Auto merge of rust-lang#142008 - RalfJung:const-eval-error-here, r=oli-obk

const-eval error: always say in which item the error occurred

I don't see why "is this generic" should make a difference. It may be reasonable to key this on whether the error occurs in a `const fn` that was invoked by a const (making it non-obvious which constant it is) vs inside the body of the const.

r? `@oli-obk`

Author: bors

compiler/rustc_const_eval/messages.ftl

@@ -88,11 +88,9 @@ const_eval_division_overflow =
 const_eval_dyn_call_not_a_method =
     `dyn` call trying to call something that is not a method
 
-const_eval_error = {$error_kind ->
-    [static] evaluation of static initializer failed here
-    [const] evaluation of constant value failed here
-    [const_with_path] evaluation of `{$instance}` failed here
-    *[other] {""}
+const_eval_error = evaluation of `{$instance}` failed {$num_frames ->
+    [0] here
+    *[other] inside this call
 }
 
 const_eval_exact_div_has_remainder =

compiler/rustc_const_eval/src/const_eval/eval_queries.rs

@@ -430,27 +430,15 @@ fn report_eval_error<'tcx>(
     let (error, backtrace) = error.into_parts();
     backtrace.print_backtrace();
 
-    let (kind, instance) = if ecx.tcx.is_static(cid.instance.def_id()) {
-        ("static", String::new())
-    } else {
-        // If the current item has generics, we'd like to enrich the message with the
-        // instance and its args: to show the actual compile-time values, in addition to
-        // the expression, leading to the const eval error.
-        let instance = &cid.instance;
-        if !instance.args.is_empty() {
-            let instance = with_no_trimmed_paths!(instance.to_string());
-            ("const_with_path", instance)
-        } else {
-            ("const", String::new())
-        }
-    };
+    let instance = with_no_trimmed_paths!(cid.instance.to_string());
 
     super::report(
         *ecx.tcx,
         error,
         DUMMY_SP,
         || super::get_span_and_frames(ecx.tcx, ecx.stack()),
         |diag, span, frames| {
+            let num_frames = frames.len();
             // FIXME(oli-obk): figure out how to use structured diagnostics again.
             diag.code(E0080);
             diag.span_label(span, crate::fluent_generated::const_eval_error);
@@ -459,7 +447,7 @@ fn report_eval_error<'tcx>(
             }
             // Add after the frame rendering above, as it adds its own `instance` args.
             diag.arg("instance", instance);
-            diag.arg("error_kind", kind);
+            diag.arg("num_frames", num_frames);
         },
     )
 }

src/tools/miri/tests/fail/const-ub-checks.stderr

@@ -2,7 +2,7 @@ error[E0080]: accessing memory based on pointer with alignment ALIGN, but alignm
   --> tests/fail/const-ub-checks.rs:LL:CC
    |
 LL |     ptr.read();
-   |     ^^^^^^^^^^ evaluation of constant value failed here
+   |     ^^^^^^^^^^ evaluation of `UNALIGNED_READ` failed here
 
 note: erroneous constant encountered
   --> tests/fail/const-ub-checks.rs:LL:CC

src/tools/miri/tests/fail/erroneous_const2.stderr

@@ -2,7 +2,7 @@ error[E0080]: attempt to compute `5_u32 - 6_u32`, which would overflow
   --> tests/fail/erroneous_const2.rs:LL:CC
    |
 LL | const FOO: u32 = [X - Y, Y - X][(X < Y) as usize];
-   |                   ^^^^^ evaluation of constant value failed here
+   |                   ^^^^^ evaluation of `FOO` failed here
 
 note: erroneous constant encountered
   --> tests/fail/erroneous_const2.rs:LL:CC

tests/rustdoc-ui/const-evalutation-ice.stderr

@@ -2,7 +2,7 @@ error[E0080]: attempt to compute `0_usize - 1_usize`, which would overflow
   --> $DIR/const-evalutation-ice.rs:10:22
    |
 LL | pub const N: usize = 0 - (mem::size_of::<S>() != 400) as usize;
-   |                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ evaluation of constant value failed here
+   |                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ evaluation of `N` failed here
 
 error: aborting due to 1 previous error
 

tests/ui/array-slice-vec/array_const_index-0.stderr

@@ -2,7 +2,7 @@ error[E0080]: index out of bounds: the length is 0 but the index is 1
   --> $DIR/array_const_index-0.rs:2:16
    |
 LL | const B: i32 = (&A)[1];
-   |                ^^^^^^^ evaluation of constant value failed here
+   |                ^^^^^^^ evaluation of `B` failed here
 
 error: aborting due to 1 previous error
 

tests/ui/array-slice-vec/array_const_index-1.stderr

@@ -2,7 +2,7 @@ error[E0080]: index out of bounds: the length is 0 but the index is 1
   --> $DIR/array_const_index-1.rs:2:16
    |
 LL | const B: i32 = A[1];
-   |                ^^^^ evaluation of constant value failed here
+   |                ^^^^ evaluation of `B` failed here
 
 error: aborting due to 1 previous error
 

tests/ui/borrowck/issue-81899.stderr

@@ -2,7 +2,7 @@ error[E0080]: evaluation panicked: explicit panic
   --> $DIR/issue-81899.rs:6:24
    |
 LL | const _CONST: &[u8] = &f(&[], |_| {});
-   |                        ^^^^^^^^^^^^^^ evaluation of constant value failed here
+   |                        ^^^^^^^^^^^^^^ evaluation of `_CONST` failed inside this call
    |
 note: inside `f::<{closure@$DIR/issue-81899.rs:6:31: 6:34}>`
   --> $DIR/issue-81899.rs:13:5

tests/ui/borrowck/issue-88434-minimal-example.stderr

@@ -2,7 +2,7 @@ error[E0080]: evaluation panicked: explicit panic
   --> $DIR/issue-88434-minimal-example.rs:5:22
    |
 LL | const _CONST: &() = &f(&|_| {});
-   |                      ^^^^^^^^^^ evaluation of constant value failed here
+   |                      ^^^^^^^^^^ evaluation of `_CONST` failed inside this call
    |
 note: inside `f::<{closure@$DIR/issue-88434-minimal-example.rs:5:25: 5:28}>`
   --> $DIR/issue-88434-minimal-example.rs:12:5

tests/ui/borrowck/issue-88434-removal-index-should-be-less.stderr

@@ -2,7 +2,7 @@ error[E0080]: evaluation panicked: explicit panic
   --> $DIR/issue-88434-removal-index-should-be-less.rs:5:24
    |
 LL | const _CONST: &[u8] = &f(&[], |_| {});
-   |                        ^^^^^^^^^^^^^^ evaluation of constant value failed here
+   |                        ^^^^^^^^^^^^^^ evaluation of `_CONST` failed inside this call
    |
 note: inside `f::<{closure@$DIR/issue-88434-removal-index-should-be-less.rs:5:31: 5:34}>`
   --> $DIR/issue-88434-removal-index-should-be-less.rs:12:5