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Rollup merge of #74934 - nbdd0121:issue-73976, r=ecstatic-morse 

Improve diagnostics when constant pattern is too generic

This PR is a follow-up to PR #74538 and issue #73976

When constants queries Layout, TypeId or type_name of a generic parameter, instead of emitting `could not evaluate constant pattern`, we will instead emit a more detailed message `constant pattern depends on a generic parameter`.
This commit is contained in:
Manish Goregaokar 2020-07-30 13:04:42 -07:00 committed by GitHub
parent 0a45b1303c 4e963d58c7
commit b0d426165f
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GPG Key ID: 4AEE18F83AFDEB23
3 changed files with 15 additions and 9 deletions
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8
src/librustc_mir_build/hair/pattern/mod.rs
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@ -16,7 +16,7 @@ use rustc_hir::pat_util::EnumerateAndAdjustIterator;
use rustc_hir::RangeEnd;
use rustc_index::vec::Idx;
use rustc_middle::mir::interpret::{get_slice_bytes, sign_extend, ConstValue};
use rustc_middle::mir::interpret::{LitToConstError, LitToConstInput};
use rustc_middle::mir::interpret::{ErrorHandled, LitToConstError, LitToConstInput};
use rustc_middle::mir::UserTypeProjection;
use rustc_middle::mir::{BorrowKind, Field, Mutability};
use rustc_middle::ty::subst::{GenericArg, SubstsRef};
@ -834,6 +834,12 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
pattern
}
}
Err(ErrorHandled::TooGeneric) => {
// While `Reported | Linted` cases will have diagnostics emitted already
// it is not true for TooGeneric case, so we need to give user more information.
self.tcx.sess.span_err(span, "constant pattern depends on a generic parameter");
pat_from_kind(PatKind::Wild)
}
Err(_) => {
self.tcx.sess.span_err(span, "could not evaluate constant pattern");
pat_from_kind(PatKind::Wild)

8
src/test/ui/consts/issue-73976-polymorphic.rs
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@ -17,8 +17,8 @@ impl<T: 'static> GetTypeId<T> {
const fn check_type_id<T: 'static>() -> bool {
matches!(GetTypeId::<T>::VALUE, GetTypeId::<T>::VALUE)
//~^ ERROR could not evaluate constant pattern
//~| ERROR could not evaluate constant pattern
//~^ ERROR constant pattern depends on a generic parameter
//~| ERROR constant pattern depends on a generic parameter
}
pub struct GetTypeNameLen<T>(T);
@ -29,8 +29,8 @@ impl<T: 'static> GetTypeNameLen<T> {
const fn check_type_name_len<T: 'static>() -> bool {
matches!(GetTypeNameLen::<T>::VALUE, GetTypeNameLen::<T>::VALUE)
//~^ ERROR could not evaluate constant pattern
//~| ERROR could not evaluate constant pattern
//~^ ERROR constant pattern depends on a generic parameter
//~| ERROR constant pattern depends on a generic parameter
}
fn main() {

8
src/test/ui/consts/issue-73976-polymorphic.stderr
View File

@ -1,22 +1,22 @@
error: could not evaluate constant pattern
error: constant pattern depends on a generic parameter
--> $DIR/issue-73976-polymorphic.rs:19:37
|
LL | matches!(GetTypeId::<T>::VALUE, GetTypeId::<T>::VALUE)
| ^^^^^^^^^^^^^^^^^^^^^
error: could not evaluate constant pattern
error: constant pattern depends on a generic parameter
--> $DIR/issue-73976-polymorphic.rs:31:42
|
LL | matches!(GetTypeNameLen::<T>::VALUE, GetTypeNameLen::<T>::VALUE)
| ^^^^^^^^^^^^^^^^^^^^^^^^^^
error: could not evaluate constant pattern
error: constant pattern depends on a generic parameter
--> $DIR/issue-73976-polymorphic.rs:19:37
|
LL | matches!(GetTypeId::<T>::VALUE, GetTypeId::<T>::VALUE)
| ^^^^^^^^^^^^^^^^^^^^^
error: could not evaluate constant pattern
error: constant pattern depends on a generic parameter
--> $DIR/issue-73976-polymorphic.rs:31:42
|
LL | matches!(GetTypeNameLen::<T>::VALUE, GetTypeNameLen::<T>::VALUE)