typeck: always expose repeat count AnonConsts' parent in generics_of.

Author: eddyb

src/librustc_typeck/collect.rs

@@ -1170,14 +1170,28 @@ fn generics_of(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::Generics {
         }
         // FIXME(#43408) enable this always when we get lazy normalization.
         Node::AnonConst(_) => {
+            let parent_id = tcx.hir().get_parent_item(hir_id);
+            let parent_def_id = tcx.hir().local_def_id(parent_id);
+
             // HACK(eddyb) this provides the correct generics when
             // `feature(const_generics)` is enabled, so that const expressions
             // used with const generics, e.g. `Foo<{N+1}>`, can work at all.
             if tcx.features().const_generics {
-                let parent_id = tcx.hir().get_parent_item(hir_id);
-                Some(tcx.hir().local_def_id(parent_id))
+                Some(parent_def_id)
             } else {
-                None
+                let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id));
+                match parent_node {
+                    // HACK(eddyb) this provides the correct generics for repeat
+                    // expressions' count (i.e. `N` in `[x; N]`), as they shouldn't
+                    // be able to cause query cycle errors.
+                    Node::Expr(&Expr { kind: ExprKind::Repeat(_, ref constant), .. })
+                        if constant.hir_id == hir_id =>
+                    {
+                        Some(parent_def_id)
+                    }
+
+                    _ => None,
+                }
             }
         }
         Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {

src/test/ui/associated-const/associated-const-type-parameter-arrays-2.rs

@@ -14,7 +14,7 @@ impl Foo for Def {
 
 pub fn test<A: Foo, B: Foo>() {
     let _array = [4; <A as Foo>::Y];
-    //~^ ERROR the trait bound `A: Foo` is not satisfied [E0277]
+    //~^ ERROR constant expression depends on a generic parameter
 }
 
 fn main() {

src/test/ui/associated-const/associated-const-type-parameter-arrays-2.stderr

@@ -1,17 +1,10 @@
-error[E0277]: the trait bound `A: Foo` is not satisfied
+error: constant expression depends on a generic parameter
   --> $DIR/associated-const-type-parameter-arrays-2.rs:16:22
    |
-LL |     const Y: usize;
-   |     --------------- required by `Foo::Y`
-...
 LL |     let _array = [4; <A as Foo>::Y];
-   |                      ^^^^^^^^^^^^^ the trait `Foo` is not implemented for `A`
+   |                      ^^^^^^^^^^^^^
    |
-help: consider further restricting this bound
-   |
-LL | pub fn test<A: Foo + Foo, B: Foo>() {
-   |                    ^^^^^
+   = note: this may fail depending on what value the parameter takes
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0277`.

src/test/ui/consts/too_generic_eval_ice.rs

@@ -4,10 +4,9 @@ impl<A, B> Foo<A, B> {
     const HOST_SIZE: usize = std::mem::size_of::<B>();
 
     pub fn crash() -> bool {
-        [5; Self::HOST_SIZE] == [6; 0] //~ ERROR no associated item named `HOST_SIZE`
-        //~^ the size for values of type `A` cannot be known
-        //~| the size for values of type `B` cannot be known
-        //~| binary operation `==` cannot be applied to type `[{integer}; _]`
+        [5; Self::HOST_SIZE] == [6; 0]
+        //~^ ERROR constant expression depends on a generic parameter
+        //~| ERROR binary operation `==` cannot be applied to type `[{integer}; _]`
     }
 }
 

src/test/ui/consts/too_generic_eval_ice.stderr

@@ -1,45 +1,10 @@
-error[E0599]: no associated item named `HOST_SIZE` found for struct `Foo<A, B>` in the current scope
-  --> $DIR/too_generic_eval_ice.rs:7:19
-   |
-LL | pub struct Foo<A, B>(A, B);
-   | --------------------------- associated item `HOST_SIZE` not found for this
-...
-LL |         [5; Self::HOST_SIZE] == [6; 0]
-   |                   ^^^^^^^^^ associated item not found in `Foo<A, B>`
-   |
-   = note: the method `HOST_SIZE` exists but the following trait bounds were not satisfied:
-           `A: std::marker::Sized`
-           `B: std::marker::Sized`
-
-error[E0277]: the size for values of type `A` cannot be known at compilation time
-  --> $DIR/too_generic_eval_ice.rs:7:13
-   |
-LL | pub struct Foo<A, B>(A, B);
-   |                - required by this bound in `Foo`
-LL | 
-LL | impl<A, B> Foo<A, B> {
-   |      - this type parameter needs to be `std::marker::Sized`
-...
-LL |         [5; Self::HOST_SIZE] == [6; 0]
-   |             ^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
-   |
-   = help: the trait `std::marker::Sized` is not implemented for `A`
-   = note: to learn more, visit <https://doc.rust-lang.org/book/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
-
-error[E0277]: the size for values of type `B` cannot be known at compilation time
+error: constant expression depends on a generic parameter
   --> $DIR/too_generic_eval_ice.rs:7:13
    |
-LL | pub struct Foo<A, B>(A, B);
-   |                   - required by this bound in `Foo`
-LL | 
-LL | impl<A, B> Foo<A, B> {
-   |         - this type parameter needs to be `std::marker::Sized`
-...
 LL |         [5; Self::HOST_SIZE] == [6; 0]
-   |             ^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
+   |             ^^^^^^^^^^^^^^^
    |
-   = help: the trait `std::marker::Sized` is not implemented for `B`
-   = note: to learn more, visit <https://doc.rust-lang.org/book/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
+   = note: this may fail depending on what value the parameter takes
 
 error[E0369]: binary operation `==` cannot be applied to type `[{integer}; _]`
   --> $DIR/too_generic_eval_ice.rs:7:30
@@ -49,7 +14,6 @@ LL |         [5; Self::HOST_SIZE] == [6; 0]
    |         |
    |         [{integer}; _]
 
-error: aborting due to 4 previous errors
+error: aborting due to 2 previous errors
 
-Some errors have detailed explanations: E0277, E0369, E0599.
-For more information about an error, try `rustc --explain E0277`.
+For more information about this error, try `rustc --explain E0369`.

src/test/ui/issues/issue-39211.rs

@@ -8,7 +8,8 @@ trait Mat {
 }
 
 fn m<M: Mat>() {
-    let a = [3; M::Row::DIM]; //~ ERROR associated type `Row` not found for `M`
+    let a = [3; M::Row::DIM];
+    //~^ ERROR constant expression depends on a generic parameter
 }
 fn main() {
 }

src/test/ui/issues/issue-39211.stderr

@@ -1,9 +1,10 @@
-error[E0220]: associated type `Row` not found for `M`
-  --> $DIR/issue-39211.rs:11:20
+error: constant expression depends on a generic parameter
+  --> $DIR/issue-39211.rs:11:17
    |
 LL |     let a = [3; M::Row::DIM];
-   |                    ^^^ associated type `Row` not found
+   |                 ^^^^^^^^^^^
+   |
+   = note: this may fail depending on what value the parameter takes
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0220`.