Auto merge of #70107 - lcnr:issue68977, r=eddyb

WF-check all ty::Const's, not just array lengths.

fixes #68977

This PR removes the special case for array length in `wf::compute` and
checks the well formedness of all consts.

Changes `PredicateKind::WellFormed` to take a `GenericArg` and updates `wf::obligations`.

src/test/ui/const-generics/cannot-infer-const-args.stderr

@@ -11,7 +11,9 @@ error[E0282]: type annotations needed
   --> $DIR/cannot-infer-const-args.rs:9:5
    |
 LL |     foo();
-   |     ^^^ cannot infer type for fn item `fn() -> usize {foo::<{_: usize}>}`
+   |     ^^^
+   |
+   = note: unable to infer the value of a const parameter
 
 error: aborting due to previous error; 1 warning emitted
 

src/test/ui/const-generics/issues/issue-61747.rs

@@ -1,5 +1,3 @@
-// check-pass
-
 #![feature(const_generics)]
 //~^ WARN the feature `const_generics` is incomplete
 
@@ -7,6 +5,7 @@ struct Const<const N: usize>;
 
 impl<const C: usize> Const<{C}> {
     fn successor() -> Const<{C + 1}> {
+        //~^ ERROR constant expression depends on a generic parameter
         Const
     }
 }

src/test/ui/const-generics/issues/issue-61747.stderr

@@ -1,5 +1,5 @@
 warning: the feature `const_generics` is incomplete and may not be safe to use and/or cause compiler crashes
-  --> $DIR/issue-61747.rs:3:12
+  --> $DIR/issue-61747.rs:1:12
    |
 LL | #![feature(const_generics)]
    |            ^^^^^^^^^^^^^^
@@ -7,5 +7,13 @@ LL | #![feature(const_generics)]
    = note: `#[warn(incomplete_features)]` on by default
    = note: see issue #44580 <https://github.com/rust-lang/rust/issues/44580> for more information
 
-warning: 1 warning emitted
+error: constant expression depends on a generic parameter
+  --> $DIR/issue-61747.rs:7:23
+   |
+LL |     fn successor() -> Const<{C + 1}> {
+   |                       ^^^^^^^^^^^^^^
+   |
+   = note: this may fail depending on what value the parameter takes
+
+error: aborting due to previous error; 1 warning emitted
 

src/test/ui/const-generics/issues/issue-61935.rs

@@ -1,5 +1,3 @@
-// check-pass
-
 #![feature(const_generics)]
 //~^ WARN the feature `const_generics` is incomplete
 
@@ -8,6 +6,7 @@ trait Foo {}
 impl<const N: usize> Foo for [(); N]
     where
         Self:FooImpl<{N==0}>
+//~^ERROR constant expression depends on a generic parameter
 {}
 
 trait FooImpl<const IS_ZERO: bool>{}

src/test/ui/const-generics/issues/issue-61935.stderr

@@ -1,5 +1,5 @@
 warning: the feature `const_generics` is incomplete and may not be safe to use and/or cause compiler crashes
-  --> $DIR/issue-61935.rs:3:12
+  --> $DIR/issue-61935.rs:1:12
    |
 LL | #![feature(const_generics)]
    |            ^^^^^^^^^^^^^^
@@ -7,5 +7,13 @@ LL | #![feature(const_generics)]
    = note: `#[warn(incomplete_features)]` on by default
    = note: see issue #44580 <https://github.com/rust-lang/rust/issues/44580> for more information
 
-warning: 1 warning emitted
+error: constant expression depends on a generic parameter
+  --> $DIR/issue-61935.rs:8:14
+   |
+LL |         Self:FooImpl<{N==0}>
+   |              ^^^^^^^^^^^^^^^
+   |
+   = note: this may fail depending on what value the parameter takes
+
+error: aborting due to previous error; 1 warning emitted
 

src/test/ui/const-generics/issues/issue-62220.rs

@@ -1,7 +1,6 @@
-// build-pass
 #![allow(incomplete_features)]
-
 #![feature(const_generics)]
+
 pub struct Vector<T, const N: usize>([T; N]);
 
 pub type TruncatedVector<T, const N: usize> = Vector<T, { N - 1 }>;
@@ -9,6 +8,7 @@ pub type TruncatedVector<T, const N: usize> = Vector<T, { N - 1 }>;
 impl<T, const N: usize> Vector<T, { N }> {
     /// Drop the last component and return the vector with one fewer dimension.
     pub fn trunc(self) -> (TruncatedVector<T, { N }>, T) {
+        //~^ ERROR constant expression depends on a generic parameter
         unimplemented!()
     }
 }

src/test/ui/const-generics/issues/issue-62220.stderr

@@ -0,0 +1,10 @@
+error: constant expression depends on a generic parameter
+  --> $DIR/issue-62220.rs:10:27
+   |
+LL |     pub fn trunc(self) -> (TruncatedVector<T, { N }>, T) {
+   |                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: this may fail depending on what value the parameter takes
+
+error: aborting due to previous error
+

src/test/ui/const-generics/issues/issue-66205.rs

@@ -1,6 +1,6 @@
-#![allow(incomplete_features, dead_code, unconditional_recursion)]
+#![allow(dead_code, unconditional_recursion)]
 #![feature(const_generics)]
-#![feature(lazy_normalization_consts)]
+//~^ WARN the feature `const_generics` is incomplete
 
 fn fact<const N: usize>() {
     fact::<{ N - 1 }>();

src/test/ui/const-generics/issues/issue-66205.stderr

@@ -1,3 +1,12 @@
+warning: the feature `const_generics` is incomplete and may not be safe to use and/or cause compiler crashes
+  --> $DIR/issue-66205.rs:2:12
+   |
+LL | #![feature(const_generics)]
+   |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
+   = note: see issue #44580 <https://github.com/rust-lang/rust/issues/44580> for more information
+
 error: constant expression depends on a generic parameter
   --> $DIR/issue-66205.rs:6:12
    |
@@ -6,5 +15,5 @@ LL |     fact::<{ N - 1 }>();
    |
    = note: this may fail depending on what value the parameter takes
 
-error: aborting due to previous error
+error: aborting due to previous error; 1 warning emitted
 

src/test/ui/const-generics/issues/issue-68977.rs

@@ -0,0 +1,40 @@
+#![feature(const_generics)]
+//~^ WARN the feature `const_generics` is incomplete
+
+struct PhantomU8<const X: u8>;
+
+trait FxpStorage {
+    type SInt; // Add arithmetic traits as needed.
+}
+
+macro_rules! fxp_storage_impls {
+    ($($($n:literal)|+ => $sint:ty),* $(,)?) => {
+        $($(impl FxpStorage for PhantomU8<$n> {
+            type SInt = $sint;
+        })*)*
+    }
+}
+
+fxp_storage_impls! {
+    1 => i8,
+    2 => i16,
+    3 | 4 => i32,
+    5 | 6 | 7 | 8 => i64,
+    9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 => i128,
+}
+
+type FxpStorageHelper<const INT_BITS: u8, const FRAC_BITS: u8> =
+    PhantomU8<{(INT_BITS + FRAC_BITS + 7) / 8}>;
+
+struct Fxp<const INT_BITS: u8, const FRAC_BITS: u8>
+where
+    FxpStorageHelper<INT_BITS, FRAC_BITS>: FxpStorage,
+    //~^ ERROR constant expression depends on a generic parameter
+{
+    storage: <FxpStorageHelper<INT_BITS, FRAC_BITS> as FxpStorage>::SInt,
+}
+
+fn main() {
+    Fxp::<1, 15> { storage: 0i16 };
+    Fxp::<2, 15> { storage: 0i32 };
+}

src/test/ui/const-generics/issues/issue-68977.stderr

@@ -0,0 +1,19 @@
+warning: the feature `const_generics` is incomplete and may not be safe to use and/or cause compiler crashes
+  --> $DIR/issue-68977.rs:1:12
+   |
+LL | #![feature(const_generics)]
+   |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
+   = note: see issue #44580 <https://github.com/rust-lang/rust/issues/44580> for more information
+
+error: constant expression depends on a generic parameter
+  --> $DIR/issue-68977.rs:31:44
+   |
+LL |     FxpStorageHelper<INT_BITS, FRAC_BITS>: FxpStorage,
+   |                                            ^^^^^^^^^^
+   |
+   = note: this may fail depending on what value the parameter takes
+
+error: aborting due to previous error; 1 warning emitted
+

src/test/ui/const-generics/lazy-normalization/issue-71922.rs

@@ -1,9 +1,9 @@
-// run-pass
 #![feature(const_generics)]
-#![allow(incomplete_features)]
+//~^ WARN the feature `const_generics` is incomplete
 trait Foo {}
 
 impl<const N: usize> Foo for [(); N] where Self: FooImpl<{ N == 0 }> {}
+//~^ ERROR constant expression depends on a generic parameter
 
 trait FooImpl<const IS_ZERO: bool> {}
 

src/test/ui/const-generics/lazy-normalization/issue-71922.stderr

@@ -0,0 +1,19 @@
+warning: the feature `const_generics` is incomplete and may not be safe to use and/or cause compiler crashes
+  --> $DIR/issue-71922.rs:1:12
+   |
+LL | #![feature(const_generics)]
+   |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
+   = note: see issue #44580 <https://github.com/rust-lang/rust/issues/44580> for more information
+
+error: constant expression depends on a generic parameter
+  --> $DIR/issue-71922.rs:5:50
+   |
+LL | impl<const N: usize> Foo for [(); N] where Self: FooImpl<{ N == 0 }> {}
+   |                                                  ^^^^^^^^^^^^^^^^^^^
+   |
+   = note: this may fail depending on what value the parameter takes
+
+error: aborting due to previous error; 1 warning emitted
+

src/test/ui/const-generics/wf-misc.rs

@@ -0,0 +1,16 @@
+#![feature(const_generics)]
+//~^ WARN the feature `const_generics` is incomplete
+
+pub fn arr_len<const N: usize>() {
+    let _: [u8; N + 1];
+    //~^ ERROR constant expression depends on a generic parameter
+}
+
+struct Const<const N: usize>;
+
+pub fn func_call<const N: usize>() {
+    let _: Const::<{N + 1}>;
+    //~^ ERROR constant expression depends on a generic parameter
+}
+
+fn main() {}

src/test/ui/const-generics/wf-misc.stderr

@@ -0,0 +1,27 @@
+warning: the feature `const_generics` is incomplete and may not be safe to use and/or cause compiler crashes
+  --> $DIR/wf-misc.rs:1:12
+   |
+LL | #![feature(const_generics)]
+   |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
+   = note: see issue #44580 <https://github.com/rust-lang/rust/issues/44580> for more information
+
+error: constant expression depends on a generic parameter
+  --> $DIR/wf-misc.rs:5:12
+   |
+LL |     let _: [u8; N + 1];
+   |            ^^^^^^^^^^^
+   |
+   = note: this may fail depending on what value the parameter takes
+
+error: constant expression depends on a generic parameter
+  --> $DIR/wf-misc.rs:12:12
+   |
+LL |     let _: Const::<{N + 1}>;
+   |            ^^^^^^^^^^^^^^^^
+   |
+   = note: this may fail depending on what value the parameter takes
+
+error: aborting due to 2 previous errors; 1 warning emitted
+