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use crate::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
use crate::infer::InferCtxt;
use crate::traits::{Obligation, ObligationCause, ObligationCtxt};
use rustc_errors::{pluralize, struct_span_err, Applicability, DiagnosticBuilder, ErrorGuaranteed};
use rustc_hir as hir;
use rustc_hir::Node;
use rustc_middle::ty::{self, Ty};
use rustc_span::{Span, DUMMY_SP};
use super::ArgKind;
pub use rustc_infer::traits::error_reporting::*;
pub trait InferCtxtExt<'tcx> {
/// Given some node representing a fn-like thing in the HIR map,
/// returns a span and `ArgKind` information that describes the
/// arguments it expects. This can be supplied to
/// `report_arg_count_mismatch`.
fn get_fn_like_arguments(&self, node: Node<'_>) -> Option<(Span, Option<Span>, Vec<ArgKind>)>;
/// Reports an error when the number of arguments needed by a
/// trait match doesn't match the number that the expression
/// provides.
fn report_arg_count_mismatch(
&self,
span: Span,
found_span: Option<Span>,
expected_args: Vec<ArgKind>,
found_args: Vec<ArgKind>,
is_closure: bool,
closure_pipe_span: Option<Span>,
) -> DiagnosticBuilder<'tcx, ErrorGuaranteed>;
/// Checks if the type implements one of `Fn`, `FnMut`, or `FnOnce`
/// in that order, and returns the generic type corresponding to the
/// argument of that trait (corresponding to the closure arguments).
fn type_implements_fn_trait(
&self,
param_env: ty::ParamEnv<'tcx>,
ty: ty::Binder<'tcx, Ty<'tcx>>,
polarity: ty::ImplPolarity,
) -> Result<(ty::ClosureKind, ty::Binder<'tcx, Ty<'tcx>>), ()>;
}
impl<'tcx> InferCtxtExt<'tcx> for InferCtxt<'tcx> {
/// Given some node representing a fn-like thing in the HIR map,
/// returns a span and `ArgKind` information that describes the
/// arguments it expects. This can be supplied to
/// `report_arg_count_mismatch`.
fn get_fn_like_arguments(&self, node: Node<'_>) -> Option<(Span, Option<Span>, Vec<ArgKind>)> {
let sm = self.tcx.sess.source_map();
let hir = self.tcx.hir();
Some(match node {
Node::Expr(&hir::Expr {
kind: hir::ExprKind::Closure(&hir::Closure { body, fn_decl_span, fn_arg_span, .. }),
..
}) => (
fn_decl_span,
fn_arg_span,
hir.body(body)
.params
.iter()
.map(|arg| {
if let hir::Pat { kind: hir::PatKind::Tuple(ref args, _), span, .. } =
*arg.pat
{
Some(ArgKind::Tuple(
Some(span),
args.iter()
.map(|pat| {
sm.span_to_snippet(pat.span)
.ok()
.map(|snippet| (snippet, "_".to_owned()))
})
.collect::<Option<Vec<_>>>()?,
))
} else {
let name = sm.span_to_snippet(arg.pat.span).ok()?;
Some(ArgKind::Arg(name, "_".to_owned()))
}
})
.collect::<Option<Vec<ArgKind>>>()?,
),
Node::Item(&hir::Item { kind: hir::ItemKind::Fn(ref sig, ..), .. })
| Node::ImplItem(&hir::ImplItem { kind: hir::ImplItemKind::Fn(ref sig, _), .. })
| Node::TraitItem(&hir::TraitItem {
kind: hir::TraitItemKind::Fn(ref sig, _), ..
}) => (
sig.span,
None,
sig.decl
.inputs
.iter()
.map(|arg| match arg.kind {
hir::TyKind::Tup(ref tys) => ArgKind::Tuple(
Some(arg.span),
vec![("_".to_owned(), "_".to_owned()); tys.len()],
),
_ => ArgKind::empty(),
})
.collect::<Vec<ArgKind>>(),
),
Node::Ctor(ref variant_data) => {
let span = variant_data.ctor_hir_id().map_or(DUMMY_SP, |id| hir.span(id));
(span, None, vec![ArgKind::empty(); variant_data.fields().len()])
}
_ => panic!("non-FnLike node found: {node:?}"),
})
}
/// Reports an error when the number of arguments needed by a
/// trait match doesn't match the number that the expression
/// provides.
fn report_arg_count_mismatch(
&self,
span: Span,
found_span: Option<Span>,
expected_args: Vec<ArgKind>,
found_args: Vec<ArgKind>,
is_closure: bool,
closure_arg_span: Option<Span>,
) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
let kind = if is_closure { "closure" } else { "function" };
let args_str = |arguments: &[ArgKind], other: &[ArgKind]| {
let arg_length = arguments.len();
let distinct = matches!(other, &[ArgKind::Tuple(..)]);
match (arg_length, arguments.get(0)) {
(1, Some(ArgKind::Tuple(_, fields))) => {
format!("a single {}-tuple as argument", fields.len())
}
_ => format!(
"{} {}argument{}",
arg_length,
if distinct && arg_length > 1 { "distinct " } else { "" },
pluralize!(arg_length)
),
}
};
let expected_str = args_str(&expected_args, &found_args);
let found_str = args_str(&found_args, &expected_args);
let mut err = struct_span_err!(
self.tcx.sess,
span,
E0593,
"{} is expected to take {}, but it takes {}",
kind,
expected_str,
found_str,
);
err.span_label(span, format!("expected {kind} that takes {expected_str}"));
if let Some(found_span) = found_span {
err.span_label(found_span, format!("takes {found_str}"));
// Suggest to take and ignore the arguments with expected_args_length `_`s if
// found arguments is empty (assume the user just wants to ignore args in this case).
// For example, if `expected_args_length` is 2, suggest `|_, _|`.
if found_args.is_empty() && is_closure {
let underscores = vec!["_"; expected_args.len()].join(", ");
err.span_suggestion_verbose(
closure_arg_span.unwrap_or(found_span),
format!(
"consider changing the closure to take and ignore the expected argument{}",
pluralize!(expected_args.len())
),
format!("|{underscores}|"),
Applicability::MachineApplicable,
);
}
if let &[ArgKind::Tuple(_, ref fields)] = &found_args[..] {
if fields.len() == expected_args.len() {
let sugg = fields
.iter()
.map(|(name, _)| name.to_owned())
.collect::<Vec<String>>()
.join(", ");
err.span_suggestion_verbose(
found_span,
"change the closure to take multiple arguments instead of a single tuple",
format!("|{sugg}|"),
Applicability::MachineApplicable,
);
}
}
if let &[ArgKind::Tuple(_, ref fields)] = &expected_args[..]
&& fields.len() == found_args.len()
&& is_closure
{
let sugg = format!(
"|({}){}|",
found_args
.iter()
.map(|arg| match arg {
ArgKind::Arg(name, _) => name.to_owned(),
_ => "_".to_owned(),
})
.collect::<Vec<String>>()
.join(", "),
// add type annotations if available
if found_args.iter().any(|arg| match arg {
ArgKind::Arg(_, ty) => ty != "_",
_ => false,
}) {
format!(
": ({})",
fields
.iter()
.map(|(_, ty)| ty.to_owned())
.collect::<Vec<String>>()
.join(", ")
)
} else {
String::new()
},
);
err.span_suggestion_verbose(
found_span,
"change the closure to accept a tuple instead of individual arguments",
sugg,
Applicability::MachineApplicable,
);
}
}
err
}
fn type_implements_fn_trait(
&self,
param_env: ty::ParamEnv<'tcx>,
ty: ty::Binder<'tcx, Ty<'tcx>>,
polarity: ty::ImplPolarity,
) -> Result<(ty::ClosureKind, ty::Binder<'tcx, Ty<'tcx>>), ()> {
self.commit_if_ok(|_| {
for trait_def_id in [
self.tcx.lang_items().fn_trait(),
self.tcx.lang_items().fn_mut_trait(),
self.tcx.lang_items().fn_once_trait(),
] {
let Some(trait_def_id) = trait_def_id else { continue };
// Make a fresh inference variable so we can determine what the substitutions
// of the trait are.
let var = self.next_ty_var(TypeVariableOrigin {
span: DUMMY_SP,
kind: TypeVariableOriginKind::MiscVariable,
});
// FIXME(effects)
let trait_ref = ty::TraitRef::new(self.tcx, trait_def_id, [ty.skip_binder(), var]);
let obligation = Obligation::new(
self.tcx,
ObligationCause::dummy(),
param_env,
ty.rebind(ty::TraitPredicate { trait_ref, polarity }),
);
let ocx = ObligationCtxt::new(self);
ocx.register_obligation(obligation);
if ocx.select_all_or_error().is_empty() {
return Ok((
self.tcx
.fn_trait_kind_from_def_id(trait_def_id)
.expect("expected to map DefId to ClosureKind"),
ty.rebind(self.resolve_vars_if_possible(var)),
));
}
}
Err(())
})
}
}