error on unsized AnonConsts

compiler/rustc_hir_typeck/src/lib.rs

@@ -200,6 +200,14 @@ fn typeck_with_inspect<'tcx>(
         let wf_code = ObligationCauseCode::WellFormed(Some(WellFormedLoc::Ty(def_id)));
         fcx.register_wf_obligation(expected_type.into(), body.value.span, wf_code);
 
+        if let hir::Node::AnonConst(_) = node {
+            fcx.require_type_is_sized(
+                expected_type,
+                body.value.span,
+                ObligationCauseCode::SizedConstOrStatic,
+            );
+        }
+
         fcx.check_expr_coercible_to_type(body.value, expected_type, None);
 
         fcx.write_ty(id, expected_type);

tests/ui/const-generics/adt_const_params/unsized-anon-const-err-1.rs

@@ -0,0 +1,22 @@
+// regression test for issue #137582, where constant evaluating an unsized AnonConst would ICE
+
+#![feature(adt_const_params)]
+
+mod lib {
+    pub type Matrix = [&'static u32];
+
+    const EMPTY_MATRIX: Matrix = [[0; 4]; 4];
+    //~^ ERROR the size for values of type `[&'static u32]` cannot be known at compilation time
+    //~| ERROR mismatched types
+    //~| ERROR mismatched types
+
+    pub struct Walk<const CURRENT: usize, const REMAINING: Matrix> {
+        //~^ ERROR use of unstable library feature `unsized_const_params`
+        _p: (),
+    }
+
+    impl<const CURRENT: usize> Walk<CURRENT, EMPTY_MATRIX> {}
+    //~^ ERROR the size for values of type `[&'static u32]` cannot be known at compilation time
+}
+
+fn main() {}

tests/ui/const-generics/adt_const_params/unsized-anon-const-err-1.stderr

@@ -0,0 +1,44 @@
+error[E0277]: the size for values of type `[&'static u32]` cannot be known at compilation time
+  --> $DIR/unsized-anon-const-err-1.rs:8:25
+   |
+LL |     const EMPTY_MATRIX: Matrix = [[0; 4]; 4];
+   |                         ^^^^^^ doesn't have a size known at compile-time
+   |
+   = help: the trait `Sized` is not implemented for `[&'static u32]`
+   = note: statics and constants must have a statically known size
+
+error[E0658]: use of unstable library feature `unsized_const_params`
+  --> $DIR/unsized-anon-const-err-1.rs:13:43
+   |
+LL |     pub struct Walk<const CURRENT: usize, const REMAINING: Matrix> {
+   |                                           ^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = help: add `#![feature(unsized_const_params)]` to the crate attributes to enable
+   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+   = note: required for `[&'static u32]` to implement `ConstParamTy_`
+
+error[E0277]: the size for values of type `[&'static u32]` cannot be known at compilation time
+  --> $DIR/unsized-anon-const-err-1.rs:18:46
+   |
+LL |     impl<const CURRENT: usize> Walk<CURRENT, EMPTY_MATRIX> {}
+   |                                              ^^^^^^^^^^^^ doesn't have a size known at compile-time
+   |
+   = help: the trait `Sized` is not implemented for `[&'static u32]`
+   = note: statics and constants must have a statically known size
+
+error[E0308]: mismatched types
+  --> $DIR/unsized-anon-const-err-1.rs:8:35
+   |
+LL |     const EMPTY_MATRIX: Matrix = [[0; 4]; 4];
+   |                                   ^^^^^^ expected `&u32`, found `[{integer}; 4]`
+
+error[E0308]: mismatched types
+  --> $DIR/unsized-anon-const-err-1.rs:8:34
+   |
+LL |     const EMPTY_MATRIX: Matrix = [[0; 4]; 4];
+   |                                  ^^^^^^^^^^^ expected `[&u32]`, found `[&u32; 4]`
+
+error: aborting due to 5 previous errors
+
+Some errors have detailed explanations: E0277, E0308, E0658.
+For more information about an error, try `rustc --explain E0277`.

tests/ui/const-generics/adt_const_params/unsized-anon-const-err-2.rs

@@ -0,0 +1,21 @@
+// regression test for issue #151591, where constant evaluating an unsized AnonConst would ICE
+
+#![feature(adt_const_params)]
+#![feature(unsized_const_params)]
+//~^ WARN the feature `unsized_const_params` is incomplete and may not be safe to use and/or cause compiler crashes
+
+#[derive(Clone)]
+struct S<const L: [u8]>;
+
+const A: [u8];
+//~^ ERROR free constant item without body
+//~| ERROR the size for values of type `[u8]` cannot be known at compilation time
+
+impl<const N: i32> Copy for S<A> {}
+//~^ ERROR the size for values of type `[u8]` cannot be known at compilation time
+//~| ERROR the const parameter `N` is not constrained by the impl trait, self type, or predicates
+impl<const M: usize> Copy for S<A> {}
+//~^ ERROR the size for values of type `[u8]` cannot be known at compilation time
+//~| ERROR the const parameter `M` is not constrained by the impl trait, self type, or predicates
+
+fn main() {}

tests/ui/const-generics/adt_const_params/unsized-anon-const-err-2.stderr

@@ -0,0 +1,66 @@
+error: free constant item without body
+  --> $DIR/unsized-anon-const-err-2.rs:10:1
+   |
+LL | const A: [u8];
+   | ^^^^^^^^^^^^^-
+   |              |
+   |              help: provide a definition for the constant: `= <expr>;`
+
+warning: the feature `unsized_const_params` is incomplete and may not be safe to use and/or cause compiler crashes
+  --> $DIR/unsized-anon-const-err-2.rs:4:12
+   |
+LL | #![feature(unsized_const_params)]
+   |            ^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #95174 <https://github.com/rust-lang/rust/issues/95174> for more information
+   = note: `#[warn(incomplete_features)]` on by default
+
+error[E0277]: the size for values of type `[u8]` cannot be known at compilation time
+  --> $DIR/unsized-anon-const-err-2.rs:10:10
+   |
+LL | const A: [u8];
+   |          ^^^^ doesn't have a size known at compile-time
+   |
+   = help: the trait `Sized` is not implemented for `[u8]`
+   = note: statics and constants must have a statically known size
+
+error[E0277]: the size for values of type `[u8]` cannot be known at compilation time
+  --> $DIR/unsized-anon-const-err-2.rs:14:31
+   |
+LL | impl<const N: i32> Copy for S<A> {}
+   |                               ^ doesn't have a size known at compile-time
+   |
+   = help: the trait `Sized` is not implemented for `[u8]`
+   = note: statics and constants must have a statically known size
+
+error[E0277]: the size for values of type `[u8]` cannot be known at compilation time
+  --> $DIR/unsized-anon-const-err-2.rs:17:33
+   |
+LL | impl<const M: usize> Copy for S<A> {}
+   |                                 ^ doesn't have a size known at compile-time
+   |
+   = help: the trait `Sized` is not implemented for `[u8]`
+   = note: statics and constants must have a statically known size
+
+error[E0207]: the const parameter `N` is not constrained by the impl trait, self type, or predicates
+  --> $DIR/unsized-anon-const-err-2.rs:14:6
+   |
+LL | impl<const N: i32> Copy for S<A> {}
+   |      ^^^^^^^^^^^^ unconstrained const parameter
+   |
+   = note: expressions using a const parameter must map each value to a distinct output value
+   = note: proving the result of expressions other than the parameter are unique is not supported
+
+error[E0207]: the const parameter `M` is not constrained by the impl trait, self type, or predicates
+  --> $DIR/unsized-anon-const-err-2.rs:17:6
+   |
+LL | impl<const M: usize> Copy for S<A> {}
+   |      ^^^^^^^^^^^^^^ unconstrained const parameter
+   |
+   = note: expressions using a const parameter must map each value to a distinct output value
+   = note: proving the result of expressions other than the parameter are unique is not supported
+
+error: aborting due to 6 previous errors; 1 warning emitted
+
+Some errors have detailed explanations: E0207, E0277.
+For more information about an error, try `rustc --explain E0207`.

tests/ui/const-generics/adt_const_params/unsized-anon-const-func-err.rs

@@ -0,0 +1,16 @@
+// manually reduced reproduction of issue #137582, where constant evaluating an unsized AnonConst
+// would ICE
+
+#![feature(adt_const_params)]
+
+fn func<const V: [u32]>() {}
+//~^ ERROR use of unstable library feature `unsized_const_params`
+
+const VALUE: [u32] = [0; 4];
+//~^ ERROR mismatched types
+//~| ERROR the size for values of type `[u32]` cannot be known at compilation time
+
+fn main() {
+    func::<VALUE>();
+    //~^ ERROR the size for values of type `[u32]` cannot be known at compilation time
+}

tests/ui/const-generics/adt_const_params/unsized-anon-const-func-err.stderr

@@ -0,0 +1,38 @@
+error[E0658]: use of unstable library feature `unsized_const_params`
+  --> $DIR/unsized-anon-const-func-err.rs:6:9
+   |
+LL | fn func<const V: [u32]>() {}
+   |         ^^^^^^^^^^^^^^
+   |
+   = help: add `#![feature(unsized_const_params)]` to the crate attributes to enable
+   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+   = note: required for `[u32]` to implement `ConstParamTy_`
+
+error[E0277]: the size for values of type `[u32]` cannot be known at compilation time
+  --> $DIR/unsized-anon-const-func-err.rs:9:14
+   |
+LL | const VALUE: [u32] = [0; 4];
+   |              ^^^^^ doesn't have a size known at compile-time
+   |
+   = help: the trait `Sized` is not implemented for `[u32]`
+   = note: statics and constants must have a statically known size
+
+error[E0308]: mismatched types
+  --> $DIR/unsized-anon-const-func-err.rs:9:22
+   |
+LL | const VALUE: [u32] = [0; 4];
+   |                      ^^^^^^ expected `[u32]`, found `[u32; 4]`
+
+error[E0277]: the size for values of type `[u32]` cannot be known at compilation time
+  --> $DIR/unsized-anon-const-func-err.rs:14:12
+   |
+LL |     func::<VALUE>();
+   |            ^^^^^ doesn't have a size known at compile-time
+   |
+   = help: the trait `Sized` is not implemented for `[u32]`
+   = note: statics and constants must have a statically known size
+
+error: aborting due to 4 previous errors
+
+Some errors have detailed explanations: E0277, E0308, E0658.
+For more information about an error, try `rustc --explain E0277`.

tests/ui/const-generics/adt_const_params/unsized-anon-const-struct-err.rs

@@ -0,0 +1,16 @@
+// manually reduced reproduction of issue #137582, where constant evaluating an unsized AnonConst
+// would ICE
+
+#![feature(adt_const_params)]
+
+const VALUE: [u32] = [0; 4];
+//~^ ERROR the size for values of type `[u32]` cannot be known at compilation time
+//~| ERROR mismatched types
+
+struct SomeStruct<const V: [u32]> {}
+//~^ ERROR use of unstable library feature `unsized_const_params`
+
+impl SomeStruct<VALUE> {}
+//~^ ERROR the size for values of type `[u32]` cannot be known at compilation time
+
+fn main() {}

tests/ui/const-generics/adt_const_params/unsized-anon-const-struct-err.stderr

@@ -0,0 +1,38 @@
+error[E0277]: the size for values of type `[u32]` cannot be known at compilation time
+  --> $DIR/unsized-anon-const-struct-err.rs:6:14
+   |
+LL | const VALUE: [u32] = [0; 4];
+   |              ^^^^^ doesn't have a size known at compile-time
+   |
+   = help: the trait `Sized` is not implemented for `[u32]`
+   = note: statics and constants must have a statically known size
+
+error[E0658]: use of unstable library feature `unsized_const_params`
+  --> $DIR/unsized-anon-const-struct-err.rs:10:19
+   |
+LL | struct SomeStruct<const V: [u32]> {}
+   |                   ^^^^^^^^^^^^^^
+   |
+   = help: add `#![feature(unsized_const_params)]` to the crate attributes to enable
+   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+   = note: required for `[u32]` to implement `ConstParamTy_`
+
+error[E0277]: the size for values of type `[u32]` cannot be known at compilation time
+  --> $DIR/unsized-anon-const-struct-err.rs:13:17
+   |
+LL | impl SomeStruct<VALUE> {}
+   |                 ^^^^^ doesn't have a size known at compile-time
+   |
+   = help: the trait `Sized` is not implemented for `[u32]`
+   = note: statics and constants must have a statically known size
+
+error[E0308]: mismatched types
+  --> $DIR/unsized-anon-const-struct-err.rs:6:22
+   |
+LL | const VALUE: [u32] = [0; 4];
+   |                      ^^^^^^ expected `[u32]`, found `[u32; 4]`
+
+error: aborting due to 4 previous errors
+
+Some errors have detailed explanations: E0277, E0308, E0658.
+For more information about an error, try `rustc --explain E0277`.