rust-lang/rust
1
0
Fork 0
Code Issues Pull Requests Actions 1 Packages Projects Releases Wiki Activity

Rollup merge of #120556 - fmease:improve-unused-generic-param-diags, r=oli-obk

Browse Source 
Improve the diagnostics for unused generic parameters

* Don't emit two errors (namely E0091 *and* E0392) for unused type parameters on *lazy* type aliases
* Fix the diagnostic help message of E0392 for *lazy* type aliases: Don't talk about the “fields” of lazy type aliases (use the term “body” instead) and don't suggest `PhantomData` for them, it doesn't make much sense
* Consolidate the diagnostics for E0091 (unused type parameters in type aliases) and E0392 (unused generic parameters due to bivariance) and make it translatable
  * Still keep the error codes distinct (for now)
  * Naturally leads to better diagnostics for E0091

r? ```@oli-obk``` (to ballast your review load :P) or compiler
This commit is contained in:
Matthias Krüger
2024-02-04 19:42:12 +01:00
committed by GitHub
parent 1547510dc6 02320b502d
commit 7fa99bfb71
43 changed files with 370 additions and 170 deletions
Download Patch File Download Diff File Expand all files Collapse all files

62
compiler/rustc_hir_analysis/src/check/wfcheck.rs
View File

@@ -1,11 +1,10 @@
use crate::autoderef::Autoderef;
use crate::constrained_generic_params::{identify_constrained_generic_params, Parameter};
use crate::errors;
use rustc_ast as ast;
use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexSet};
use rustc_errors::{
codes::*, pluralize, struct_span_code_err, Applicability, DiagnosticBuilder, ErrorGuaranteed,
};
use rustc_errors::{codes::*, pluralize, struct_span_code_err, Applicability, ErrorGuaranteed};
use rustc_hir as hir;
use rustc_hir::def_id::{DefId, LocalDefId, LocalModDefId};
use rustc_hir::lang_items::LangItem;
@@ -21,7 +20,7 @@ use rustc_middle::ty::{
};
use rustc_middle::ty::{GenericArgKind, GenericArgs};
use rustc_session::parse::feature_err;
use rustc_span::symbol::{sym, Ident, Symbol};
use rustc_span::symbol::{sym, Ident};
use rustc_span::{Span, DUMMY_SP};
use rustc_target::spec::abi::Abi;
use rustc_trait_selection::regions::InferCtxtRegionExt;
@@ -1869,7 +1868,7 @@ fn check_variances_for_type_defn<'tcx>(
hir::ParamName::Error => {}
_ => {
let has_explicit_bounds = explicitly_bounded_params.contains(&parameter);
report_bivariance(tcx, hir_param, has_explicit_bounds);
report_bivariance(tcx, hir_param, has_explicit_bounds, item.kind);
}
}
}
@@ -1879,30 +1878,38 @@ fn report_bivariance(
tcx: TyCtxt<'_>,
param: &rustc_hir::GenericParam<'_>,
has_explicit_bounds: bool,
item_kind: ItemKind<'_>,
) -> ErrorGuaranteed {
let span = param.span;
let param_name = param.name.ident().name;
let mut err = error_392(tcx, span, param_name);
let param_name = param.name.ident();
let suggested_marker_id = tcx.lang_items().phantom_data();
// Help is available only in presence of lang items.
let msg = if let Some(def_id) = suggested_marker_id {
format!(
"consider removing `{}`, referring to it in a field, or using a marker such as `{}`",
param_name,
tcx.def_path_str(def_id),
)
} else {
format!("consider removing `{param_name}` or referring to it in a field")
let help = match item_kind {
ItemKind::Enum(..) | ItemKind::Struct(..) | ItemKind::Union(..) => {
if let Some(def_id) = tcx.lang_items().phantom_data() {
errors::UnusedGenericParameterHelp::Adt {
param_name,
phantom_data: tcx.def_path_str(def_id),
}
} else {
errors::UnusedGenericParameterHelp::AdtNoPhantomData { param_name }
}
}
ItemKind::TyAlias(..) => errors::UnusedGenericParameterHelp::TyAlias { param_name },
item_kind => bug!("report_bivariance: unexpected item kind: {item_kind:?}"),
};
err.help(msg);
if matches!(param.kind, hir::GenericParamKind::Type { .. }) && !has_explicit_bounds {
err.help(format!(
"if you intended `{param_name}` to be a const parameter, use `const {param_name}: usize` instead"
));
}
err.emit()
let const_param_help =
matches!(param.kind, hir::GenericParamKind::Type { .. } if !has_explicit_bounds)
.then_some(());
let mut diag = tcx.dcx().create_err(errors::UnusedGenericParameter {
span: param.span,
param_name,
param_def_kind: tcx.def_descr(param.def_id.to_def_id()),
help,
const_param_help,
});
diag.code(E0392);
diag.emit()
}
impl<'tcx> WfCheckingCtxt<'_, 'tcx> {
@@ -1967,11 +1974,6 @@ fn check_mod_type_wf(tcx: TyCtxt<'_>, module: LocalModDefId) -> Result<(), Error
res
}
fn error_392(tcx: TyCtxt<'_>, span: Span, param_name: Symbol) -> DiagnosticBuilder<'_> {
struct_span_code_err!(tcx.dcx(), span, E0392, "parameter `{param_name}` is never used")
.with_span_label(span, "unused parameter")
}
pub fn provide(providers: &mut Providers) {
*providers = Providers { check_mod_type_wf, check_well_formed, ..*providers };
}