
-//~| ERROR generic arguments are not allowed on const parameter `END`
-//~| ERROR associated item constraints are not allowed here
-//~| ERROR `_` is not allowed within types on item signatures for type aliases
 
 fn main() {}
diff --git a/tests/ui/type/pattern_types/bad_const_generics_args_on_const_param.stderr b/tests/ui/type/pattern_types/bad_const_generics_args_on_const_param.stderr
index c4ba89de3f3..fbe80a19863 100644
--- a/tests/ui/type/pattern_types/bad_const_generics_args_on_const_param.stderr
+++ b/tests/ui/type/pattern_types/bad_const_generics_args_on_const_param.stderr
@@ -1,44 +1,14 @@
-error[E0109]: type and const arguments are not allowed on const parameter `START`
-  --> $DIR/bad_const_generics_args_on_const_param.rs:5:44
+error: internal compiler error: compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs:LL:CC: try_lower_anon_const_lit: received const param which shouldn't be possible
+  --> $DIR/bad_const_generics_args_on_const_param.rs:12:36
    |
 LL |     std::pat::pattern_type!(u32 is START::<(), i32, 2>..=END::<_, Assoc = ()>);
-   |                                    -----   ^^  ^^^  ^ type and const arguments not allowed
-   |                                    |
-   |                                    not allowed on const parameter `START`
-   |
-note: const parameter `START` defined here
-  --> $DIR/bad_const_generics_args_on_const_param.rs:4:16
-   |
-LL | type Pat<const START: u32, const END: u32> =
-   |                ^^^^^
-
-error[E0109]: generic arguments are not allowed on const parameter `END`
-  --> $DIR/bad_const_generics_args_on_const_param.rs:5:64
-   |
-LL |     std::pat::pattern_type!(u32 is START::<(), i32, 2>..=END::<_, Assoc = ()>);
-   |                                                          ---   ^ generic argument not allowed
-   |                                                          |
-   |                                                          not allowed on const parameter `END`
-   |
-note: const parameter `END` defined here
-  --> $DIR/bad_const_generics_args_on_const_param.rs:4:34
-   |
-LL | type Pat<const START: u32, const END: u32> =
-   |                                  ^^^
-
-error[E0229]: associated item constraints are not allowed here
-  --> $DIR/bad_const_generics_args_on_const_param.rs:5:67
-   |
-LL |     std::pat::pattern_type!(u32 is START::<(), i32, 2>..=END::<_, Assoc = ()>);
-   |                                                                   ^^^^^^^^^^ associated item constraint not allowed here
+   |                                    ^^^^^^^^^^^^^^^^^^^
 
-error[E0121]: the placeholder `_` is not allowed within types on item signatures for type aliases
-  --> $DIR/bad_const_generics_args_on_const_param.rs:5:64
-   |
-LL |     std::pat::pattern_type!(u32 is START::<(), i32, 2>..=END::<_, Assoc = ()>);
-   |                                                                ^ not allowed in type signatures
 
-error: aborting due to 4 previous errors
+Box<dyn Any>
+query stack during panic:
+#0 [type_of] expanding type alias `Pat`
+#1 [check_well_formed] checking that `Pat` is well-formed
+... and 2 other queries... use `env RUST_BACKTRACE=1` to see the full query stack
+error: aborting due to 1 previous error
 
-Some errors have detailed explanations: E0109, E0121, E0229.
-For more information about an error, try `rustc --explain E0109`.
diff --git a/tests/ui/type/pattern_types/const_block.rs b/tests/ui/type/pattern_types/const_block.rs
new file mode 100644
index 00000000000..49c87f4fa0d
--- /dev/null
+++ b/tests/ui/type/pattern_types/const_block.rs
@@ -0,0 +1,10 @@
+#![feature(pattern_types)]
+#![feature(pattern_type_macro)]
+#![feature(inline_const_pat)]
+
+use std::pat::pattern_type;
+
+fn bar(x: pattern_type!(u32 is 0..=const{ 5 + 5 })) {}
+//~^ ERROR: cycle
+
+fn main() {}
diff --git a/tests/ui/type/pattern_types/const_block.stderr b/tests/ui/type/pattern_types/const_block.stderr
new file mode 100644
index 00000000000..82b616105af
--- /dev/null
+++ b/tests/ui/type/pattern_types/const_block.stderr
@@ -0,0 +1,72 @@
+error[E0391]: cycle detected when evaluating type-level constant
+  --> $DIR/const_block.rs:7:36
+   |
+LL | fn bar(x: pattern_type!(u32 is 0..=const{ 5 + 5 })) {}
+   |                                    ^^^^^^^^^^^^^^
+   |
+note: ...which requires const-evaluating + checking `bar::{constant#2}`...
+  --> $DIR/const_block.rs:7:36
+   |
+LL | fn bar(x: pattern_type!(u32 is 0..=const{ 5 + 5 })) {}
+   |                                    ^^^^^^^^^^^^^^
+note: ...which requires caching mir of `bar::{constant#2}` for CTFE...
+  --> $DIR/const_block.rs:7:36
+   |
+LL | fn bar(x: pattern_type!(u32 is 0..=const{ 5 + 5 })) {}
+   |                                    ^^^^^^^^^^^^^^
+note: ...which requires elaborating drops for `bar::{constant#2}`...
+  --> $DIR/const_block.rs:7:36
+   |
+LL | fn bar(x: pattern_type!(u32 is 0..=const{ 5 + 5 })) {}
+   |                                    ^^^^^^^^^^^^^^
+note: ...which requires borrow-checking `bar::{constant#2}`...
+  --> $DIR/const_block.rs:7:36
+   |
+LL | fn bar(x: pattern_type!(u32 is 0..=const{ 5 + 5 })) {}
+   |                                    ^^^^^^^^^^^^^^
+note: ...which requires borrow-checking `bar::{constant#0}`...
+  --> $DIR/const_block.rs:7:41
+   |
+LL | fn bar(x: pattern_type!(u32 is 0..=const{ 5 + 5 })) {}
+   |                                         ^^^^^^^^^
+note: ...which requires promoting constants in MIR for `bar::{constant#0}`...
+  --> $DIR/const_block.rs:7:41
+   |
+LL | fn bar(x: pattern_type!(u32 is 0..=const{ 5 + 5 })) {}
+   |                                         ^^^^^^^^^
+note: ...which requires const checking `bar::{constant#0}`...
+  --> $DIR/const_block.rs:7:41
+   |
+LL | fn bar(x: pattern_type!(u32 is 0..=const{ 5 + 5 })) {}
+   |                                         ^^^^^^^^^
+note: ...which requires building MIR for `bar::{constant#0}`...
+  --> $DIR/const_block.rs:7:41
+   |
+LL | fn bar(x: pattern_type!(u32 is 0..=const{ 5 + 5 })) {}
+   |                                         ^^^^^^^^^
+note: ...which requires match-checking `bar::{constant#0}`...
+  --> $DIR/const_block.rs:7:41
+   |
+LL | fn bar(x: pattern_type!(u32 is 0..=const{ 5 + 5 })) {}
+   |                                         ^^^^^^^^^
+note: ...which requires type-checking `bar::{constant#0}`...
+  --> $DIR/const_block.rs:7:41
+   |
+LL | fn bar(x: pattern_type!(u32 is 0..=const{ 5 + 5 })) {}
+   |                                         ^^^^^^^^^
+note: ...which requires type-checking `bar`...
+  --> $DIR/const_block.rs:7:1
+   |
+LL | fn bar(x: pattern_type!(u32 is 0..=const{ 5 + 5 })) {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   = note: ...which again requires evaluating type-level constant, completing the cycle
+note: cycle used when checking that `bar` is well-formed
+  --> $DIR/const_block.rs:7:1
+   |
+LL | fn bar(x: pattern_type!(u32 is 0..=const{ 5 + 5 })) {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   = note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0391`.
diff --git a/tests/ui/type/pattern_types/free_const.rs b/tests/ui/type/pattern_types/free_const.rs
new file mode 100644
index 00000000000..2e29fce2379
--- /dev/null
+++ b/tests/ui/type/pattern_types/free_const.rs
@@ -0,0 +1,13 @@
+//@ check-pass
+
+#![feature(pattern_types)]
+#![feature(pattern_type_macro)]
+
+use std::pat::pattern_type;
+
+const START: u32 = 0;
+const END: u32 = 10;
+
+fn foo(_: pattern_type!(u32 is START..=END)) {}
+
+fn main() {}