Improve errors on const mismatches #90987

b-naber · 2021-11-17T19:19:24Z

This allows us to suggest a correct anonymous constant in case there's a mismatch, e.g. in:

trait Trait {}
struct HasCastInTraitImpl<const N: usize, const M: usize>;
impl<const M: usize> Trait for HasCastInTraitImpl<M, { M + 1 }> {}
pub struct HasTrait<T: Trait>(T);
fn foo<const N: usize>() -> HasTrait<HasCastInTraitImpl<{ N + 1 }, { N + 1}>> { loop {} }

we now get a mismatch const error of the following form:

error[E0308]: mismatched types
  --> $DIR/mismatched-const-errors.rs:15:30
   |
LL | fn foo2<const N: usize>() -> HasTrait<HasCastInTraitImpl<{ N + 1}, { N + 1 }>> {
   |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `{ N + 1 }`, found `{ N + 1 + 1 }`
   |
   = note: expected type `{ N + 1 }`
              found type `{ N + 1 + 1 }`

instead of the found { M + 1 } constant that was previously output.

rust-highfive · 2021-11-17T19:19:27Z

r? @jackh726

(rust-highfive has picked a reviewer for you, use r? to override)

b-naber · 2021-11-17T19:19:43Z

r? @BoxyUwU

src/test/ui/const-generics/mismatched-const-errors.rs

BoxyUwU · 2021-11-17T20:54:39Z

src/test/ui/const-generics/mismatched-const-errors.stderr

+LL | fn foo5<const N: usize>() -> HasTrait<HasCastInTraitImpl<{ N + N }, { 2 * N }>> {
+   |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = help: try adding a `where` bound using this expression: `where [(); { M + 1 }]:`


I think this needs updating to print out with substs applied too

b-naber · 2021-11-18T14:50:07Z

Don't see why CI fails, I did bless those tests.

BoxyUwU · 2021-11-18T23:51:38Z

Can you check if this handles precedence right 🤔
if we have a const mismatch of like 3 * 2 + N and 3 * M where M is 2 + N i.e.

fn foo<const M: usize>() -> [(); 3 * M];
let _: [(); 3 * 2 + N] foo::<{ 2 + N }>();

do we get a silly error message like expected `3 * 2 + N` found `3 * 2 + N`

b-naber · 2021-11-19T18:07:39Z

yeah we do, but I think it shouldn't be too hard to include precedence of operations here when constructing the suggestion. I can try that.

bors · 2021-11-21T13:59:53Z

☔ The latest upstream changes (presumably #91104) made this pull request unmergeable. Please resolve the merge conflicts.

b-naber · 2021-11-23T18:02:19Z

Taking precedence into account when applying substitutions is anything but straightforward. I'd prefer to do this in another PR, since this is basically more effort than the original PR.

For now I'd suggest we just fall back to the unsubstituted suggestion, in case we would output the same suggestion as the error.

b-naber · 2021-11-23T18:17:34Z

@BoxyUwU Would that be ok for you?

b-naber · 2021-11-24T16:55:40Z

Did decide to implement this, wasn't as hard as I initially thought.

b-naber · 2021-11-25T15:50:31Z

Ok, I only blessed the tests in ui/const-generics, but they all passed in that CI run. So it seems as if for some reason the try_create_suggestion_for_mismatched_const call returns None in CI, but Some(suggestion) locally on my machine. I'm completely flabbergasted as to why that might be. Is const-generics somehow platform dependent?

bors · 2021-12-16T14:45:36Z

☔ The latest upstream changes (presumably #91996) made this pull request unmergeable. Please resolve the merge conflicts.

BoxyUwU · 2021-12-21T12:49:15Z

compiler/rustc_trait_selection/src/traits/const_evaluatable.rs

+                ty::ConstKind::Value(ConstValue::Scalar(scalar)) => match scalar.to_i64() {
+                    Ok(s) => {
+                        let s = format!("{}", s);
+
+                        if applied_subst {
+                            return Some(PrintStyle::Braces(None, s));
+                        } else {
+                            return Some(PrintStyle::NoBraces(s));
+                        }
+                    }
+                    Err(_) => return None,
+                },


This is the cause of the CI failures. the CI is failing on 32 bit stuff which means if we have a usize scalar here and call .to_i64 we get an InterpErrorInfo(InterpErrorInfoInner { kind: scalar size mismatch: expected 8 bytes but got 4 bytes instead, backtrace: None }) from this call but on 64bit it works fine because the sizes match.

the docs for to_i64 say "Fails if the scalar is a pointer" but I guess that is wrong .-.
this code would also just be wrong if the scalar was a u128 or something since those values cant all fit in a i128

not sure exactly what the right thing to replace this with is but we surely have code somewhere for printing this out

Thanks, that's a great catch. I'll try to figure out how to handle this correctly here.

…TooGeneric cases

…able error message

b-naber · 2021-12-24T14:37:53Z

For some reason I had to add the Cargo.lock file during the rebase (otherwise it wouldn't allow the rebase to continue). This seems to cause problems with CI now. What am I supposed to do here?

rust-log-analyzer · 2021-12-28T11:53:08Z

The job x86_64-gnu-llvm-12 failed! Check out the build log: (web) (plain)

Click to see the possible cause of the failure (guessed by this bot)

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---

---- [ui] ui/const-generics/defaults/generic-expr-default.rs stdout ----
diff of stderr:

4 LL | pub fn needs_evaluatable_bound<const N1: usize>() -> Foo<N1> {
6    |
6    |
-    = help: try adding a `where` bound using this expression: `where [(); { N1 + 1 }]:`
Some tests failed in compiletest suite=ui mode=ui host=x86_64-unknown-linux-gnu target=i686-unknown-linux-gnu
+    = help: try adding a `where` bound using this expression: `where [(); { N + 1 }]:`
9 error: unconstrained generic constant
10   --> $DIR/generic-expr-default.rs:14:58



The actual stderr differed from the expected stderr.
Actual stderr saved to /checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/const-generics/defaults/generic-expr-default/generic-expr-default.stderr
To update references, rerun the tests and pass the `--bless` flag
To only update this specific test, also pass `--test-args const-generics/defaults/generic-expr-default.rs`

error: 1 errors occurred comparing output.
status: exit status: 1
command: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/src/test/ui/const-generics/defaults/generic-expr-default.rs" "-Zthreads=1" "--target=i686-unknown-linux-gnu" "--error-format" "json" "--json" "future-incompat" "-Ccodegen-units=1" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/const-generics/defaults/generic-expr-default" "-A" "unused" "-Crpath" "-O" "-Cdebuginfo=0" "-Lnative=/checkout/obj/build/i686-unknown-linux-gnu/native/rust-test-helpers" "-Clinker=cc" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/const-generics/defaults/generic-expr-default/auxiliary"
------------------------------------------

------------------------------------------
stderr:
stderr:
------------------------------------------
error: unconstrained generic constant
  --> /checkout/src/test/ui/const-generics/defaults/generic-expr-default.rs:5:54
   |
LL | pub fn needs_evaluatable_bound<const N1: usize>() -> Foo<N1> {
   |
   |
   = help: try adding a `where` bound using this expression: `where [(); { N + 1 }]:`
error: unconstrained generic constant
  --> /checkout/src/test/ui/const-generics/defaults/generic-expr-default.rs:14:58
   |
   |
LL | fn needs_evaluatable_bound_alias<T, const N: usize>() -> FooAlias<N>
   |
   |
   = help: try adding a `where` bound using this expression: `where [(); { N + 1 }]:`
error: aborting due to 2 previous errors


------------------------------------------
------------------------------------------


---- [ui] ui/const-generics/generic_const_exprs/array-size-in-generic-struct-param.rs#full stdout ----
diff of stderr:

4 LL | struct ArithArrayLen<const N: usize>([u32; 0 + N]);
6    |
6    |
-    = help: try adding a `where` bound using this expression: `where [(); { 0 + N }]:`
+    = help: try adding a `where` bound using this expression: `where [(); 0 + N]:`
9 error: overly complex generic constant
10   --> $DIR/array-size-in-generic-struct-param.rs:19:15



The actual stderr differed from the expected stderr.
Actual stderr saved to /checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/const-generics/generic_const_exprs/array-size-in-generic-struct-param.full/array-size-in-generic-struct-param.full.stderr
To only update this specific test, also pass `--test-args const-generics/generic_const_exprs/array-size-in-generic-struct-param.rs`


error in revision `full`: 1 errors occurred comparing output.
status: exit status: 1
command: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/src/test/ui/const-generics/generic_const_exprs/array-size-in-generic-struct-param.rs" "-Zthreads=1" "--target=i686-unknown-linux-gnu" "--cfg" "full" "--error-format" "json" "--json" "future-incompat" "-Ccodegen-units=1" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/const-generics/generic_const_exprs/array-size-in-generic-struct-param.full" "-A" "unused" "-Crpath" "-O" "-Cdebuginfo=0" "-Lnative=/checkout/obj/build/i686-unknown-linux-gnu/native/rust-test-helpers" "-Clinker=cc" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/const-generics/generic_const_exprs/array-size-in-generic-struct-param.full/auxiliary"
------------------------------------------

------------------------------------------
stderr:
stderr:
------------------------------------------
error: unconstrained generic constant
  --> /checkout/src/test/ui/const-generics/generic_const_exprs/array-size-in-generic-struct-param.rs:8:38
   |
LL | struct ArithArrayLen<const N: usize>([u32; 0 + N]);
   |
   |
   = help: try adding a `where` bound using this expression: `where [(); 0 + N]:`
error: overly complex generic constant
  --> /checkout/src/test/ui/const-generics/generic_const_exprs/array-size-in-generic-struct-param.rs:19:15
   |
   |
LL |     arr: [u8; CFG.arr_size],
   |               ^^^^^^^^^^^^ field access is not supported in generic constant
   |
   = help: consider moving this anonymous constant into a `const` function

error: aborting due to 2 previous errors



------------------------------------------


---- [ui] ui/const-generics/mismatched-const-errors.rs stdout ----
diff of stderr:

4 LL | fn foo1<const N: usize>() -> HasTrait<HasCastInTraitImpl<{ N + 2}, { N }>> {
6    |
6    |
-    = help: try adding a `where` bound using this expression: `where [(); { N + 2 + 1 }]:`
+    = help: try adding a `where` bound using this expression: `where [(); { M + 1 }]:`
8 note: required because of the requirements on the impl of `Trait` for `HasCastInTraitImpl<{ N + 2}, N>`
10    |

20   --> $DIR/mismatched-const-errors.rs:9:30
21    |
21    |
22 LL | fn foo1<const N: usize>() -> HasTrait<HasCastInTraitImpl<{ N + 2}, { N }>> {
-    |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `N`, found `{ N + 2 + 1 }`
+    |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `N`, found `{ M + 1 }`
25    = note: expected type `N`
25    = note: expected type `N`
-               found type `{ N + 2 + 1 }`
+               found type `{ M + 1 }`
28 error: unconstrained generic constant
29   --> $DIR/mismatched-const-errors.rs:15:30


31 LL | fn foo2<const N: usize>() -> HasTrait<HasCastInTraitImpl<{ N + 1}, { N + 1 }>> {
33    |
33    |
-    = help: try adding a `where` bound using this expression: `where [(); { N + 1 + 1 }]:`
+    = help: try adding a `where` bound using this expression: `where [(); { M + 1 }]:`
35 note: required because of the requirements on the impl of `Trait` for `HasCastInTraitImpl<{ N + 1}, { N + 1 }>`
37    |

47   --> $DIR/mismatched-const-errors.rs:15:30
48    |
48    |
49 LL | fn foo2<const N: usize>() -> HasTrait<HasCastInTraitImpl<{ N + 1}, { N + 1 }>> {
-    |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `{ N + 1 }`, found `{ N + 1 + 1 }`
+    |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `{ N + 1 }`, found `{ M + 1 }`
51    |
52    = note: expected type `{ N + 1 }`
-               found type `{ N + 1 + 1 }`
+               found type `{ M + 1 }`
55 error: unconstrained generic constant
56   --> $DIR/mismatched-const-errors.rs:21:30


58 LL | fn foo3<const N: usize>() -> HasTrait<HasCastInTraitImpl<{ N + 1}, { N - 1}>> {
60    |
60    |
-    = help: try adding a `where` bound using this expression: `where [(); { N + 1 + 1 }]:`
+    = help: try adding a `where` bound using this expression: `where [(); { M + 1 }]:`
62 note: required because of the requirements on the impl of `Trait` for `HasCastInTraitImpl<{ N + 1}, { N - 1}>`
64    |

74   --> $DIR/mismatched-const-errors.rs:21:30
75    |
75    |
76 LL | fn foo3<const N: usize>() -> HasTrait<HasCastInTraitImpl<{ N + 1}, { N - 1}>> {
-    |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `{ N - 1}`, found `{ N + 1 + 1 }`
+    |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `{ N - 1}`, found `{ M + 1 }`
78    |
79    = note: expected type `{ N - 1}`
-               found type `{ N + 1 + 1 }`
+               found type `{ M + 1 }`
82 error: unconstrained generic constant
83   --> $DIR/mismatched-const-errors.rs:27:44


85 LL | fn foo4<const N: usize>(c : [usize; N]) -> HasTrait<HasCastInTraitImpl<{ N - 1}, { N }>> {
87    |
87    |
-    = help: try adding a `where` bound using this expression: `where [(); { N - 1 + 1 }]:`
+    = help: try adding a `where` bound using this expression: `where [(); { M + 1 }]:`
89 note: required because of the requirements on the impl of `Trait` for `HasCastInTraitImpl<{ N - 1}, N>`
91    |

101   --> $DIR/mismatched-const-errors.rs:27:44
102    |
102    |
103 LL | fn foo4<const N: usize>(c : [usize; N]) -> HasTrait<HasCastInTraitImpl<{ N - 1}, { N }>> {
-    |                                            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `N`, found `{ N - 1 + 1 }`
+    |                                            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `N`, found `{ M + 1 }`
106    = note: expected type `N`
106    = note: expected type `N`
-               found type `{ N - 1 + 1 }`
+               found type `{ M + 1 }`
109 error: unconstrained generic constant
110   --> $DIR/mismatched-const-errors.rs:33:30


112 LL | fn foo5<const N: usize>() -> HasTrait<HasCastInTraitImpl<{ N + N }, { 2 * N }>> {
114    |
114    |
-    = help: try adding a `where` bound using this expression: `where [(); { N + N + 1 }]:`
+    = help: try adding a `where` bound using this expression: `where [(); { M + 1 }]:`
116 note: required because of the requirements on the impl of `Trait` for `HasCastInTraitImpl<{ N + N }, { 2 * N }>`
118    |

128   --> $DIR/mismatched-const-errors.rs:33:30
129    |
129    |
130 LL | fn foo5<const N: usize>() -> HasTrait<HasCastInTraitImpl<{ N + N }, { 2 * N }>> {
-    |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `{ 2 * N }`, found `{ N + N + 1 }`
+    |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `{ 2 * N }`, found `{ M + 1 }`
132    |
133    = note: expected type `{ 2 * N }`
-               found type `{ N + N + 1 }`
+               found type `{ M + 1 }`
136 error: aborting due to 10 previous errors
137 



The actual stderr differed from the expected stderr.
Actual stderr saved to /checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/const-generics/mismatched-const-errors/mismatched-const-errors.stderr
To update references, rerun the tests and pass the `--bless` flag
To only update this specific test, also pass `--test-args const-generics/mismatched-const-errors.rs`

error: 1 errors occurred comparing output.
status: exit status: 1
command: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/src/test/ui/const-generics/mismatched-const-errors.rs" "-Zthreads=1" "--target=i686-unknown-linux-gnu" "--error-format" "json" "--json" "future-incompat" "-Ccodegen-units=1" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/const-generics/mismatched-const-errors" "-A" "unused" "-Crpath" "-O" "-Cdebuginfo=0" "-Lnative=/checkout/obj/build/i686-unknown-linux-gnu/native/rust-test-helpers" "-Clinker=cc" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/const-generics/mismatched-const-errors/auxiliary"
------------------------------------------

------------------------------------------
stderr:
stderr:
------------------------------------------
error: unconstrained generic constant
  --> /checkout/src/test/ui/const-generics/mismatched-const-errors.rs:9:30
   |
LL | fn foo1<const N: usize>() -> HasTrait<HasCastInTraitImpl<{ N + 2}, { N }>> {
   |
   |
   = help: try adding a `where` bound using this expression: `where [(); { M + 1 }]:`
note: required because of the requirements on the impl of `Trait` for `HasCastInTraitImpl<{ N + 2}, N>`
   |
   |
LL | impl<const M: usize> Trait for HasCastInTraitImpl<M, { M + 1 }> {}
   |                      ^^^^^     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
note: required by a bound in `HasTrait`
   |
   |
LL | pub struct HasTrait<T: Trait>(T);
   |                        ^^^^^ required by this bound in `HasTrait`
error[E0308]: mismatched types
  --> /checkout/src/test/ui/const-generics/mismatched-const-errors.rs:9:30
   |
   |
LL | fn foo1<const N: usize>() -> HasTrait<HasCastInTraitImpl<{ N + 2}, { N }>> {
   |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `N`, found `{ M + 1 }`
   = note: expected type `N`
   = note: expected type `N`
              found type `{ M + 1 }`
error: unconstrained generic constant
  --> /checkout/src/test/ui/const-generics/mismatched-const-errors.rs:15:30
   |
   |
LL | fn foo2<const N: usize>() -> HasTrait<HasCastInTraitImpl<{ N + 1}, { N + 1 }>> {
   |
   |
   = help: try adding a `where` bound using this expression: `where [(); { M + 1 }]:`
note: required because of the requirements on the impl of `Trait` for `HasCastInTraitImpl<{ N + 1}, { N + 1 }>`
   |
   |
LL | impl<const M: usize> Trait for HasCastInTraitImpl<M, { M + 1 }> {}
   |                      ^^^^^     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
note: required by a bound in `HasTrait`
   |
   |
LL | pub struct HasTrait<T: Trait>(T);
   |                        ^^^^^ required by this bound in `HasTrait`
error[E0308]: mismatched types
  --> /checkout/src/test/ui/const-generics/mismatched-const-errors.rs:15:30
   |
   |
LL | fn foo2<const N: usize>() -> HasTrait<HasCastInTraitImpl<{ N + 1}, { N + 1 }>> {
   |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `{ N + 1 }`, found `{ M + 1 }`
   |
   = note: expected type `{ N + 1 }`
              found type `{ M + 1 }`
error: unconstrained generic constant
  --> /checkout/src/test/ui/const-generics/mismatched-const-errors.rs:21:30
   |
   |
LL | fn foo3<const N: usize>() -> HasTrait<HasCastInTraitImpl<{ N + 1}, { N - 1}>> {
   |
   |
   = help: try adding a `where` bound using this expression: `where [(); { M + 1 }]:`
note: required because of the requirements on the impl of `Trait` for `HasCastInTraitImpl<{ N + 1}, { N - 1}>`
   |
   |
LL | impl<const M: usize> Trait for HasCastInTraitImpl<M, { M + 1 }> {}
   |                      ^^^^^     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
note: required by a bound in `HasTrait`
   |
   |
LL | pub struct HasTrait<T: Trait>(T);
   |                        ^^^^^ required by this bound in `HasTrait`
error[E0308]: mismatched types
  --> /checkout/src/test/ui/const-generics/mismatched-const-errors.rs:21:30
   |
   |
LL | fn foo3<const N: usize>() -> HasTrait<HasCastInTraitImpl<{ N + 1}, { N - 1}>> {
   |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `{ N - 1}`, found `{ M + 1 }`
   |
   = note: expected type `{ N - 1}`
              found type `{ M + 1 }`
error: unconstrained generic constant
  --> /checkout/src/test/ui/const-generics/mismatched-const-errors.rs:27:44
   |
   |
LL | fn foo4<const N: usize>(c : [usize; N]) -> HasTrait<HasCastInTraitImpl<{ N - 1}, { N }>> {
   |
   |
   = help: try adding a `where` bound using this expression: `where [(); { M + 1 }]:`
note: required because of the requirements on the impl of `Trait` for `HasCastInTraitImpl<{ N - 1}, N>`
   |
   |
LL | impl<const M: usize> Trait for HasCastInTraitImpl<M, { M + 1 }> {}
   |                      ^^^^^     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
note: required by a bound in `HasTrait`
   |
   |
LL | pub struct HasTrait<T: Trait>(T);
   |                        ^^^^^ required by this bound in `HasTrait`
error[E0308]: mismatched types
  --> /checkout/src/test/ui/const-generics/mismatched-const-errors.rs:27:44
   |
   |
LL | fn foo4<const N: usize>(c : [usize; N]) -> HasTrait<HasCastInTraitImpl<{ N - 1}, { N }>> {
   |                                            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `N`, found `{ M + 1 }`
   = note: expected type `N`
   = note: expected type `N`
              found type `{ M + 1 }`
error: unconstrained generic constant
  --> /checkout/src/test/ui/const-generics/mismatched-const-errors.rs:33:30
   |
   |
LL | fn foo5<const N: usize>() -> HasTrait<HasCastInTraitImpl<{ N + N }, { 2 * N }>> {
   |
   |
   = help: try adding a `where` bound using this expression: `where [(); { M + 1 }]:`
note: required because of the requirements on the impl of `Trait` for `HasCastInTraitImpl<{ N + N }, { 2 * N }>`
   |
   |
LL | impl<const M: usize> Trait for HasCastInTraitImpl<M, { M + 1 }> {}
   |                      ^^^^^     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
note: required by a bound in `HasTrait`
   |
   |
LL | pub struct HasTrait<T: Trait>(T);
   |                        ^^^^^ required by this bound in `HasTrait`
error[E0308]: mismatched types
  --> /checkout/src/test/ui/const-generics/mismatched-const-errors.rs:33:30
   |
   |
LL | fn foo5<const N: usize>() -> HasTrait<HasCastInTraitImpl<{ N + N }, { 2 * N }>> {
   |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `{ 2 * N }`, found `{ M + 1 }`
   |
   = note: expected type `{ 2 * N }`
              found type `{ M + 1 }`
error: aborting due to 10 previous errors

For more information about this error, try `rustc --explain E0308`.


------------------------------------------


---- [ui] ui/const-generics/mismatched-const-types-precedence.rs stdout ----
diff of stderr:

4 LL |   let _: [u32; 3 * 2 + N + K] = foo::<{ 2 + N }, K>(a, b);
6    |
6    |
-    = help: try adding a `where` bound using this expression: `where [(); { 3 * { 2 + N + K } }]:`
+    = help: try adding a `where` bound using this expression: `where [(); 3 * {M + K}]:`
8 note: required by a bound in `foo`
10    |


17 LL |   let _: [u32; 3 * 2 + N + K] = foo::<{ 2 + N }, K>(a, b);
19    |
19    |
-    = help: try adding a `where` bound using this expression: `where [(); { 3 * 2 + N + K }]:`
+    = help: try adding a `where` bound using this expression: `where [(); 3 * 2 + N + K]:`
22 error[E0308]: mismatched types
23   --> $DIR/mismatched-const-types-precedence.rs:6:33

24    |
24    |
25 LL |   let _: [u32; 3 * 2 + N + K] = foo::<{ 2 + N }, K>(a, b);
-    |                                 ^^^^^^^^^^^^^^^^^^^^^^^^^ expected `3 * 2 + N + K`, found `{ 3 * { 2 + N + K } }`
+    |                                 ^^^^^^^^^^^^^^^^^^^^^^^^^ expected `3 * 2 + N + K`, found `3 * {M + K}`
27    |
28    = note: expected type `3 * 2 + N + K`
-               found type `{ 3 * { 2 + N + K } }`
+               found type `3 * {M + K}`
31 error: unconstrained generic constant
32   --> $DIR/mismatched-const-types-precedence.rs:6:33


34 LL |   let _: [u32; 3 * 2 + N + K] = foo::<{ 2 + N }, K>(a, b);
36    |
36    |
-    = help: try adding a `where` bound using this expression: `where [(); { 3 * { 2 + N + K } }]:`
+    = help: try adding a `where` bound using this expression: `where [(); 3 * {M + K}]:`
38 note: required by a bound in `foo`
40    |


55 LL |   let _: [u32; 3 * 2 + N * K] = foo2::<{ 2 + N }, K>(a, b);
57    |
57    |
-    = help: try adding a `where` bound using this expression: `where [(); { 3 * { 2 + N } * K }]:`
+    = help: try adding a `where` bound using this expression: `where [(); 3 * M * K]:`
59 note: required by a bound in `foo2`
61    |


68 LL |   let _: [u32; 3 * 2 + N * K] = foo2::<{ 2 + N }, K>(a, b);
70    |
70    |
-    = help: try adding a `where` bound using this expression: `where [(); { 3 * 2 + N * K }]:`
+    = help: try adding a `where` bound using this expression: `where [(); 3 * 2 + N * K]:`
73 error[E0308]: mismatched types
74   --> $DIR/mismatched-const-types-precedence.rs:18:33

75    |
75    |
76 LL |   let _: [u32; 3 * 2 + N * K] = foo2::<{ 2 + N }, K>(a, b);
-    |                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `3 * 2 + N * K`, found `{ 3 * { 2 + N } * K }`
+    |                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `3 * 2 + N * K`, found `3 * M * K`
78    |
79    = note: expected type `3 * 2 + N * K`
-               found type `{ 3 * { 2 + N } * K }`
+               found type `3 * M * K`
82 error: unconstrained generic constant
83   --> $DIR/mismatched-const-types-precedence.rs:18:33


85 LL |   let _: [u32; 3 * 2 + N * K] = foo2::<{ 2 + N }, K>(a, b);
87    |
87    |
-    = help: try adding a `where` bound using this expression: `where [(); { 3 * { 2 + N } * K }]:`
+    = help: try adding a `where` bound using this expression: `where [(); 3 * M * K]:`
89 note: required by a bound in `foo2`
91    |


106 LL |   let _: [u32; 3 * 2 + N * K + L] = foo3::<{ 2 + N }, K, L>(a, b);
108    |
108    |
-    = help: try adding a `where` bound using this expression: `where [(); { 3 * { 2 + N } * K + L }]:`
+    = help: try adding a `where` bound using this expression: `where [(); 3 * M * {K + L}]:`
110 note: required by a bound in `foo3`
112    |


121 LL |   let _: [u32; 3 * 2 + N * K + L] = foo3::<{ 2 + N }, K, L>(a, b);
123    |
123    |
-    = help: try adding a `where` bound using this expression: `where [(); { 3 * 2 + N * K + L }]:`
+    = help: try adding a `where` bound using this expression: `where [(); 3 * 2 + N * K + L]:`
126 error[E0308]: mismatched types
127   --> $DIR/mismatched-const-types-precedence.rs:30:37

128    |
128    |
129 LL |   let _: [u32; 3 * 2 + N * K + L] = foo3::<{ 2 + N }, K, L>(a, b);
-    |                                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `3 * 2 + N * K + L`, found `{ 3 * { 2 + N } * K + L }`
+    |                                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `3 * 2 + N * K + L`, found `3 * M * {K + L}`
131    |
132    = note: expected type `3 * 2 + N * K + L`
-               found type `{ 3 * { 2 + N } * K + L }`
+               found type `3 * M * {K + L}`
135 error: unconstrained generic constant
136   --> $DIR/mismatched-const-types-precedence.rs:30:37


138 LL |   let _: [u32; 3 * 2 + N * K + L] = foo3::<{ 2 + N }, K, L>(a, b);
140    |
140    |
-    = help: try adding a `where` bound using this expression: `where [(); { 3 * { 2 + N } * K + L }]:`
+    = help: try adding a `where` bound using this expression: `where [(); 3 * M * {K + L}]:`
142 note: required by a bound in `foo3`
144    |


The actual stderr differed from the expected stderr.
The actual stderr differed from the expected stderr.
Actual stderr saved to /checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/const-generics/mismatched-const-types-precedence/mismatched-const-types-precedence.stderr
To update references, rerun the tests and pass the `--bless` flag
To only update this specific test, also pass `--test-args const-generics/mismatched-const-types-precedence.rs`

error: 1 errors occurred comparing output.
status: exit status: 1
command: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/src/test/ui/const-generics/mismatched-const-types-precedence.rs" "-Zthreads=1" "--target=i686-unknown-linux-gnu" "--error-format" "json" "--json" "future-incompat" "-Ccodegen-units=1" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/const-generics/mismatched-const-types-precedence" "-A" "unused" "-Crpath" "-O" "-Cdebuginfo=0" "-Lnative=/checkout/obj/build/i686-unknown-linux-gnu/native/rust-test-helpers" "-Clinker=cc" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/const-generics/mismatched-const-types-precedence/auxiliary"
---
test result: FAILED. 12345 passed; 4 failed; 173 ignored; 0 measured; 0 filtered out; finished in 106.82s



command did not execute successfully: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0-tools-bin/compiletest" "--compile-lib-path" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib" "--run-lib-path" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/i686-unknown-linux-gnu/lib" "--rustc-path" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "--src-base" "/checkout/src/test/ui" "--build-base" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui" "--stage-id" "stage2-i686-unknown-linux-gnu" "--suite" "ui" "--mode" "ui" "--target" "i686-unknown-linux-gnu" "--host" "x86_64-unknown-linux-gnu" "--llvm-filecheck" "/usr/lib/llvm-12/bin/FileCheck" "--pass" "check" "--nodejs" "/usr/bin/node" "--linker" "cc" "--host-rustcflags" "-Crpath -O -Cdebuginfo=0  -Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "--target-rustcflags" "-Crpath -O -Cdebuginfo=0  -Lnative=/checkout/obj/build/i686-unknown-linux-gnu/native/rust-test-helpers" "--docck-python" "/usr/bin/python3" "--lldb-python" "/usr/bin/python3" "--gdb" "/usr/bin/gdb" "--quiet" "--llvm-version" "12.0.0" "--llvm-components" "aarch64 aarch64asmparser aarch64codegen aarch64desc aarch64disassembler aarch64info aarch64utils aggressiveinstcombine all all-targets amdgpu amdgpuasmparser amdgpucodegen amdgpudesc amdgpudisassembler amdgpuinfo amdgpuutils analysis arm armasmparser armcodegen armdesc armdisassembler arminfo armutils asmparser asmprinter avr avrasmparser avrcodegen avrdesc avrdisassembler avrinfo binaryformat bitreader bitstreamreader bitwriter bpf bpfasmparser bpfcodegen bpfdesc bpfdisassembler bpfinfo cfguard codegen core coroutines coverage debuginfocodeview debuginfodwarf debuginfogsym debuginfomsf debuginfopdb demangle dlltooldriver dwarflinker engine executionengine extensions filecheck frontendopenacc frontendopenmp fuzzmutate globalisel hellonew hexagon hexagonasmparser hexagoncodegen hexagondesc hexagondisassembler hexagoninfo instcombine instrumentation interfacestub interpreter ipo irreader jitlink lanai lanaiasmparser lanaicodegen lanaidesc lanaidisassembler lanaiinfo libdriver lineeditor linker lto mc mca mcdisassembler mcjit mcparser mips mipsasmparser mipscodegen mipsdesc mipsdisassembler mipsinfo mirparser msp430 msp430asmparser msp430codegen msp430desc msp430disassembler msp430info native nativecodegen nvptx nvptxcodegen nvptxdesc nvptxinfo objcarcopts object objectyaml option orcjit orcshared orctargetprocess passes perfjitevents powerpc powerpcasmparser powerpccodegen powerpcdesc powerpcdisassembler powerpcinfo profiledata remarks riscv riscvasmparser riscvcodegen riscvdesc riscvdisassembler riscvinfo runtimedyld scalaropts selectiondag sparc sparcasmparser sparccodegen sparcdesc sparcdisassembler sparcinfo support symbolize systemz systemzasmparser systemzcodegen systemzdesc systemzdisassembler systemzinfo tablegen target textapi transformutils vectorize webassembly webassemblyasmparser webassemblycodegen webassemblydesc webassemblydisassembler webassemblyinfo windowsmanifest x86 x86asmparser x86codegen x86desc x86disassembler x86info xcore xcorecodegen xcoredesc xcoredisassembler xcoreinfo xray" "--cc" "" "--cxx" "" "--cflags" "" "--adb-path" "adb" "--adb-test-dir" "/data/tmp/work" "--android-cross-path" "" "--channel" "nightly" "--color" "always"


Build completed unsuccessfully in 0:01:49

bors · 2022-01-04T23:10:12Z

☔ The latest upstream changes (presumably #92556) made this pull request unmergeable. Please resolve the merge conflicts.

JohnCSimon · 2022-01-23T01:17:56Z

Ping from triage:
@b-naber can you post your status on this PR? It has sat idle for almost a month.

b-naber · 2022-01-24T16:39:11Z

@BoxyUwU Any ideas why try_to_string doesn't work in light of what you said about the origin of the CI failures? ~~I also find it weird that CI passed prior to the 'implement precedence for anon const mismatch' commit even though `to_i64' was used in the 'allow AbstractConsts to be printed' commit already~~ (Actually it looks as if CI never passed). And there isn't any other existing function to print Scalars in non-hex representation.

BoxyUwU · 2022-01-26T20:51:12Z

Not sure why your code isnt working but I looked around a bit and I think PrettyPrinter::pretty_print_const_scalar can be used to get it printed properly.

JohnCSimon · 2022-03-20T05:21:09Z

@b-naber
Ping from triage: I'm closing this due to inactivity, Please reopen when you are ready to continue with this. Thanks for your contribution.

@rustbot label: +S-inactive

rust-highfive assigned jackh726 Nov 17, 2021

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b-naber force-pushed the const-type-mismatch-diagnostics branch from d7d3787 to 978b853 Compare November 17, 2021 20:06

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apiraino added the T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. label Nov 18, 2021

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BoxyUwU reviewed Dec 21, 2021

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b-naber added 10 commits December 24, 2021 15:20

introduce new TypeError variant: ConstMismatchTooGeneric

9e75cbe

make BinOp and UnOp 'displayable'

2569e59

allow AbstractConsts to be printed for diagnostics

7bf3dc1

create suggestions for mismatched consts

4bcd67c

try to create suggestions for mismatched consts in FulfillmentError::…

3b92583

…TooGeneric cases

add tests

3c9701b

suggest correct anonymous constant in where bounds in NonConstEvaluat…

e1b1b2f

…able error message

bless tests

bf67758

implement precedence for anon const mismatch suggestions

bb8be4f

add tests for precedence

a262e3e

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b-naber force-pushed the const-type-mismatch-diagnostics branch from 57d137e to 6ed9dfd Compare December 28, 2021 09:18

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properly convert scalar to string

7b72ba8

b-naber force-pushed the const-type-mismatch-diagnostics branch from 6ed9dfd to 7b72ba8 Compare December 28, 2021 11:08

JohnCSimon added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Feb 13, 2022

JohnCSimon closed this Mar 20, 2022

rustbot added the S-inactive Status: Inactive and waiting on the author. This is often applied to closed PRs. label Mar 20, 2022

lcnr mentioned this pull request Jun 24, 2022

unsatisfied trait bound uses _ for unevaluated constants #82934

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Improve errors on const mismatches #90987

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Improve errors on const mismatches #90987

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