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-rw-r--r--compiler/rustc_typeck/src/astconv/generics.rs664
1 files changed, 664 insertions, 0 deletions
diff --git a/compiler/rustc_typeck/src/astconv/generics.rs b/compiler/rustc_typeck/src/astconv/generics.rs
new file mode 100644
index 000000000..40aa27a29
--- /dev/null
+++ b/compiler/rustc_typeck/src/astconv/generics.rs
@@ -0,0 +1,664 @@
+use super::IsMethodCall;
+use crate::astconv::{
+ AstConv, CreateSubstsForGenericArgsCtxt, ExplicitLateBound, GenericArgCountMismatch,
+ GenericArgCountResult, GenericArgPosition,
+};
+use crate::errors::AssocTypeBindingNotAllowed;
+use crate::structured_errors::{GenericArgsInfo, StructuredDiagnostic, WrongNumberOfGenericArgs};
+use rustc_ast::ast::ParamKindOrd;
+use rustc_errors::{struct_span_err, Applicability, Diagnostic, MultiSpan};
+use rustc_hir as hir;
+use rustc_hir::def::{DefKind, Res};
+use rustc_hir::def_id::DefId;
+use rustc_hir::GenericArg;
+use rustc_infer::infer::TyCtxtInferExt;
+use rustc_middle::ty::{
+ self, subst, subst::SubstsRef, GenericParamDef, GenericParamDefKind, IsSuggestable, Ty, TyCtxt,
+};
+use rustc_session::lint::builtin::LATE_BOUND_LIFETIME_ARGUMENTS;
+use rustc_span::{symbol::kw, Span};
+use smallvec::SmallVec;
+
+impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
+ /// Report an error that a generic argument did not match the generic parameter that was
+ /// expected.
+ fn generic_arg_mismatch_err(
+ tcx: TyCtxt<'_>,
+ arg: &GenericArg<'_>,
+ param: &GenericParamDef,
+ possible_ordering_error: bool,
+ help: Option<&str>,
+ ) {
+ let sess = tcx.sess;
+ let mut err = struct_span_err!(
+ sess,
+ arg.span(),
+ E0747,
+ "{} provided when a {} was expected",
+ arg.descr(),
+ param.kind.descr(),
+ );
+
+ if let GenericParamDefKind::Const { .. } = param.kind {
+ if matches!(arg, GenericArg::Type(hir::Ty { kind: hir::TyKind::Infer, .. })) {
+ err.help("const arguments cannot yet be inferred with `_`");
+ if sess.is_nightly_build() {
+ err.help(
+ "add `#![feature(generic_arg_infer)]` to the crate attributes to enable",
+ );
+ }
+ }
+ }
+
+ let add_braces_suggestion = |arg: &GenericArg<'_>, err: &mut Diagnostic| {
+ let suggestions = vec![
+ (arg.span().shrink_to_lo(), String::from("{ ")),
+ (arg.span().shrink_to_hi(), String::from(" }")),
+ ];
+ err.multipart_suggestion(
+ "if this generic argument was intended as a const parameter, \
+ surround it with braces",
+ suggestions,
+ Applicability::MaybeIncorrect,
+ );
+ };
+
+ // Specific suggestion set for diagnostics
+ match (arg, &param.kind) {
+ (
+ GenericArg::Type(hir::Ty {
+ kind: hir::TyKind::Path(rustc_hir::QPath::Resolved(_, path)),
+ ..
+ }),
+ GenericParamDefKind::Const { .. },
+ ) => match path.res {
+ Res::Err => {
+ add_braces_suggestion(arg, &mut err);
+ err.set_primary_message(
+ "unresolved item provided when a constant was expected",
+ )
+ .emit();
+ return;
+ }
+ Res::Def(DefKind::TyParam, src_def_id) => {
+ if let Some(param_local_id) = param.def_id.as_local() {
+ let param_name = tcx.hir().ty_param_name(param_local_id);
+ let param_type = tcx.infer_ctxt().enter(|infcx| {
+ infcx.resolve_numeric_literals_with_default(tcx.type_of(param.def_id))
+ });
+ if param_type.is_suggestable(tcx, false) {
+ err.span_suggestion(
+ tcx.def_span(src_def_id),
+ "consider changing this type parameter to be a `const` generic",
+ format!("const {}: {}", param_name, param_type),
+ Applicability::MaybeIncorrect,
+ );
+ };
+ }
+ }
+ _ => add_braces_suggestion(arg, &mut err),
+ },
+ (
+ GenericArg::Type(hir::Ty { kind: hir::TyKind::Path(_), .. }),
+ GenericParamDefKind::Const { .. },
+ ) => add_braces_suggestion(arg, &mut err),
+ (
+ GenericArg::Type(hir::Ty { kind: hir::TyKind::Array(_, len), .. }),
+ GenericParamDefKind::Const { .. },
+ ) if tcx.type_of(param.def_id) == tcx.types.usize => {
+ let snippet = sess.source_map().span_to_snippet(tcx.hir().span(len.hir_id()));
+ if let Ok(snippet) = snippet {
+ err.span_suggestion(
+ arg.span(),
+ "array type provided where a `usize` was expected, try",
+ format!("{{ {} }}", snippet),
+ Applicability::MaybeIncorrect,
+ );
+ }
+ }
+ (GenericArg::Const(cnst), GenericParamDefKind::Type { .. }) => {
+ let body = tcx.hir().body(cnst.value.body);
+ if let rustc_hir::ExprKind::Path(rustc_hir::QPath::Resolved(_, path)) =
+ body.value.kind
+ {
+ if let Res::Def(DefKind::Fn { .. }, id) = path.res {
+ err.help(&format!(
+ "`{}` is a function item, not a type",
+ tcx.item_name(id)
+ ));
+ err.help("function item types cannot be named directly");
+ }
+ }
+ }
+ _ => {}
+ }
+
+ let kind_ord = param.kind.to_ord();
+ let arg_ord = arg.to_ord();
+
+ // This note is only true when generic parameters are strictly ordered by their kind.
+ if possible_ordering_error && kind_ord.cmp(&arg_ord) != core::cmp::Ordering::Equal {
+ let (first, last) = if kind_ord < arg_ord {
+ (param.kind.descr(), arg.descr())
+ } else {
+ (arg.descr(), param.kind.descr())
+ };
+ err.note(&format!("{} arguments must be provided before {} arguments", first, last));
+ if let Some(help) = help {
+ err.help(help);
+ }
+ }
+
+ err.emit();
+ }
+
+ /// Creates the relevant generic argument substitutions
+ /// corresponding to a set of generic parameters. This is a
+ /// rather complex function. Let us try to explain the role
+ /// of each of its parameters:
+ ///
+ /// To start, we are given the `def_id` of the thing we are
+ /// creating the substitutions for, and a partial set of
+ /// substitutions `parent_substs`. In general, the substitutions
+ /// for an item begin with substitutions for all the "parents" of
+ /// that item -- e.g., for a method it might include the
+ /// parameters from the impl.
+ ///
+ /// Therefore, the method begins by walking down these parents,
+ /// starting with the outermost parent and proceed inwards until
+ /// it reaches `def_id`. For each parent `P`, it will check `parent_substs`
+ /// first to see if the parent's substitutions are listed in there. If so,
+ /// we can append those and move on. Otherwise, it invokes the
+ /// three callback functions:
+ ///
+ /// - `args_for_def_id`: given the `DefId` `P`, supplies back the
+ /// generic arguments that were given to that parent from within
+ /// the path; so e.g., if you have `<T as Foo>::Bar`, the `DefId`
+ /// might refer to the trait `Foo`, and the arguments might be
+ /// `[T]`. The boolean value indicates whether to infer values
+ /// for arguments whose values were not explicitly provided.
+ /// - `provided_kind`: given the generic parameter and the value from `args_for_def_id`,
+ /// instantiate a `GenericArg`.
+ /// - `inferred_kind`: if no parameter was provided, and inference is enabled, then
+ /// creates a suitable inference variable.
+ pub fn create_substs_for_generic_args<'a>(
+ tcx: TyCtxt<'tcx>,
+ def_id: DefId,
+ parent_substs: &[subst::GenericArg<'tcx>],
+ has_self: bool,
+ self_ty: Option<Ty<'tcx>>,
+ arg_count: &GenericArgCountResult,
+ ctx: &mut impl CreateSubstsForGenericArgsCtxt<'a, 'tcx>,
+ ) -> SubstsRef<'tcx> {
+ // Collect the segments of the path; we need to substitute arguments
+ // for parameters throughout the entire path (wherever there are
+ // generic parameters).
+ let mut parent_defs = tcx.generics_of(def_id);
+ let count = parent_defs.count();
+ let mut stack = vec![(def_id, parent_defs)];
+ while let Some(def_id) = parent_defs.parent {
+ parent_defs = tcx.generics_of(def_id);
+ stack.push((def_id, parent_defs));
+ }
+
+ // We manually build up the substitution, rather than using convenience
+ // methods in `subst.rs`, so that we can iterate over the arguments and
+ // parameters in lock-step linearly, instead of trying to match each pair.
+ let mut substs: SmallVec<[subst::GenericArg<'tcx>; 8]> = SmallVec::with_capacity(count);
+ // Iterate over each segment of the path.
+ while let Some((def_id, defs)) = stack.pop() {
+ let mut params = defs.params.iter().peekable();
+
+ // If we have already computed substitutions for parents, we can use those directly.
+ while let Some(&param) = params.peek() {
+ if let Some(&kind) = parent_substs.get(param.index as usize) {
+ substs.push(kind);
+ params.next();
+ } else {
+ break;
+ }
+ }
+
+ // `Self` is handled first, unless it's been handled in `parent_substs`.
+ if has_self {
+ if let Some(&param) = params.peek() {
+ if param.index == 0 {
+ if let GenericParamDefKind::Type { .. } = param.kind {
+ substs.push(
+ self_ty
+ .map(|ty| ty.into())
+ .unwrap_or_else(|| ctx.inferred_kind(None, param, true)),
+ );
+ params.next();
+ }
+ }
+ }
+ }
+
+ // Check whether this segment takes generic arguments and the user has provided any.
+ let (generic_args, infer_args) = ctx.args_for_def_id(def_id);
+
+ let args_iter = generic_args.iter().flat_map(|generic_args| generic_args.args.iter());
+ let mut args = args_iter.clone().peekable();
+
+ // If we encounter a type or const when we expect a lifetime, we infer the lifetimes.
+ // If we later encounter a lifetime, we know that the arguments were provided in the
+ // wrong order. `force_infer_lt` records the type or const that forced lifetimes to be
+ // inferred, so we can use it for diagnostics later.
+ let mut force_infer_lt = None;
+
+ loop {
+ // We're going to iterate through the generic arguments that the user
+ // provided, matching them with the generic parameters we expect.
+ // Mismatches can occur as a result of elided lifetimes, or for malformed
+ // input. We try to handle both sensibly.
+ match (args.peek(), params.peek()) {
+ (Some(&arg), Some(&param)) => {
+ match (arg, &param.kind, arg_count.explicit_late_bound) {
+ (GenericArg::Lifetime(_), GenericParamDefKind::Lifetime, _)
+ | (
+ GenericArg::Type(_) | GenericArg::Infer(_),
+ GenericParamDefKind::Type { .. },
+ _,
+ )
+ | (
+ GenericArg::Const(_) | GenericArg::Infer(_),
+ GenericParamDefKind::Const { .. },
+ _,
+ ) => {
+ substs.push(ctx.provided_kind(param, arg));
+ args.next();
+ params.next();
+ }
+ (
+ GenericArg::Infer(_) | GenericArg::Type(_) | GenericArg::Const(_),
+ GenericParamDefKind::Lifetime,
+ _,
+ ) => {
+ // We expected a lifetime argument, but got a type or const
+ // argument. That means we're inferring the lifetimes.
+ substs.push(ctx.inferred_kind(None, param, infer_args));
+ force_infer_lt = Some((arg, param));
+ params.next();
+ }
+ (GenericArg::Lifetime(_), _, ExplicitLateBound::Yes) => {
+ // We've come across a lifetime when we expected something else in
+ // the presence of explicit late bounds. This is most likely
+ // due to the presence of the explicit bound so we're just going to
+ // ignore it.
+ args.next();
+ }
+ (_, _, _) => {
+ // We expected one kind of parameter, but the user provided
+ // another. This is an error. However, if we already know that
+ // the arguments don't match up with the parameters, we won't issue
+ // an additional error, as the user already knows what's wrong.
+ if arg_count.correct.is_ok() {
+ // We're going to iterate over the parameters to sort them out, and
+ // show that order to the user as a possible order for the parameters
+ let mut param_types_present = defs
+ .params
+ .clone()
+ .into_iter()
+ .map(|param| (param.kind.to_ord(), param))
+ .collect::<Vec<(ParamKindOrd, GenericParamDef)>>();
+ param_types_present.sort_by_key(|(ord, _)| *ord);
+ let (mut param_types_present, ordered_params): (
+ Vec<ParamKindOrd>,
+ Vec<GenericParamDef>,
+ ) = param_types_present.into_iter().unzip();
+ param_types_present.dedup();
+
+ Self::generic_arg_mismatch_err(
+ tcx,
+ arg,
+ param,
+ !args_iter.clone().is_sorted_by_key(|arg| arg.to_ord()),
+ Some(&format!(
+ "reorder the arguments: {}: `<{}>`",
+ param_types_present
+ .into_iter()
+ .map(|ord| format!("{}s", ord))
+ .collect::<Vec<String>>()
+ .join(", then "),
+ ordered_params
+ .into_iter()
+ .filter_map(|param| {
+ if param.name == kw::SelfUpper {
+ None
+ } else {
+ Some(param.name.to_string())
+ }
+ })
+ .collect::<Vec<String>>()
+ .join(", ")
+ )),
+ );
+ }
+
+ // We've reported the error, but we want to make sure that this
+ // problem doesn't bubble down and create additional, irrelevant
+ // errors. In this case, we're simply going to ignore the argument
+ // and any following arguments. The rest of the parameters will be
+ // inferred.
+ while args.next().is_some() {}
+ }
+ }
+ }
+
+ (Some(&arg), None) => {
+ // We should never be able to reach this point with well-formed input.
+ // There are three situations in which we can encounter this issue.
+ //
+ // 1. The number of arguments is incorrect. In this case, an error
+ // will already have been emitted, and we can ignore it.
+ // 2. There are late-bound lifetime parameters present, yet the
+ // lifetime arguments have also been explicitly specified by the
+ // user.
+ // 3. We've inferred some lifetimes, which have been provided later (i.e.
+ // after a type or const). We want to throw an error in this case.
+
+ if arg_count.correct.is_ok()
+ && arg_count.explicit_late_bound == ExplicitLateBound::No
+ {
+ let kind = arg.descr();
+ assert_eq!(kind, "lifetime");
+ let (provided_arg, param) =
+ force_infer_lt.expect("lifetimes ought to have been inferred");
+ Self::generic_arg_mismatch_err(tcx, provided_arg, param, false, None);
+ }
+
+ break;
+ }
+
+ (None, Some(&param)) => {
+ // If there are fewer arguments than parameters, it means
+ // we're inferring the remaining arguments.
+ substs.push(ctx.inferred_kind(Some(&substs), param, infer_args));
+ params.next();
+ }
+
+ (None, None) => break,
+ }
+ }
+ }
+
+ tcx.intern_substs(&substs)
+ }
+
+ /// Checks that the correct number of generic arguments have been provided.
+ /// Used specifically for function calls.
+ pub fn check_generic_arg_count_for_call(
+ tcx: TyCtxt<'_>,
+ span: Span,
+ def_id: DefId,
+ generics: &ty::Generics,
+ seg: &hir::PathSegment<'_>,
+ is_method_call: IsMethodCall,
+ ) -> GenericArgCountResult {
+ let empty_args = hir::GenericArgs::none();
+ let gen_args = seg.args.unwrap_or(&empty_args);
+ let gen_pos = if is_method_call == IsMethodCall::Yes {
+ GenericArgPosition::MethodCall
+ } else {
+ GenericArgPosition::Value
+ };
+ let has_self = generics.parent.is_none() && generics.has_self;
+
+ Self::check_generic_arg_count(
+ tcx,
+ span,
+ def_id,
+ seg,
+ generics,
+ gen_args,
+ gen_pos,
+ has_self,
+ seg.infer_args,
+ )
+ }
+
+ /// Checks that the correct number of generic arguments have been provided.
+ /// This is used both for datatypes and function calls.
+ #[instrument(skip(tcx, gen_pos), level = "debug")]
+ pub(crate) fn check_generic_arg_count(
+ tcx: TyCtxt<'_>,
+ span: Span,
+ def_id: DefId,
+ seg: &hir::PathSegment<'_>,
+ gen_params: &ty::Generics,
+ gen_args: &hir::GenericArgs<'_>,
+ gen_pos: GenericArgPosition,
+ has_self: bool,
+ infer_args: bool,
+ ) -> GenericArgCountResult {
+ let default_counts = gen_params.own_defaults();
+ let param_counts = gen_params.own_counts();
+
+ // Subtracting from param count to ensure type params synthesized from `impl Trait`
+ // cannot be explicitly specified.
+ let synth_type_param_count = gen_params
+ .params
+ .iter()
+ .filter(|param| {
+ matches!(param.kind, ty::GenericParamDefKind::Type { synthetic: true, .. })
+ })
+ .count();
+ let named_type_param_count =
+ param_counts.types - has_self as usize - synth_type_param_count;
+ let infer_lifetimes =
+ (gen_pos != GenericArgPosition::Type || infer_args) && !gen_args.has_lifetime_params();
+
+ if gen_pos != GenericArgPosition::Type && !gen_args.bindings.is_empty() {
+ Self::prohibit_assoc_ty_binding(tcx, gen_args.bindings[0].span);
+ }
+
+ let explicit_late_bound =
+ Self::prohibit_explicit_late_bound_lifetimes(tcx, gen_params, gen_args, gen_pos);
+
+ let mut invalid_args = vec![];
+
+ let mut check_lifetime_args =
+ |min_expected_args: usize,
+ max_expected_args: usize,
+ provided_args: usize,
+ late_bounds_ignore: bool| {
+ if (min_expected_args..=max_expected_args).contains(&provided_args) {
+ return Ok(());
+ }
+
+ if late_bounds_ignore {
+ return Ok(());
+ }
+
+ if provided_args > max_expected_args {
+ invalid_args.extend(
+ gen_args.args[max_expected_args..provided_args]
+ .iter()
+ .map(|arg| arg.span()),
+ );
+ };
+
+ let gen_args_info = if provided_args > min_expected_args {
+ invalid_args.extend(
+ gen_args.args[min_expected_args..provided_args]
+ .iter()
+ .map(|arg| arg.span()),
+ );
+ let num_redundant_args = provided_args - min_expected_args;
+ GenericArgsInfo::ExcessLifetimes { num_redundant_args }
+ } else {
+ let num_missing_args = min_expected_args - provided_args;
+ GenericArgsInfo::MissingLifetimes { num_missing_args }
+ };
+
+ let reported = WrongNumberOfGenericArgs::new(
+ tcx,
+ gen_args_info,
+ seg,
+ gen_params,
+ has_self as usize,
+ gen_args,
+ def_id,
+ )
+ .diagnostic()
+ .emit();
+
+ Err(reported)
+ };
+
+ let min_expected_lifetime_args = if infer_lifetimes { 0 } else { param_counts.lifetimes };
+ let max_expected_lifetime_args = param_counts.lifetimes;
+ let num_provided_lifetime_args = gen_args.num_lifetime_params();
+
+ let lifetimes_correct = check_lifetime_args(
+ min_expected_lifetime_args,
+ max_expected_lifetime_args,
+ num_provided_lifetime_args,
+ explicit_late_bound == ExplicitLateBound::Yes,
+ );
+
+ let mut check_types_and_consts = |expected_min,
+ expected_max,
+ expected_max_with_synth,
+ provided,
+ params_offset,
+ args_offset| {
+ debug!(
+ ?expected_min,
+ ?expected_max,
+ ?provided,
+ ?params_offset,
+ ?args_offset,
+ "check_types_and_consts"
+ );
+ if (expected_min..=expected_max).contains(&provided) {
+ return Ok(());
+ }
+
+ let num_default_params = expected_max - expected_min;
+
+ let gen_args_info = if provided > expected_max {
+ invalid_args.extend(
+ gen_args.args[args_offset + expected_max..args_offset + provided]
+ .iter()
+ .map(|arg| arg.span()),
+ );
+ let num_redundant_args = provided - expected_max;
+
+ // Provide extra note if synthetic arguments like `impl Trait` are specified.
+ let synth_provided = provided <= expected_max_with_synth;
+
+ GenericArgsInfo::ExcessTypesOrConsts {
+ num_redundant_args,
+ num_default_params,
+ args_offset,
+ synth_provided,
+ }
+ } else {
+ let num_missing_args = expected_max - provided;
+
+ GenericArgsInfo::MissingTypesOrConsts {
+ num_missing_args,
+ num_default_params,
+ args_offset,
+ }
+ };
+
+ debug!(?gen_args_info);
+
+ let reported = WrongNumberOfGenericArgs::new(
+ tcx,
+ gen_args_info,
+ seg,
+ gen_params,
+ params_offset,
+ gen_args,
+ def_id,
+ )
+ .diagnostic()
+ .emit_unless(gen_args.has_err());
+
+ Err(reported)
+ };
+
+ let args_correct = {
+ let expected_min = if infer_args {
+ 0
+ } else {
+ param_counts.consts + named_type_param_count
+ - default_counts.types
+ - default_counts.consts
+ };
+ debug!(?expected_min);
+ debug!(arg_counts.lifetimes=?gen_args.num_lifetime_params());
+
+ check_types_and_consts(
+ expected_min,
+ param_counts.consts + named_type_param_count,
+ param_counts.consts + named_type_param_count + synth_type_param_count,
+ gen_args.num_generic_params(),
+ param_counts.lifetimes + has_self as usize,
+ gen_args.num_lifetime_params(),
+ )
+ };
+
+ GenericArgCountResult {
+ explicit_late_bound,
+ correct: lifetimes_correct.and(args_correct).map_err(|reported| {
+ GenericArgCountMismatch { reported: Some(reported), invalid_args }
+ }),
+ }
+ }
+
+ /// Emits an error regarding forbidden type binding associations
+ pub fn prohibit_assoc_ty_binding(tcx: TyCtxt<'_>, span: Span) {
+ tcx.sess.emit_err(AssocTypeBindingNotAllowed { span });
+ }
+
+ /// Prohibits explicit lifetime arguments if late-bound lifetime parameters
+ /// are present. This is used both for datatypes and function calls.
+ pub(crate) fn prohibit_explicit_late_bound_lifetimes(
+ tcx: TyCtxt<'_>,
+ def: &ty::Generics,
+ args: &hir::GenericArgs<'_>,
+ position: GenericArgPosition,
+ ) -> ExplicitLateBound {
+ let param_counts = def.own_counts();
+ let infer_lifetimes = position != GenericArgPosition::Type && !args.has_lifetime_params();
+
+ if infer_lifetimes {
+ return ExplicitLateBound::No;
+ }
+
+ if let Some(span_late) = def.has_late_bound_regions {
+ let msg = "cannot specify lifetime arguments explicitly \
+ if late bound lifetime parameters are present";
+ let note = "the late bound lifetime parameter is introduced here";
+ let span = args.args[0].span();
+
+ if position == GenericArgPosition::Value
+ && args.num_lifetime_params() != param_counts.lifetimes
+ {
+ let mut err = tcx.sess.struct_span_err(span, msg);
+ err.span_note(span_late, note);
+ err.emit();
+ } else {
+ let mut multispan = MultiSpan::from_span(span);
+ multispan.push_span_label(span_late, note);
+ tcx.struct_span_lint_hir(
+ LATE_BOUND_LIFETIME_ARGUMENTS,
+ args.args[0].id(),
+ multispan,
+ |lint| {
+ lint.build(msg).emit();
+ },
+ );
+ }
+
+ ExplicitLateBound::Yes
+ } else {
+ ExplicitLateBound::No
+ }
+ }
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-06-12 14:15:29 +0000