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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-17 12:11:38 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-17 12:13:23 +0000
commit20431706a863f92cb37dc512fef6e48d192aaf2c (patch)
tree2867f13f5fd5437ba628c67d7f87309ccadcd286 /compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
parentReleasing progress-linux version 1.65.0+dfsg1-2~progress7.99u1. (diff)
downloadrustc-20431706a863f92cb37dc512fef6e48d192aaf2c.tar.xz
rustc-20431706a863f92cb37dc512fef6e48d192aaf2c.zip
Merging upstream version 1.66.0+dfsg1.
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs')
-rw-r--r--compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs2236
1 files changed, 2236 insertions, 0 deletions
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
new file mode 100644
index 000000000..8e0fcb56c
--- /dev/null
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
@@ -0,0 +1,2236 @@
+use crate::coercion::CoerceMany;
+use crate::fn_ctxt::arg_matrix::{ArgMatrix, Compatibility, Error, ExpectedIdx, ProvidedIdx};
+use crate::gather_locals::Declaration;
+use crate::method::MethodCallee;
+use crate::Expectation::*;
+use crate::TupleArgumentsFlag::*;
+use crate::{
+ struct_span_err, BreakableCtxt, Diverges, Expectation, FnCtxt, LocalTy, Needs,
+ TupleArgumentsFlag,
+};
+use rustc_ast as ast;
+use rustc_data_structures::fx::FxHashSet;
+use rustc_errors::{pluralize, Applicability, Diagnostic, DiagnosticId, MultiSpan};
+use rustc_hir as hir;
+use rustc_hir::def::{CtorOf, DefKind, Res};
+use rustc_hir::def_id::DefId;
+use rustc_hir::{ExprKind, Node, QPath};
+use rustc_hir_analysis::astconv::AstConv;
+use rustc_hir_analysis::check::intrinsicck::InlineAsmCtxt;
+use rustc_hir_analysis::check::potentially_plural_count;
+use rustc_hir_analysis::structured_errors::StructuredDiagnostic;
+use rustc_index::vec::IndexVec;
+use rustc_infer::infer::error_reporting::{FailureCode, ObligationCauseExt};
+use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
+use rustc_infer::infer::InferOk;
+use rustc_infer::infer::TypeTrace;
+use rustc_middle::ty::adjustment::AllowTwoPhase;
+use rustc_middle::ty::visit::TypeVisitable;
+use rustc_middle::ty::{self, DefIdTree, IsSuggestable, Ty, TypeSuperVisitable, TypeVisitor};
+use rustc_session::Session;
+use rustc_span::symbol::Ident;
+use rustc_span::{self, sym, Span};
+use rustc_trait_selection::traits::{self, ObligationCauseCode, SelectionContext};
+
+use std::iter;
+use std::mem;
+use std::ops::ControlFlow;
+use std::slice;
+
+impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
+ pub(in super::super) fn check_casts(&mut self) {
+ // don't hold the borrow to deferred_cast_checks while checking to avoid borrow checker errors
+ // when writing to `self.param_env`.
+ let mut deferred_cast_checks = mem::take(&mut *self.deferred_cast_checks.borrow_mut());
+
+ debug!("FnCtxt::check_casts: {} deferred checks", deferred_cast_checks.len());
+ for cast in deferred_cast_checks.drain(..) {
+ let prev_env = self.param_env;
+ self.param_env = self.param_env.with_constness(cast.constness);
+
+ cast.check(self);
+
+ self.param_env = prev_env;
+ }
+
+ *self.deferred_cast_checks.borrow_mut() = deferred_cast_checks;
+ }
+
+ pub(in super::super) fn check_transmutes(&self) {
+ let mut deferred_transmute_checks = self.deferred_transmute_checks.borrow_mut();
+ debug!("FnCtxt::check_transmutes: {} deferred checks", deferred_transmute_checks.len());
+ for (from, to, hir_id) in deferred_transmute_checks.drain(..) {
+ self.check_transmute(from, to, hir_id);
+ }
+ }
+
+ pub(in super::super) fn check_asms(&self) {
+ let mut deferred_asm_checks = self.deferred_asm_checks.borrow_mut();
+ debug!("FnCtxt::check_asm: {} deferred checks", deferred_asm_checks.len());
+ for (asm, hir_id) in deferred_asm_checks.drain(..) {
+ let enclosing_id = self.tcx.hir().enclosing_body_owner(hir_id);
+ let get_operand_ty = |expr| {
+ let ty = self.typeck_results.borrow().expr_ty_adjusted(expr);
+ let ty = self.resolve_vars_if_possible(ty);
+ if ty.has_non_region_infer() {
+ assert!(self.is_tainted_by_errors());
+ self.tcx.ty_error()
+ } else {
+ self.tcx.erase_regions(ty)
+ }
+ };
+ InlineAsmCtxt::new_in_fn(self.tcx, self.param_env, get_operand_ty)
+ .check_asm(asm, self.tcx.hir().local_def_id_to_hir_id(enclosing_id));
+ }
+ }
+
+ pub(in super::super) fn check_method_argument_types(
+ &self,
+ sp: Span,
+ expr: &'tcx hir::Expr<'tcx>,
+ method: Result<MethodCallee<'tcx>, ()>,
+ args_no_rcvr: &'tcx [hir::Expr<'tcx>],
+ tuple_arguments: TupleArgumentsFlag,
+ expected: Expectation<'tcx>,
+ ) -> Ty<'tcx> {
+ let has_error = match method {
+ Ok(method) => method.substs.references_error() || method.sig.references_error(),
+ Err(_) => true,
+ };
+ if has_error {
+ let err_inputs = self.err_args(args_no_rcvr.len());
+
+ let err_inputs = match tuple_arguments {
+ DontTupleArguments => err_inputs,
+ TupleArguments => vec![self.tcx.intern_tup(&err_inputs)],
+ };
+
+ self.check_argument_types(
+ sp,
+ expr,
+ &err_inputs,
+ None,
+ args_no_rcvr,
+ false,
+ tuple_arguments,
+ method.ok().map(|method| method.def_id),
+ );
+ return self.tcx.ty_error();
+ }
+
+ let method = method.unwrap();
+ // HACK(eddyb) ignore self in the definition (see above).
+ let expected_input_tys = self.expected_inputs_for_expected_output(
+ sp,
+ expected,
+ method.sig.output(),
+ &method.sig.inputs()[1..],
+ );
+ self.check_argument_types(
+ sp,
+ expr,
+ &method.sig.inputs()[1..],
+ expected_input_tys,
+ args_no_rcvr,
+ method.sig.c_variadic,
+ tuple_arguments,
+ Some(method.def_id),
+ );
+ method.sig.output()
+ }
+
+ /// Generic function that factors out common logic from function calls,
+ /// method calls and overloaded operators.
+ pub(in super::super) fn check_argument_types(
+ &self,
+ // Span enclosing the call site
+ call_span: Span,
+ // Expression of the call site
+ call_expr: &'tcx hir::Expr<'tcx>,
+ // Types (as defined in the *signature* of the target function)
+ formal_input_tys: &[Ty<'tcx>],
+ // More specific expected types, after unifying with caller output types
+ expected_input_tys: Option<Vec<Ty<'tcx>>>,
+ // The expressions for each provided argument
+ provided_args: &'tcx [hir::Expr<'tcx>],
+ // Whether the function is variadic, for example when imported from C
+ c_variadic: bool,
+ // Whether the arguments have been bundled in a tuple (ex: closures)
+ tuple_arguments: TupleArgumentsFlag,
+ // The DefId for the function being called, for better error messages
+ fn_def_id: Option<DefId>,
+ ) {
+ let tcx = self.tcx;
+
+ // Conceptually, we've got some number of expected inputs, and some number of provided arguments
+ // and we can form a grid of whether each argument could satisfy a given input:
+ // in1 | in2 | in3 | ...
+ // arg1 ? | | |
+ // arg2 | ? | |
+ // arg3 | | ? |
+ // ...
+ // Initially, we just check the diagonal, because in the case of correct code
+ // these are the only checks that matter
+ // However, in the unhappy path, we'll fill in this whole grid to attempt to provide
+ // better error messages about invalid method calls.
+
+ // All the input types from the fn signature must outlive the call
+ // so as to validate implied bounds.
+ for (&fn_input_ty, arg_expr) in iter::zip(formal_input_tys, provided_args) {
+ self.register_wf_obligation(fn_input_ty.into(), arg_expr.span, traits::MiscObligation);
+ }
+
+ let mut err_code = "E0061";
+
+ // If the arguments should be wrapped in a tuple (ex: closures), unwrap them here
+ let (formal_input_tys, expected_input_tys) = if tuple_arguments == TupleArguments {
+ let tuple_type = self.structurally_resolved_type(call_span, formal_input_tys[0]);
+ match tuple_type.kind() {
+ // We expected a tuple and got a tuple
+ ty::Tuple(arg_types) => {
+ // Argument length differs
+ if arg_types.len() != provided_args.len() {
+ err_code = "E0057";
+ }
+ let expected_input_tys = match expected_input_tys {
+ Some(expected_input_tys) => match expected_input_tys.get(0) {
+ Some(ty) => match ty.kind() {
+ ty::Tuple(tys) => Some(tys.iter().collect()),
+ _ => None,
+ },
+ None => None,
+ },
+ None => None,
+ };
+ (arg_types.iter().collect(), expected_input_tys)
+ }
+ _ => {
+ // Otherwise, there's a mismatch, so clear out what we're expecting, and set
+ // our input types to err_args so we don't blow up the error messages
+ struct_span_err!(
+ tcx.sess,
+ call_span,
+ E0059,
+ "cannot use call notation; the first type parameter \
+ for the function trait is neither a tuple nor unit"
+ )
+ .emit();
+ (self.err_args(provided_args.len()), None)
+ }
+ }
+ } else {
+ (formal_input_tys.to_vec(), expected_input_tys)
+ };
+
+ // If there are no external expectations at the call site, just use the types from the function defn
+ let expected_input_tys = if let Some(expected_input_tys) = expected_input_tys {
+ assert_eq!(expected_input_tys.len(), formal_input_tys.len());
+ expected_input_tys
+ } else {
+ formal_input_tys.clone()
+ };
+
+ let minimum_input_count = expected_input_tys.len();
+ let provided_arg_count = provided_args.len();
+
+ let is_const_eval_select = matches!(fn_def_id, Some(def_id) if
+ self.tcx.def_kind(def_id) == hir::def::DefKind::Fn
+ && self.tcx.is_intrinsic(def_id)
+ && self.tcx.item_name(def_id) == sym::const_eval_select);
+
+ // We introduce a helper function to demand that a given argument satisfy a given input
+ // This is more complicated than just checking type equality, as arguments could be coerced
+ // This version writes those types back so further type checking uses the narrowed types
+ let demand_compatible = |idx| {
+ let formal_input_ty: Ty<'tcx> = formal_input_tys[idx];
+ let expected_input_ty: Ty<'tcx> = expected_input_tys[idx];
+ let provided_arg = &provided_args[idx];
+
+ debug!("checking argument {}: {:?} = {:?}", idx, provided_arg, formal_input_ty);
+
+ // We're on the happy path here, so we'll do a more involved check and write back types
+ // To check compatibility, we'll do 3 things:
+ // 1. Unify the provided argument with the expected type
+ let expectation = Expectation::rvalue_hint(self, expected_input_ty);
+
+ let checked_ty = self.check_expr_with_expectation(provided_arg, expectation);
+
+ // 2. Coerce to the most detailed type that could be coerced
+ // to, which is `expected_ty` if `rvalue_hint` returns an
+ // `ExpectHasType(expected_ty)`, or the `formal_ty` otherwise.
+ let coerced_ty = expectation.only_has_type(self).unwrap_or(formal_input_ty);
+
+ // Cause selection errors caused by resolving a single argument to point at the
+ // argument and not the call. This lets us customize the span pointed to in the
+ // fulfillment error to be more accurate.
+ let coerced_ty = self.resolve_vars_with_obligations(coerced_ty);
+
+ let coerce_error = self
+ .try_coerce(provided_arg, checked_ty, coerced_ty, AllowTwoPhase::Yes, None)
+ .err();
+
+ if coerce_error.is_some() {
+ return Compatibility::Incompatible(coerce_error);
+ }
+
+ // Check that second and third argument of `const_eval_select` must be `FnDef`, and additionally that
+ // the second argument must be `const fn`. The first argument must be a tuple, but this is already expressed
+ // in the function signature (`F: FnOnce<ARG>`), so I did not bother to add another check here.
+ //
+ // This check is here because there is currently no way to express a trait bound for `FnDef` types only.
+ if is_const_eval_select && (1..=2).contains(&idx) {
+ if let ty::FnDef(def_id, _) = checked_ty.kind() {
+ if idx == 1 && !self.tcx.is_const_fn_raw(*def_id) {
+ self.tcx
+ .sess
+ .struct_span_err(provided_arg.span, "this argument must be a `const fn`")
+ .help("consult the documentation on `const_eval_select` for more information")
+ .emit();
+ }
+ } else {
+ self.tcx
+ .sess
+ .struct_span_err(provided_arg.span, "this argument must be a function item")
+ .note(format!("expected a function item, found {checked_ty}"))
+ .help(
+ "consult the documentation on `const_eval_select` for more information",
+ )
+ .emit();
+ }
+ }
+
+ // 3. Check if the formal type is a supertype of the checked one
+ // and register any such obligations for future type checks
+ let supertype_error = self
+ .at(&self.misc(provided_arg.span), self.param_env)
+ .sup(formal_input_ty, coerced_ty);
+ let subtyping_error = match supertype_error {
+ Ok(InferOk { obligations, value: () }) => {
+ self.register_predicates(obligations);
+ None
+ }
+ Err(err) => Some(err),
+ };
+
+ // If neither check failed, the types are compatible
+ match subtyping_error {
+ None => Compatibility::Compatible,
+ Some(_) => Compatibility::Incompatible(subtyping_error),
+ }
+ };
+
+ // To start, we only care "along the diagonal", where we expect every
+ // provided arg to be in the right spot
+ let mut compatibility_diagonal =
+ vec![Compatibility::Incompatible(None); provided_args.len()];
+
+ // Keep track of whether we *could possibly* be satisfied, i.e. whether we're on the happy path
+ // if the wrong number of arguments were supplied, we CAN'T be satisfied,
+ // and if we're c_variadic, the supplied arguments must be >= the minimum count from the function
+ // otherwise, they need to be identical, because rust doesn't currently support variadic functions
+ let mut call_appears_satisfied = if c_variadic {
+ provided_arg_count >= minimum_input_count
+ } else {
+ provided_arg_count == minimum_input_count
+ };
+
+ // Check the arguments.
+ // We do this in a pretty awful way: first we type-check any arguments
+ // that are not closures, then we type-check the closures. This is so
+ // that we have more information about the types of arguments when we
+ // type-check the functions. This isn't really the right way to do this.
+ for check_closures in [false, true] {
+ // More awful hacks: before we check argument types, try to do
+ // an "opportunistic" trait resolution of any trait bounds on
+ // the call. This helps coercions.
+ if check_closures {
+ self.select_obligations_where_possible(false, |_| {})
+ }
+
+ // Check each argument, to satisfy the input it was provided for
+ // Visually, we're traveling down the diagonal of the compatibility matrix
+ for (idx, arg) in provided_args.iter().enumerate() {
+ // Warn only for the first loop (the "no closures" one).
+ // Closure arguments themselves can't be diverging, but
+ // a previous argument can, e.g., `foo(panic!(), || {})`.
+ if !check_closures {
+ self.warn_if_unreachable(arg.hir_id, arg.span, "expression");
+ }
+
+ // For C-variadic functions, we don't have a declared type for all of
+ // the arguments hence we only do our usual type checking with
+ // the arguments who's types we do know. However, we *can* check
+ // for unreachable expressions (see above).
+ // FIXME: unreachable warning current isn't emitted
+ if idx >= minimum_input_count {
+ continue;
+ }
+
+ let is_closure = matches!(arg.kind, ExprKind::Closure { .. });
+ if is_closure != check_closures {
+ continue;
+ }
+
+ let compatible = demand_compatible(idx);
+ let is_compatible = matches!(compatible, Compatibility::Compatible);
+ compatibility_diagonal[idx] = compatible;
+
+ if !is_compatible {
+ call_appears_satisfied = false;
+ }
+ }
+ }
+
+ if c_variadic && provided_arg_count < minimum_input_count {
+ err_code = "E0060";
+ }
+
+ for arg in provided_args.iter().skip(minimum_input_count) {
+ // Make sure we've checked this expr at least once.
+ let arg_ty = self.check_expr(&arg);
+
+ // If the function is c-style variadic, we skipped a bunch of arguments
+ // so we need to check those, and write out the types
+ // Ideally this would be folded into the above, for uniform style
+ // but c-variadic is already a corner case
+ if c_variadic {
+ fn variadic_error<'tcx>(
+ sess: &'tcx Session,
+ span: Span,
+ ty: Ty<'tcx>,
+ cast_ty: &str,
+ ) {
+ use rustc_hir_analysis::structured_errors::MissingCastForVariadicArg;
+
+ MissingCastForVariadicArg { sess, span, ty, cast_ty }.diagnostic().emit();
+ }
+
+ // There are a few types which get autopromoted when passed via varargs
+ // in C but we just error out instead and require explicit casts.
+ let arg_ty = self.structurally_resolved_type(arg.span, arg_ty);
+ match arg_ty.kind() {
+ ty::Float(ty::FloatTy::F32) => {
+ variadic_error(tcx.sess, arg.span, arg_ty, "c_double");
+ }
+ ty::Int(ty::IntTy::I8 | ty::IntTy::I16) | ty::Bool => {
+ variadic_error(tcx.sess, arg.span, arg_ty, "c_int");
+ }
+ ty::Uint(ty::UintTy::U8 | ty::UintTy::U16) => {
+ variadic_error(tcx.sess, arg.span, arg_ty, "c_uint");
+ }
+ ty::FnDef(..) => {
+ let ptr_ty = self.tcx.mk_fn_ptr(arg_ty.fn_sig(self.tcx));
+ let ptr_ty = self.resolve_vars_if_possible(ptr_ty);
+ variadic_error(tcx.sess, arg.span, arg_ty, &ptr_ty.to_string());
+ }
+ _ => {}
+ }
+ }
+ }
+
+ if !call_appears_satisfied {
+ let compatibility_diagonal = IndexVec::from_raw(compatibility_diagonal);
+ let provided_args = IndexVec::from_iter(provided_args.iter().take(if c_variadic {
+ minimum_input_count
+ } else {
+ provided_arg_count
+ }));
+ debug_assert_eq!(
+ formal_input_tys.len(),
+ expected_input_tys.len(),
+ "expected formal_input_tys to be the same size as expected_input_tys"
+ );
+ let formal_and_expected_inputs = IndexVec::from_iter(
+ formal_input_tys
+ .iter()
+ .copied()
+ .zip(expected_input_tys.iter().copied())
+ .map(|vars| self.resolve_vars_if_possible(vars)),
+ );
+
+ self.report_arg_errors(
+ compatibility_diagonal,
+ formal_and_expected_inputs,
+ provided_args,
+ c_variadic,
+ err_code,
+ fn_def_id,
+ call_span,
+ call_expr,
+ );
+ }
+ }
+
+ fn report_arg_errors(
+ &self,
+ compatibility_diagonal: IndexVec<ProvidedIdx, Compatibility<'tcx>>,
+ formal_and_expected_inputs: IndexVec<ExpectedIdx, (Ty<'tcx>, Ty<'tcx>)>,
+ provided_args: IndexVec<ProvidedIdx, &'tcx hir::Expr<'tcx>>,
+ c_variadic: bool,
+ err_code: &str,
+ fn_def_id: Option<DefId>,
+ call_span: Span,
+ call_expr: &hir::Expr<'tcx>,
+ ) {
+ // Next, let's construct the error
+ let (error_span, full_call_span, ctor_of, is_method) = match &call_expr.kind {
+ hir::ExprKind::Call(
+ hir::Expr { hir_id, span, kind: hir::ExprKind::Path(qpath), .. },
+ _,
+ ) => {
+ if let Res::Def(DefKind::Ctor(of, _), _) =
+ self.typeck_results.borrow().qpath_res(qpath, *hir_id)
+ {
+ (call_span, *span, Some(of), false)
+ } else {
+ (call_span, *span, None, false)
+ }
+ }
+ hir::ExprKind::Call(hir::Expr { span, .. }, _) => (call_span, *span, None, false),
+ hir::ExprKind::MethodCall(path_segment, _, _, span) => {
+ let ident_span = path_segment.ident.span;
+ let ident_span = if let Some(args) = path_segment.args {
+ ident_span.with_hi(args.span_ext.hi())
+ } else {
+ ident_span
+ };
+ // methods are never ctors
+ (*span, ident_span, None, true)
+ }
+ k => span_bug!(call_span, "checking argument types on a non-call: `{:?}`", k),
+ };
+ let args_span = error_span.trim_start(full_call_span).unwrap_or(error_span);
+ let call_name = match ctor_of {
+ Some(CtorOf::Struct) => "struct",
+ Some(CtorOf::Variant) => "enum variant",
+ None => "function",
+ };
+
+ // Don't print if it has error types or is just plain `_`
+ fn has_error_or_infer<'tcx>(tys: impl IntoIterator<Item = Ty<'tcx>>) -> bool {
+ tys.into_iter().any(|ty| ty.references_error() || ty.is_ty_var())
+ }
+
+ self.set_tainted_by_errors();
+ let tcx = self.tcx;
+
+ // Get the argument span in the context of the call span so that
+ // suggestions and labels are (more) correct when an arg is a
+ // macro invocation.
+ let normalize_span = |span: Span| -> Span {
+ let normalized_span = span.find_ancestor_inside(error_span).unwrap_or(span);
+ // Sometimes macros mess up the spans, so do not normalize the
+ // arg span to equal the error span, because that's less useful
+ // than pointing out the arg expr in the wrong context.
+ if normalized_span.source_equal(error_span) { span } else { normalized_span }
+ };
+
+ // Precompute the provided types and spans, since that's all we typically need for below
+ let provided_arg_tys: IndexVec<ProvidedIdx, (Ty<'tcx>, Span)> = provided_args
+ .iter()
+ .map(|expr| {
+ let ty = self
+ .typeck_results
+ .borrow()
+ .expr_ty_adjusted_opt(*expr)
+ .unwrap_or_else(|| tcx.ty_error());
+ (self.resolve_vars_if_possible(ty), normalize_span(expr.span))
+ })
+ .collect();
+ let callee_expr = match &call_expr.peel_blocks().kind {
+ hir::ExprKind::Call(callee, _) => Some(*callee),
+ hir::ExprKind::MethodCall(_, receiver, ..) => {
+ if let Some((DefKind::AssocFn, def_id)) =
+ self.typeck_results.borrow().type_dependent_def(call_expr.hir_id)
+ && let Some(assoc) = tcx.opt_associated_item(def_id)
+ && assoc.fn_has_self_parameter
+ {
+ Some(*receiver)
+ } else {
+ None
+ }
+ }
+ _ => None,
+ };
+ let callee_ty = callee_expr
+ .and_then(|callee_expr| self.typeck_results.borrow().expr_ty_adjusted_opt(callee_expr));
+
+ // A "softer" version of the `demand_compatible`, which checks types without persisting them,
+ // and treats error types differently
+ // This will allow us to "probe" for other argument orders that would likely have been correct
+ let check_compatible = |provided_idx: ProvidedIdx, expected_idx: ExpectedIdx| {
+ if provided_idx.as_usize() == expected_idx.as_usize() {
+ return compatibility_diagonal[provided_idx].clone();
+ }
+
+ let (formal_input_ty, expected_input_ty) = formal_and_expected_inputs[expected_idx];
+ // If either is an error type, we defy the usual convention and consider them to *not* be
+ // coercible. This prevents our error message heuristic from trying to pass errors into
+ // every argument.
+ if (formal_input_ty, expected_input_ty).references_error() {
+ return Compatibility::Incompatible(None);
+ }
+
+ let (arg_ty, arg_span) = provided_arg_tys[provided_idx];
+
+ let expectation = Expectation::rvalue_hint(self, expected_input_ty);
+ let coerced_ty = expectation.only_has_type(self).unwrap_or(formal_input_ty);
+ let can_coerce = self.can_coerce(arg_ty, coerced_ty);
+ if !can_coerce {
+ return Compatibility::Incompatible(Some(ty::error::TypeError::Sorts(
+ ty::error::ExpectedFound::new(true, coerced_ty, arg_ty),
+ )));
+ }
+
+ // Using probe here, since we don't want this subtyping to affect inference.
+ let subtyping_error = self.probe(|_| {
+ self.at(&self.misc(arg_span), self.param_env).sup(formal_input_ty, coerced_ty).err()
+ });
+
+ // Same as above: if either the coerce type or the checked type is an error type,
+ // consider them *not* compatible.
+ let references_error = (coerced_ty, arg_ty).references_error();
+ match (references_error, subtyping_error) {
+ (false, None) => Compatibility::Compatible,
+ (_, subtyping_error) => Compatibility::Incompatible(subtyping_error),
+ }
+ };
+
+ // The algorithm here is inspired by levenshtein distance and longest common subsequence.
+ // We'll try to detect 4 different types of mistakes:
+ // - An extra parameter has been provided that doesn't satisfy *any* of the other inputs
+ // - An input is missing, which isn't satisfied by *any* of the other arguments
+ // - Some number of arguments have been provided in the wrong order
+ // - A type is straight up invalid
+
+ // First, let's find the errors
+ let (mut errors, matched_inputs) =
+ ArgMatrix::new(provided_args.len(), formal_and_expected_inputs.len(), check_compatible)
+ .find_errors();
+
+ // First, check if we just need to wrap some arguments in a tuple.
+ if let Some((mismatch_idx, terr)) =
+ compatibility_diagonal.iter().enumerate().find_map(|(i, c)| {
+ if let Compatibility::Incompatible(Some(terr)) = c {
+ Some((i, *terr))
+ } else {
+ None
+ }
+ })
+ {
+ // Is the first bad expected argument a tuple?
+ // Do we have as many extra provided arguments as the tuple's length?
+ // If so, we might have just forgotten to wrap some args in a tuple.
+ if let Some(ty::Tuple(tys)) =
+ formal_and_expected_inputs.get(mismatch_idx.into()).map(|tys| tys.1.kind())
+ // If the tuple is unit, we're not actually wrapping any arguments.
+ && !tys.is_empty()
+ && provided_arg_tys.len() == formal_and_expected_inputs.len() - 1 + tys.len()
+ {
+ // Wrap up the N provided arguments starting at this position in a tuple.
+ let provided_as_tuple = tcx.mk_tup(
+ provided_arg_tys.iter().map(|(ty, _)| *ty).skip(mismatch_idx).take(tys.len()),
+ );
+
+ let mut satisfied = true;
+ // Check if the newly wrapped tuple + rest of the arguments are compatible.
+ for ((_, expected_ty), provided_ty) in std::iter::zip(
+ formal_and_expected_inputs.iter().skip(mismatch_idx),
+ [provided_as_tuple].into_iter().chain(
+ provided_arg_tys.iter().map(|(ty, _)| *ty).skip(mismatch_idx + tys.len()),
+ ),
+ ) {
+ if !self.can_coerce(provided_ty, *expected_ty) {
+ satisfied = false;
+ break;
+ }
+ }
+
+ // If they're compatible, suggest wrapping in an arg, and we're done!
+ // Take some care with spans, so we don't suggest wrapping a macro's
+ // innards in parenthesis, for example.
+ if satisfied
+ && let Some((_, lo)) =
+ provided_arg_tys.get(ProvidedIdx::from_usize(mismatch_idx))
+ && let Some((_, hi)) =
+ provided_arg_tys.get(ProvidedIdx::from_usize(mismatch_idx + tys.len() - 1))
+ {
+ let mut err;
+ if tys.len() == 1 {
+ // A tuple wrap suggestion actually occurs within,
+ // so don't do anything special here.
+ err = self.err_ctxt().report_and_explain_type_error(
+ TypeTrace::types(
+ &self.misc(*lo),
+ true,
+ formal_and_expected_inputs[mismatch_idx.into()].1,
+ provided_arg_tys[mismatch_idx.into()].0,
+ ),
+ terr,
+ );
+ err.span_label(
+ full_call_span,
+ format!("arguments to this {} are incorrect", call_name),
+ );
+ } else {
+ err = tcx.sess.struct_span_err_with_code(
+ full_call_span,
+ &format!(
+ "this {} takes {}{} but {} {} supplied",
+ call_name,
+ if c_variadic { "at least " } else { "" },
+ potentially_plural_count(
+ formal_and_expected_inputs.len(),
+ "argument"
+ ),
+ potentially_plural_count(provided_args.len(), "argument"),
+ pluralize!("was", provided_args.len())
+ ),
+ DiagnosticId::Error(err_code.to_owned()),
+ );
+ err.multipart_suggestion_verbose(
+ "wrap these arguments in parentheses to construct a tuple",
+ vec![
+ (lo.shrink_to_lo(), "(".to_string()),
+ (hi.shrink_to_hi(), ")".to_string()),
+ ],
+ Applicability::MachineApplicable,
+ );
+ };
+ self.label_fn_like(
+ &mut err,
+ fn_def_id,
+ callee_ty,
+ Some(mismatch_idx),
+ is_method,
+ );
+ err.emit();
+ return;
+ }
+ }
+ }
+
+ // Okay, so here's where it gets complicated in regards to what errors
+ // we emit and how.
+ // There are 3 different "types" of errors we might encounter.
+ // 1) Missing/extra/swapped arguments
+ // 2) Valid but incorrect arguments
+ // 3) Invalid arguments
+ // - Currently I think this only comes up with `CyclicTy`
+ //
+ // We first need to go through, remove those from (3) and emit those
+ // as their own error, particularly since they're error code and
+ // message is special. From what I can tell, we *must* emit these
+ // here (vs somewhere prior to this function) since the arguments
+ // become invalid *because* of how they get used in the function.
+ // It is what it is.
+
+ if errors.is_empty() {
+ if cfg!(debug_assertions) {
+ span_bug!(error_span, "expected errors from argument matrix");
+ } else {
+ tcx.sess
+ .struct_span_err(
+ error_span,
+ "argument type mismatch was detected, \
+ but rustc had trouble determining where",
+ )
+ .note(
+ "we would appreciate a bug report: \
+ https://github.com/rust-lang/rust/issues/new",
+ )
+ .emit();
+ }
+ return;
+ }
+
+ errors.drain_filter(|error| {
+ let Error::Invalid(provided_idx, expected_idx, Compatibility::Incompatible(Some(e))) = error else { return false };
+ let (provided_ty, provided_span) = provided_arg_tys[*provided_idx];
+ let (expected_ty, _) = formal_and_expected_inputs[*expected_idx];
+ let cause = &self.misc(provided_span);
+ let trace = TypeTrace::types(cause, true, expected_ty, provided_ty);
+ if !matches!(trace.cause.as_failure_code(*e), FailureCode::Error0308(_)) {
+ self.err_ctxt().report_and_explain_type_error(trace, *e).emit();
+ return true;
+ }
+ false
+ });
+
+ // We're done if we found errors, but we already emitted them.
+ if errors.is_empty() {
+ return;
+ }
+
+ // Okay, now that we've emitted the special errors separately, we
+ // are only left missing/extra/swapped and mismatched arguments, both
+ // can be collated pretty easily if needed.
+
+ // Next special case: if there is only one "Incompatible" error, just emit that
+ if let [
+ Error::Invalid(provided_idx, expected_idx, Compatibility::Incompatible(Some(err))),
+ ] = &errors[..]
+ {
+ let (formal_ty, expected_ty) = formal_and_expected_inputs[*expected_idx];
+ let (provided_ty, provided_arg_span) = provided_arg_tys[*provided_idx];
+ let cause = &self.misc(provided_arg_span);
+ let trace = TypeTrace::types(cause, true, expected_ty, provided_ty);
+ let mut err = self.err_ctxt().report_and_explain_type_error(trace, *err);
+ self.emit_coerce_suggestions(
+ &mut err,
+ &provided_args[*provided_idx],
+ provided_ty,
+ Expectation::rvalue_hint(self, expected_ty)
+ .only_has_type(self)
+ .unwrap_or(formal_ty),
+ None,
+ None,
+ );
+ err.span_label(
+ full_call_span,
+ format!("arguments to this {} are incorrect", call_name),
+ );
+ // Call out where the function is defined
+ self.label_fn_like(
+ &mut err,
+ fn_def_id,
+ callee_ty,
+ Some(expected_idx.as_usize()),
+ is_method,
+ );
+ err.emit();
+ return;
+ }
+
+ let mut err = if formal_and_expected_inputs.len() == provided_args.len() {
+ struct_span_err!(
+ tcx.sess,
+ full_call_span,
+ E0308,
+ "arguments to this {} are incorrect",
+ call_name,
+ )
+ } else {
+ tcx.sess.struct_span_err_with_code(
+ full_call_span,
+ &format!(
+ "this {} takes {}{} but {} {} supplied",
+ call_name,
+ if c_variadic { "at least " } else { "" },
+ potentially_plural_count(formal_and_expected_inputs.len(), "argument"),
+ potentially_plural_count(provided_args.len(), "argument"),
+ pluralize!("was", provided_args.len())
+ ),
+ DiagnosticId::Error(err_code.to_owned()),
+ )
+ };
+
+ // As we encounter issues, keep track of what we want to provide for the suggestion
+ let mut labels = vec![];
+ // If there is a single error, we give a specific suggestion; otherwise, we change to
+ // "did you mean" with the suggested function call
+ enum SuggestionText {
+ None,
+ Provide(bool),
+ Remove(bool),
+ Swap,
+ Reorder,
+ DidYouMean,
+ }
+ let mut suggestion_text = SuggestionText::None;
+
+ let mut errors = errors.into_iter().peekable();
+ while let Some(error) = errors.next() {
+ match error {
+ Error::Invalid(provided_idx, expected_idx, compatibility) => {
+ let (formal_ty, expected_ty) = formal_and_expected_inputs[expected_idx];
+ let (provided_ty, provided_span) = provided_arg_tys[provided_idx];
+ if let Compatibility::Incompatible(error) = compatibility {
+ let cause = &self.misc(provided_span);
+ let trace = TypeTrace::types(cause, true, expected_ty, provided_ty);
+ if let Some(e) = error {
+ self.err_ctxt().note_type_err(
+ &mut err,
+ &trace.cause,
+ None,
+ Some(trace.values),
+ e,
+ false,
+ true,
+ );
+ }
+ }
+
+ self.emit_coerce_suggestions(
+ &mut err,
+ &provided_args[provided_idx],
+ provided_ty,
+ Expectation::rvalue_hint(self, expected_ty)
+ .only_has_type(self)
+ .unwrap_or(formal_ty),
+ None,
+ None,
+ );
+ }
+ Error::Extra(arg_idx) => {
+ let (provided_ty, provided_span) = provided_arg_tys[arg_idx];
+ let provided_ty_name = if !has_error_or_infer([provided_ty]) {
+ // FIXME: not suggestable, use something else
+ format!(" of type `{}`", provided_ty)
+ } else {
+ "".to_string()
+ };
+ labels
+ .push((provided_span, format!("argument{} unexpected", provided_ty_name)));
+ suggestion_text = match suggestion_text {
+ SuggestionText::None => SuggestionText::Remove(false),
+ SuggestionText::Remove(_) => SuggestionText::Remove(true),
+ _ => SuggestionText::DidYouMean,
+ };
+ }
+ Error::Missing(expected_idx) => {
+ // If there are multiple missing arguments adjacent to each other,
+ // then we can provide a single error.
+
+ let mut missing_idxs = vec![expected_idx];
+ while let Some(e) = errors.next_if(|e| {
+ matches!(e, Error::Missing(next_expected_idx)
+ if *next_expected_idx == *missing_idxs.last().unwrap() + 1)
+ }) {
+ match e {
+ Error::Missing(expected_idx) => missing_idxs.push(expected_idx),
+ _ => unreachable!(),
+ }
+ }
+
+ // NOTE: Because we might be re-arranging arguments, might have extra
+ // arguments, etc. it's hard to *really* know where we should provide
+ // this error label, so as a heuristic, we point to the provided arg, or
+ // to the call if the missing inputs pass the provided args.
+ match &missing_idxs[..] {
+ &[expected_idx] => {
+ let (_, input_ty) = formal_and_expected_inputs[expected_idx];
+ let span = if let Some((_, arg_span)) =
+ provided_arg_tys.get(expected_idx.to_provided_idx())
+ {
+ *arg_span
+ } else {
+ args_span
+ };
+ let rendered = if !has_error_or_infer([input_ty]) {
+ format!(" of type `{}`", input_ty)
+ } else {
+ "".to_string()
+ };
+ labels.push((span, format!("an argument{} is missing", rendered)));
+ suggestion_text = match suggestion_text {
+ SuggestionText::None => SuggestionText::Provide(false),
+ SuggestionText::Provide(_) => SuggestionText::Provide(true),
+ _ => SuggestionText::DidYouMean,
+ };
+ }
+ &[first_idx, second_idx] => {
+ let (_, first_expected_ty) = formal_and_expected_inputs[first_idx];
+ let (_, second_expected_ty) = formal_and_expected_inputs[second_idx];
+ let span = if let (Some((_, first_span)), Some((_, second_span))) = (
+ provided_arg_tys.get(first_idx.to_provided_idx()),
+ provided_arg_tys.get(second_idx.to_provided_idx()),
+ ) {
+ first_span.to(*second_span)
+ } else {
+ args_span
+ };
+ let rendered =
+ if !has_error_or_infer([first_expected_ty, second_expected_ty]) {
+ format!(
+ " of type `{}` and `{}`",
+ first_expected_ty, second_expected_ty
+ )
+ } else {
+ "".to_string()
+ };
+ labels.push((span, format!("two arguments{} are missing", rendered)));
+ suggestion_text = match suggestion_text {
+ SuggestionText::None | SuggestionText::Provide(_) => {
+ SuggestionText::Provide(true)
+ }
+ _ => SuggestionText::DidYouMean,
+ };
+ }
+ &[first_idx, second_idx, third_idx] => {
+ let (_, first_expected_ty) = formal_and_expected_inputs[first_idx];
+ let (_, second_expected_ty) = formal_and_expected_inputs[second_idx];
+ let (_, third_expected_ty) = formal_and_expected_inputs[third_idx];
+ let span = if let (Some((_, first_span)), Some((_, third_span))) = (
+ provided_arg_tys.get(first_idx.to_provided_idx()),
+ provided_arg_tys.get(third_idx.to_provided_idx()),
+ ) {
+ first_span.to(*third_span)
+ } else {
+ args_span
+ };
+ let rendered = if !has_error_or_infer([
+ first_expected_ty,
+ second_expected_ty,
+ third_expected_ty,
+ ]) {
+ format!(
+ " of type `{}`, `{}`, and `{}`",
+ first_expected_ty, second_expected_ty, third_expected_ty
+ )
+ } else {
+ "".to_string()
+ };
+ labels.push((span, format!("three arguments{} are missing", rendered)));
+ suggestion_text = match suggestion_text {
+ SuggestionText::None | SuggestionText::Provide(_) => {
+ SuggestionText::Provide(true)
+ }
+ _ => SuggestionText::DidYouMean,
+ };
+ }
+ missing_idxs => {
+ let first_idx = *missing_idxs.first().unwrap();
+ let last_idx = *missing_idxs.last().unwrap();
+ // NOTE: Because we might be re-arranging arguments, might have extra arguments, etc.
+ // It's hard to *really* know where we should provide this error label, so this is a
+ // decent heuristic
+ let span = if let (Some((_, first_span)), Some((_, last_span))) = (
+ provided_arg_tys.get(first_idx.to_provided_idx()),
+ provided_arg_tys.get(last_idx.to_provided_idx()),
+ ) {
+ first_span.to(*last_span)
+ } else {
+ args_span
+ };
+ labels.push((span, format!("multiple arguments are missing")));
+ suggestion_text = match suggestion_text {
+ SuggestionText::None | SuggestionText::Provide(_) => {
+ SuggestionText::Provide(true)
+ }
+ _ => SuggestionText::DidYouMean,
+ };
+ }
+ }
+ }
+ Error::Swap(
+ first_provided_idx,
+ second_provided_idx,
+ first_expected_idx,
+ second_expected_idx,
+ ) => {
+ let (first_provided_ty, first_span) = provided_arg_tys[first_provided_idx];
+ let (_, first_expected_ty) = formal_and_expected_inputs[first_expected_idx];
+ let first_provided_ty_name = if !has_error_or_infer([first_provided_ty]) {
+ format!(", found `{}`", first_provided_ty)
+ } else {
+ String::new()
+ };
+ labels.push((
+ first_span,
+ format!("expected `{}`{}", first_expected_ty, first_provided_ty_name),
+ ));
+
+ let (second_provided_ty, second_span) = provided_arg_tys[second_provided_idx];
+ let (_, second_expected_ty) = formal_and_expected_inputs[second_expected_idx];
+ let second_provided_ty_name = if !has_error_or_infer([second_provided_ty]) {
+ format!(", found `{}`", second_provided_ty)
+ } else {
+ String::new()
+ };
+ labels.push((
+ second_span,
+ format!("expected `{}`{}", second_expected_ty, second_provided_ty_name),
+ ));
+
+ suggestion_text = match suggestion_text {
+ SuggestionText::None => SuggestionText::Swap,
+ _ => SuggestionText::DidYouMean,
+ };
+ }
+ Error::Permutation(args) => {
+ for (dst_arg, dest_input) in args {
+ let (_, expected_ty) = formal_and_expected_inputs[dst_arg];
+ let (provided_ty, provided_span) = provided_arg_tys[dest_input];
+ let provided_ty_name = if !has_error_or_infer([provided_ty]) {
+ format!(", found `{}`", provided_ty)
+ } else {
+ String::new()
+ };
+ labels.push((
+ provided_span,
+ format!("expected `{}`{}", expected_ty, provided_ty_name),
+ ));
+ }
+
+ suggestion_text = match suggestion_text {
+ SuggestionText::None => SuggestionText::Reorder,
+ _ => SuggestionText::DidYouMean,
+ };
+ }
+ }
+ }
+
+ // If we have less than 5 things to say, it would be useful to call out exactly what's wrong
+ if labels.len() <= 5 {
+ for (span, label) in labels {
+ err.span_label(span, label);
+ }
+ }
+
+ // Call out where the function is defined
+ self.label_fn_like(&mut err, fn_def_id, callee_ty, None, is_method);
+
+ // And add a suggestion block for all of the parameters
+ let suggestion_text = match suggestion_text {
+ SuggestionText::None => None,
+ SuggestionText::Provide(plural) => {
+ Some(format!("provide the argument{}", if plural { "s" } else { "" }))
+ }
+ SuggestionText::Remove(plural) => {
+ Some(format!("remove the extra argument{}", if plural { "s" } else { "" }))
+ }
+ SuggestionText::Swap => Some("swap these arguments".to_string()),
+ SuggestionText::Reorder => Some("reorder these arguments".to_string()),
+ SuggestionText::DidYouMean => Some("did you mean".to_string()),
+ };
+ if let Some(suggestion_text) = suggestion_text {
+ let source_map = self.sess().source_map();
+ let (mut suggestion, suggestion_span) =
+ if let Some(call_span) = full_call_span.find_ancestor_inside(error_span) {
+ ("(".to_string(), call_span.shrink_to_hi().to(error_span.shrink_to_hi()))
+ } else {
+ (
+ format!(
+ "{}(",
+ source_map.span_to_snippet(full_call_span).unwrap_or_else(|_| {
+ fn_def_id.map_or("".to_string(), |fn_def_id| {
+ tcx.item_name(fn_def_id).to_string()
+ })
+ })
+ ),
+ error_span,
+ )
+ };
+ let mut needs_comma = false;
+ for (expected_idx, provided_idx) in matched_inputs.iter_enumerated() {
+ if needs_comma {
+ suggestion += ", ";
+ } else {
+ needs_comma = true;
+ }
+ let suggestion_text = if let Some(provided_idx) = provided_idx
+ && let (_, provided_span) = provided_arg_tys[*provided_idx]
+ && let Ok(arg_text) = source_map.span_to_snippet(provided_span)
+ {
+ arg_text
+ } else {
+ // Propose a placeholder of the correct type
+ let (_, expected_ty) = formal_and_expected_inputs[expected_idx];
+ if expected_ty.is_unit() {
+ "()".to_string()
+ } else if expected_ty.is_suggestable(tcx, false) {
+ format!("/* {} */", expected_ty)
+ } else {
+ "/* value */".to_string()
+ }
+ };
+ suggestion += &suggestion_text;
+ }
+ suggestion += ")";
+ err.span_suggestion_verbose(
+ suggestion_span,
+ &suggestion_text,
+ suggestion,
+ Applicability::HasPlaceholders,
+ );
+ }
+
+ err.emit();
+ }
+
+ // AST fragment checking
+ pub(in super::super) fn check_lit(
+ &self,
+ lit: &hir::Lit,
+ expected: Expectation<'tcx>,
+ ) -> Ty<'tcx> {
+ let tcx = self.tcx;
+
+ match lit.node {
+ ast::LitKind::Str(..) => tcx.mk_static_str(),
+ ast::LitKind::ByteStr(ref v) => {
+ tcx.mk_imm_ref(tcx.lifetimes.re_static, tcx.mk_array(tcx.types.u8, v.len() as u64))
+ }
+ ast::LitKind::Byte(_) => tcx.types.u8,
+ ast::LitKind::Char(_) => tcx.types.char,
+ ast::LitKind::Int(_, ast::LitIntType::Signed(t)) => tcx.mk_mach_int(ty::int_ty(t)),
+ ast::LitKind::Int(_, ast::LitIntType::Unsigned(t)) => tcx.mk_mach_uint(ty::uint_ty(t)),
+ ast::LitKind::Int(_, ast::LitIntType::Unsuffixed) => {
+ let opt_ty = expected.to_option(self).and_then(|ty| match ty.kind() {
+ ty::Int(_) | ty::Uint(_) => Some(ty),
+ ty::Char => Some(tcx.types.u8),
+ ty::RawPtr(..) => Some(tcx.types.usize),
+ ty::FnDef(..) | ty::FnPtr(_) => Some(tcx.types.usize),
+ _ => None,
+ });
+ opt_ty.unwrap_or_else(|| self.next_int_var())
+ }
+ ast::LitKind::Float(_, ast::LitFloatType::Suffixed(t)) => {
+ tcx.mk_mach_float(ty::float_ty(t))
+ }
+ ast::LitKind::Float(_, ast::LitFloatType::Unsuffixed) => {
+ let opt_ty = expected.to_option(self).and_then(|ty| match ty.kind() {
+ ty::Float(_) => Some(ty),
+ _ => None,
+ });
+ opt_ty.unwrap_or_else(|| self.next_float_var())
+ }
+ ast::LitKind::Bool(_) => tcx.types.bool,
+ ast::LitKind::Err => tcx.ty_error(),
+ }
+ }
+
+ pub fn check_struct_path(
+ &self,
+ qpath: &QPath<'_>,
+ hir_id: hir::HirId,
+ ) -> Option<(&'tcx ty::VariantDef, Ty<'tcx>)> {
+ let path_span = qpath.span();
+ let (def, ty) = self.finish_resolving_struct_path(qpath, path_span, hir_id);
+ let variant = match def {
+ Res::Err => {
+ self.set_tainted_by_errors();
+ return None;
+ }
+ Res::Def(DefKind::Variant, _) => match ty.kind() {
+ ty::Adt(adt, substs) => Some((adt.variant_of_res(def), adt.did(), substs)),
+ _ => bug!("unexpected type: {:?}", ty),
+ },
+ Res::Def(DefKind::Struct | DefKind::Union | DefKind::TyAlias | DefKind::AssocTy, _)
+ | Res::SelfTyParam { .. }
+ | Res::SelfTyAlias { .. } => match ty.kind() {
+ ty::Adt(adt, substs) if !adt.is_enum() => {
+ Some((adt.non_enum_variant(), adt.did(), substs))
+ }
+ _ => None,
+ },
+ _ => bug!("unexpected definition: {:?}", def),
+ };
+
+ if let Some((variant, did, substs)) = variant {
+ debug!("check_struct_path: did={:?} substs={:?}", did, substs);
+ self.write_user_type_annotation_from_substs(hir_id, did, substs, None);
+
+ // Check bounds on type arguments used in the path.
+ self.add_required_obligations_for_hir(path_span, did, substs, hir_id);
+
+ Some((variant, ty))
+ } else {
+ match ty.kind() {
+ ty::Error(_) => {
+ // E0071 might be caused by a spelling error, which will have
+ // already caused an error message and probably a suggestion
+ // elsewhere. Refrain from emitting more unhelpful errors here
+ // (issue #88844).
+ }
+ _ => {
+ struct_span_err!(
+ self.tcx.sess,
+ path_span,
+ E0071,
+ "expected struct, variant or union type, found {}",
+ ty.sort_string(self.tcx)
+ )
+ .span_label(path_span, "not a struct")
+ .emit();
+ }
+ }
+ None
+ }
+ }
+
+ pub fn check_decl_initializer(
+ &self,
+ hir_id: hir::HirId,
+ pat: &'tcx hir::Pat<'tcx>,
+ init: &'tcx hir::Expr<'tcx>,
+ ) -> Ty<'tcx> {
+ // FIXME(tschottdorf): `contains_explicit_ref_binding()` must be removed
+ // for #42640 (default match binding modes).
+ //
+ // See #44848.
+ let ref_bindings = pat.contains_explicit_ref_binding();
+
+ let local_ty = self.local_ty(init.span, hir_id).revealed_ty;
+ if let Some(m) = ref_bindings {
+ // Somewhat subtle: if we have a `ref` binding in the pattern,
+ // we want to avoid introducing coercions for the RHS. This is
+ // both because it helps preserve sanity and, in the case of
+ // ref mut, for soundness (issue #23116). In particular, in
+ // the latter case, we need to be clear that the type of the
+ // referent for the reference that results is *equal to* the
+ // type of the place it is referencing, and not some
+ // supertype thereof.
+ let init_ty = self.check_expr_with_needs(init, Needs::maybe_mut_place(m));
+ self.demand_eqtype(init.span, local_ty, init_ty);
+ init_ty
+ } else {
+ self.check_expr_coercable_to_type(init, local_ty, None)
+ }
+ }
+
+ pub(in super::super) fn check_decl(&self, decl: Declaration<'tcx>) {
+ // Determine and write the type which we'll check the pattern against.
+ let decl_ty = self.local_ty(decl.span, decl.hir_id).decl_ty;
+ self.write_ty(decl.hir_id, decl_ty);
+
+ // Type check the initializer.
+ if let Some(ref init) = decl.init {
+ let init_ty = self.check_decl_initializer(decl.hir_id, decl.pat, &init);
+ self.overwrite_local_ty_if_err(decl.hir_id, decl.pat, decl_ty, init_ty);
+ }
+
+ // Does the expected pattern type originate from an expression and what is the span?
+ let (origin_expr, ty_span) = match (decl.ty, decl.init) {
+ (Some(ty), _) => (false, Some(ty.span)), // Bias towards the explicit user type.
+ (_, Some(init)) => {
+ (true, Some(init.span.find_ancestor_inside(decl.span).unwrap_or(init.span)))
+ } // No explicit type; so use the scrutinee.
+ _ => (false, None), // We have `let $pat;`, so the expected type is unconstrained.
+ };
+
+ // Type check the pattern. Override if necessary to avoid knock-on errors.
+ self.check_pat_top(&decl.pat, decl_ty, ty_span, origin_expr);
+ let pat_ty = self.node_ty(decl.pat.hir_id);
+ self.overwrite_local_ty_if_err(decl.hir_id, decl.pat, decl_ty, pat_ty);
+
+ if let Some(blk) = decl.els {
+ let previous_diverges = self.diverges.get();
+ let else_ty = self.check_block_with_expected(blk, NoExpectation);
+ let cause = self.cause(blk.span, ObligationCauseCode::LetElse);
+ if let Some(mut err) =
+ self.demand_eqtype_with_origin(&cause, self.tcx.types.never, else_ty)
+ {
+ err.emit();
+ }
+ self.diverges.set(previous_diverges);
+ }
+ }
+
+ /// Type check a `let` statement.
+ pub fn check_decl_local(&self, local: &'tcx hir::Local<'tcx>) {
+ self.check_decl(local.into());
+ }
+
+ pub fn check_stmt(&self, stmt: &'tcx hir::Stmt<'tcx>, is_last: bool) {
+ // Don't do all the complex logic below for `DeclItem`.
+ match stmt.kind {
+ hir::StmtKind::Item(..) => return,
+ hir::StmtKind::Local(..) | hir::StmtKind::Expr(..) | hir::StmtKind::Semi(..) => {}
+ }
+
+ self.warn_if_unreachable(stmt.hir_id, stmt.span, "statement");
+
+ // Hide the outer diverging and `has_errors` flags.
+ let old_diverges = self.diverges.replace(Diverges::Maybe);
+ let old_has_errors = self.has_errors.replace(false);
+
+ match stmt.kind {
+ hir::StmtKind::Local(l) => {
+ self.check_decl_local(l);
+ }
+ // Ignore for now.
+ hir::StmtKind::Item(_) => {}
+ hir::StmtKind::Expr(ref expr) => {
+ // Check with expected type of `()`.
+ self.check_expr_has_type_or_error(&expr, self.tcx.mk_unit(), |err| {
+ if expr.can_have_side_effects() {
+ self.suggest_semicolon_at_end(expr.span, err);
+ }
+ });
+ }
+ hir::StmtKind::Semi(ref expr) => {
+ // All of this is equivalent to calling `check_expr`, but it is inlined out here
+ // in order to capture the fact that this `match` is the last statement in its
+ // function. This is done for better suggestions to remove the `;`.
+ let expectation = match expr.kind {
+ hir::ExprKind::Match(..) if is_last => IsLast(stmt.span),
+ _ => NoExpectation,
+ };
+ self.check_expr_with_expectation(expr, expectation);
+ }
+ }
+
+ // Combine the diverging and `has_error` flags.
+ self.diverges.set(self.diverges.get() | old_diverges);
+ self.has_errors.set(self.has_errors.get() | old_has_errors);
+ }
+
+ pub fn check_block_no_value(&self, blk: &'tcx hir::Block<'tcx>) {
+ let unit = self.tcx.mk_unit();
+ let ty = self.check_block_with_expected(blk, ExpectHasType(unit));
+
+ // if the block produces a `!` value, that can always be
+ // (effectively) coerced to unit.
+ if !ty.is_never() {
+ self.demand_suptype(blk.span, unit, ty);
+ }
+ }
+
+ pub(in super::super) fn check_block_with_expected(
+ &self,
+ blk: &'tcx hir::Block<'tcx>,
+ expected: Expectation<'tcx>,
+ ) -> Ty<'tcx> {
+ let prev = self.ps.replace(self.ps.get().recurse(blk));
+
+ // In some cases, blocks have just one exit, but other blocks
+ // can be targeted by multiple breaks. This can happen both
+ // with labeled blocks as well as when we desugar
+ // a `try { ... }` expression.
+ //
+ // Example 1:
+ //
+ // 'a: { if true { break 'a Err(()); } Ok(()) }
+ //
+ // Here we would wind up with two coercions, one from
+ // `Err(())` and the other from the tail expression
+ // `Ok(())`. If the tail expression is omitted, that's a
+ // "forced unit" -- unless the block diverges, in which
+ // case we can ignore the tail expression (e.g., `'a: {
+ // break 'a 22; }` would not force the type of the block
+ // to be `()`).
+ let tail_expr = blk.expr.as_ref();
+ let coerce_to_ty = expected.coercion_target_type(self, blk.span);
+ let coerce = if blk.targeted_by_break {
+ CoerceMany::new(coerce_to_ty)
+ } else {
+ let tail_expr: &[&hir::Expr<'_>] = match tail_expr {
+ Some(e) => slice::from_ref(e),
+ None => &[],
+ };
+ CoerceMany::with_coercion_sites(coerce_to_ty, tail_expr)
+ };
+
+ let prev_diverges = self.diverges.get();
+ let ctxt = BreakableCtxt { coerce: Some(coerce), may_break: false };
+
+ let (ctxt, ()) = self.with_breakable_ctxt(blk.hir_id, ctxt, || {
+ for (pos, s) in blk.stmts.iter().enumerate() {
+ self.check_stmt(s, blk.stmts.len() - 1 == pos);
+ }
+
+ // check the tail expression **without** holding the
+ // `enclosing_breakables` lock below.
+ let tail_expr_ty = tail_expr.map(|t| self.check_expr_with_expectation(t, expected));
+
+ let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
+ let ctxt = enclosing_breakables.find_breakable(blk.hir_id);
+ let coerce = ctxt.coerce.as_mut().unwrap();
+ if let Some(tail_expr_ty) = tail_expr_ty {
+ let tail_expr = tail_expr.unwrap();
+ let span = self.get_expr_coercion_span(tail_expr);
+ let cause = self.cause(span, ObligationCauseCode::BlockTailExpression(blk.hir_id));
+ let ty_for_diagnostic = coerce.merged_ty();
+ // We use coerce_inner here because we want to augment the error
+ // suggesting to wrap the block in square brackets if it might've
+ // been mistaken array syntax
+ coerce.coerce_inner(
+ self,
+ &cause,
+ Some(tail_expr),
+ tail_expr_ty,
+ Some(&mut |diag: &mut Diagnostic| {
+ self.suggest_block_to_brackets(diag, blk, tail_expr_ty, ty_for_diagnostic);
+ }),
+ false,
+ );
+ } else {
+ // Subtle: if there is no explicit tail expression,
+ // that is typically equivalent to a tail expression
+ // of `()` -- except if the block diverges. In that
+ // case, there is no value supplied from the tail
+ // expression (assuming there are no other breaks,
+ // this implies that the type of the block will be
+ // `!`).
+ //
+ // #41425 -- label the implicit `()` as being the
+ // "found type" here, rather than the "expected type".
+ if !self.diverges.get().is_always() {
+ // #50009 -- Do not point at the entire fn block span, point at the return type
+ // span, as it is the cause of the requirement, and
+ // `consider_hint_about_removing_semicolon` will point at the last expression
+ // if it were a relevant part of the error. This improves usability in editors
+ // that highlight errors inline.
+ let mut sp = blk.span;
+ let mut fn_span = None;
+ if let Some((decl, ident)) = self.get_parent_fn_decl(blk.hir_id) {
+ let ret_sp = decl.output.span();
+ if let Some(block_sp) = self.parent_item_span(blk.hir_id) {
+ // HACK: on some cases (`ui/liveness/liveness-issue-2163.rs`) the
+ // output would otherwise be incorrect and even misleading. Make sure
+ // the span we're aiming at correspond to a `fn` body.
+ if block_sp == blk.span {
+ sp = ret_sp;
+ fn_span = Some(ident.span);
+ }
+ }
+ }
+ coerce.coerce_forced_unit(
+ self,
+ &self.misc(sp),
+ &mut |err| {
+ if let Some(expected_ty) = expected.only_has_type(self) {
+ if !self.consider_removing_semicolon(blk, expected_ty, err) {
+ self.err_ctxt().consider_returning_binding(
+ blk,
+ expected_ty,
+ err,
+ );
+ }
+ if expected_ty == self.tcx.types.bool {
+ // If this is caused by a missing `let` in a `while let`,
+ // silence this redundant error, as we already emit E0070.
+
+ // Our block must be a `assign desugar local; assignment`
+ if let Some(hir::Node::Block(hir::Block {
+ stmts:
+ [
+ hir::Stmt {
+ kind:
+ hir::StmtKind::Local(hir::Local {
+ source:
+ hir::LocalSource::AssignDesugar(_),
+ ..
+ }),
+ ..
+ },
+ hir::Stmt {
+ kind:
+ hir::StmtKind::Expr(hir::Expr {
+ kind: hir::ExprKind::Assign(..),
+ ..
+ }),
+ ..
+ },
+ ],
+ ..
+ })) = self.tcx.hir().find(blk.hir_id)
+ {
+ self.comes_from_while_condition(blk.hir_id, |_| {
+ err.downgrade_to_delayed_bug();
+ })
+ }
+ }
+ }
+ if let Some(fn_span) = fn_span {
+ err.span_label(
+ fn_span,
+ "implicitly returns `()` as its body has no tail or `return` \
+ expression",
+ );
+ }
+ },
+ false,
+ );
+ }
+ }
+ });
+
+ if ctxt.may_break {
+ // If we can break from the block, then the block's exit is always reachable
+ // (... as long as the entry is reachable) - regardless of the tail of the block.
+ self.diverges.set(prev_diverges);
+ }
+
+ let mut ty = ctxt.coerce.unwrap().complete(self);
+
+ if self.has_errors.get() || ty.references_error() {
+ ty = self.tcx.ty_error()
+ }
+
+ self.write_ty(blk.hir_id, ty);
+
+ self.ps.set(prev);
+ ty
+ }
+
+ fn parent_item_span(&self, id: hir::HirId) -> Option<Span> {
+ let node = self.tcx.hir().get_by_def_id(self.tcx.hir().get_parent_item(id).def_id);
+ match node {
+ Node::Item(&hir::Item { kind: hir::ItemKind::Fn(_, _, body_id), .. })
+ | Node::ImplItem(&hir::ImplItem { kind: hir::ImplItemKind::Fn(_, body_id), .. }) => {
+ let body = self.tcx.hir().body(body_id);
+ if let ExprKind::Block(block, _) = &body.value.kind {
+ return Some(block.span);
+ }
+ }
+ _ => {}
+ }
+ None
+ }
+
+ /// Given a function block's `HirId`, returns its `FnDecl` if it exists, or `None` otherwise.
+ fn get_parent_fn_decl(&self, blk_id: hir::HirId) -> Option<(&'tcx hir::FnDecl<'tcx>, Ident)> {
+ let parent = self.tcx.hir().get_by_def_id(self.tcx.hir().get_parent_item(blk_id).def_id);
+ self.get_node_fn_decl(parent).map(|(fn_decl, ident, _)| (fn_decl, ident))
+ }
+
+ /// If `expr` is a `match` expression that has only one non-`!` arm, use that arm's tail
+ /// expression's `Span`, otherwise return `expr.span`. This is done to give better errors
+ /// when given code like the following:
+ /// ```text
+ /// if false { return 0i32; } else { 1u32 }
+ /// // ^^^^ point at this instead of the whole `if` expression
+ /// ```
+ fn get_expr_coercion_span(&self, expr: &hir::Expr<'_>) -> rustc_span::Span {
+ let check_in_progress = |elem: &hir::Expr<'_>| {
+ self.typeck_results.borrow().node_type_opt(elem.hir_id).filter(|ty| !ty.is_never()).map(
+ |_| match elem.kind {
+ // Point at the tail expression when possible.
+ hir::ExprKind::Block(block, _) => block.expr.map_or(block.span, |e| e.span),
+ _ => elem.span,
+ },
+ )
+ };
+
+ if let hir::ExprKind::If(_, _, Some(el)) = expr.kind {
+ if let Some(rslt) = check_in_progress(el) {
+ return rslt;
+ }
+ }
+
+ if let hir::ExprKind::Match(_, arms, _) = expr.kind {
+ let mut iter = arms.iter().filter_map(|arm| check_in_progress(arm.body));
+ if let Some(span) = iter.next() {
+ if iter.next().is_none() {
+ return span;
+ }
+ }
+ }
+
+ expr.span
+ }
+
+ fn overwrite_local_ty_if_err(
+ &self,
+ hir_id: hir::HirId,
+ pat: &'tcx hir::Pat<'tcx>,
+ decl_ty: Ty<'tcx>,
+ ty: Ty<'tcx>,
+ ) {
+ if ty.references_error() {
+ // Override the types everywhere with `err()` to avoid knock on errors.
+ self.write_ty(hir_id, ty);
+ self.write_ty(pat.hir_id, ty);
+ let local_ty = LocalTy { decl_ty, revealed_ty: ty };
+ self.locals.borrow_mut().insert(hir_id, local_ty);
+ self.locals.borrow_mut().insert(pat.hir_id, local_ty);
+ }
+ }
+
+ // Finish resolving a path in a struct expression or pattern `S::A { .. }` if necessary.
+ // The newly resolved definition is written into `type_dependent_defs`.
+ fn finish_resolving_struct_path(
+ &self,
+ qpath: &QPath<'_>,
+ path_span: Span,
+ hir_id: hir::HirId,
+ ) -> (Res, Ty<'tcx>) {
+ match *qpath {
+ QPath::Resolved(ref maybe_qself, ref path) => {
+ let self_ty = maybe_qself.as_ref().map(|qself| self.to_ty(qself));
+ let ty = <dyn AstConv<'_>>::res_to_ty(self, self_ty, path, true);
+ (path.res, ty)
+ }
+ QPath::TypeRelative(ref qself, ref segment) => {
+ let ty = self.to_ty(qself);
+
+ let result = <dyn AstConv<'_>>::associated_path_to_ty(
+ self, hir_id, path_span, ty, qself, segment, true,
+ );
+ let ty = result.map(|(ty, _, _)| ty).unwrap_or_else(|_| self.tcx().ty_error());
+ let result = result.map(|(_, kind, def_id)| (kind, def_id));
+
+ // Write back the new resolution.
+ self.write_resolution(hir_id, result);
+
+ (result.map_or(Res::Err, |(kind, def_id)| Res::Def(kind, def_id)), ty)
+ }
+ QPath::LangItem(lang_item, span, id) => {
+ self.resolve_lang_item_path(lang_item, span, hir_id, id)
+ }
+ }
+ }
+
+ /// Given a vector of fulfillment errors, try to adjust the spans of the
+ /// errors to more accurately point at the cause of the failure.
+ ///
+ /// This applies to calls, methods, and struct expressions. This will also
+ /// try to deduplicate errors that are due to the same cause but might
+ /// have been created with different [`ObligationCause`][traits::ObligationCause]s.
+ pub(super) fn adjust_fulfillment_errors_for_expr_obligation(
+ &self,
+ errors: &mut Vec<traits::FulfillmentError<'tcx>>,
+ ) {
+ // Store a mapping from `(Span, Predicate) -> ObligationCause`, so that
+ // other errors that have the same span and predicate can also get fixed,
+ // even if their `ObligationCauseCode` isn't an `Expr*Obligation` kind.
+ // This is important since if we adjust one span but not the other, then
+ // we will have "duplicated" the error on the UI side.
+ let mut remap_cause = FxHashSet::default();
+ let mut not_adjusted = vec![];
+
+ for error in errors {
+ let before_span = error.obligation.cause.span;
+ if self.adjust_fulfillment_error_for_expr_obligation(error)
+ || before_span != error.obligation.cause.span
+ {
+ // Store both the predicate and the predicate *without constness*
+ // since sometimes we instantiate and check both of these in a
+ // method call, for example.
+ remap_cause.insert((
+ before_span,
+ error.obligation.predicate,
+ error.obligation.cause.clone(),
+ ));
+ remap_cause.insert((
+ before_span,
+ error.obligation.predicate.without_const(self.tcx),
+ error.obligation.cause.clone(),
+ ));
+ } else {
+ // If it failed to be adjusted once around, it may be adjusted
+ // via the "remap cause" mapping the second time...
+ not_adjusted.push(error);
+ }
+ }
+
+ for error in not_adjusted {
+ for (span, predicate, cause) in &remap_cause {
+ if *predicate == error.obligation.predicate
+ && span.contains(error.obligation.cause.span)
+ {
+ error.obligation.cause = cause.clone();
+ continue;
+ }
+ }
+ }
+ }
+
+ fn adjust_fulfillment_error_for_expr_obligation(
+ &self,
+ error: &mut traits::FulfillmentError<'tcx>,
+ ) -> bool {
+ let (traits::ExprItemObligation(def_id, hir_id, idx) | traits::ExprBindingObligation(def_id, _, hir_id, idx))
+ = *error.obligation.cause.code().peel_derives() else { return false; };
+ let hir = self.tcx.hir();
+ let hir::Node::Expr(expr) = hir.get(hir_id) else { return false; };
+
+ // Skip over mentioning async lang item
+ if Some(def_id) == self.tcx.lang_items().from_generator_fn()
+ && error.obligation.cause.span.desugaring_kind()
+ == Some(rustc_span::DesugaringKind::Async)
+ {
+ return false;
+ }
+
+ let Some(unsubstituted_pred) =
+ self.tcx.predicates_of(def_id).instantiate_identity(self.tcx).predicates.into_iter().nth(idx)
+ else { return false; };
+
+ let generics = self.tcx.generics_of(def_id);
+ let predicate_substs = match unsubstituted_pred.kind().skip_binder() {
+ ty::PredicateKind::Trait(pred) => pred.trait_ref.substs,
+ ty::PredicateKind::Projection(pred) => pred.projection_ty.substs,
+ _ => ty::List::empty(),
+ };
+
+ let find_param_matching = |matches: &dyn Fn(&ty::ParamTy) -> bool| {
+ predicate_substs.types().find_map(|ty| {
+ ty.walk().find_map(|arg| {
+ if let ty::GenericArgKind::Type(ty) = arg.unpack()
+ && let ty::Param(param_ty) = ty.kind()
+ && matches(param_ty)
+ {
+ Some(arg)
+ } else {
+ None
+ }
+ })
+ })
+ };
+
+ // Prefer generics that are local to the fn item, since these are likely
+ // to be the cause of the unsatisfied predicate.
+ let mut param_to_point_at = find_param_matching(&|param_ty| {
+ self.tcx.parent(generics.type_param(param_ty, self.tcx).def_id) == def_id
+ });
+ // Fall back to generic that isn't local to the fn item. This will come
+ // from a trait or impl, for example.
+ let mut fallback_param_to_point_at = find_param_matching(&|param_ty| {
+ self.tcx.parent(generics.type_param(param_ty, self.tcx).def_id) != def_id
+ && param_ty.name != rustc_span::symbol::kw::SelfUpper
+ });
+ // Finally, the `Self` parameter is possibly the reason that the predicate
+ // is unsatisfied. This is less likely to be true for methods, because
+ // method probe means that we already kinda check that the predicates due
+ // to the `Self` type are true.
+ let mut self_param_to_point_at =
+ find_param_matching(&|param_ty| param_ty.name == rustc_span::symbol::kw::SelfUpper);
+
+ // Finally, for ambiguity-related errors, we actually want to look
+ // for a parameter that is the source of the inference type left
+ // over in this predicate.
+ if let traits::FulfillmentErrorCode::CodeAmbiguity = error.code {
+ fallback_param_to_point_at = None;
+ self_param_to_point_at = None;
+ param_to_point_at =
+ self.find_ambiguous_parameter_in(def_id, error.root_obligation.predicate);
+ }
+
+ if self.closure_span_overlaps_error(error, expr.span) {
+ return false;
+ }
+
+ match &expr.kind {
+ hir::ExprKind::Path(qpath) => {
+ if let hir::Node::Expr(hir::Expr {
+ kind: hir::ExprKind::Call(callee, args),
+ hir_id: call_hir_id,
+ span: call_span,
+ ..
+ }) = hir.get(hir.get_parent_node(expr.hir_id))
+ && callee.hir_id == expr.hir_id
+ {
+ if self.closure_span_overlaps_error(error, *call_span) {
+ return false;
+ }
+
+ for param in
+ [param_to_point_at, fallback_param_to_point_at, self_param_to_point_at]
+ .into_iter()
+ .flatten()
+ {
+ if self.point_at_arg_if_possible(
+ error,
+ def_id,
+ param,
+ *call_hir_id,
+ callee.span,
+ None,
+ args,
+ )
+ {
+ return true;
+ }
+ }
+ }
+ // Notably, we only point to params that are local to the
+ // item we're checking, since those are the ones we are able
+ // to look in the final `hir::PathSegment` for. Everything else
+ // would require a deeper search into the `qpath` than I think
+ // is worthwhile.
+ if let Some(param_to_point_at) = param_to_point_at
+ && self.point_at_path_if_possible(error, def_id, param_to_point_at, qpath)
+ {
+ return true;
+ }
+ }
+ hir::ExprKind::MethodCall(segment, receiver, args, ..) => {
+ for param in [param_to_point_at, fallback_param_to_point_at, self_param_to_point_at]
+ .into_iter()
+ .flatten()
+ {
+ if self.point_at_arg_if_possible(
+ error,
+ def_id,
+ param,
+ hir_id,
+ segment.ident.span,
+ Some(receiver),
+ args,
+ ) {
+ return true;
+ }
+ }
+ if let Some(param_to_point_at) = param_to_point_at
+ && self.point_at_generic_if_possible(error, def_id, param_to_point_at, segment)
+ {
+ return true;
+ }
+ }
+ hir::ExprKind::Struct(qpath, fields, ..) => {
+ if let Res::Def(DefKind::Struct | DefKind::Variant, variant_def_id) =
+ self.typeck_results.borrow().qpath_res(qpath, hir_id)
+ {
+ for param in
+ [param_to_point_at, fallback_param_to_point_at, self_param_to_point_at]
+ {
+ if let Some(param) = param
+ && self.point_at_field_if_possible(
+ error,
+ def_id,
+ param,
+ variant_def_id,
+ fields,
+ )
+ {
+ return true;
+ }
+ }
+ }
+ if let Some(param_to_point_at) = param_to_point_at
+ && self.point_at_path_if_possible(error, def_id, param_to_point_at, qpath)
+ {
+ return true;
+ }
+ }
+ _ => {}
+ }
+
+ false
+ }
+
+ fn closure_span_overlaps_error(
+ &self,
+ error: &traits::FulfillmentError<'tcx>,
+ span: Span,
+ ) -> bool {
+ if let traits::FulfillmentErrorCode::CodeSelectionError(
+ traits::SelectionError::OutputTypeParameterMismatch(_, expected, _),
+ ) = error.code
+ && let ty::Closure(def_id, _) | ty::Generator(def_id, ..) = expected.skip_binder().self_ty().kind()
+ && span.overlaps(self.tcx.def_span(*def_id))
+ {
+ true
+ } else {
+ false
+ }
+ }
+
+ fn point_at_arg_if_possible(
+ &self,
+ error: &mut traits::FulfillmentError<'tcx>,
+ def_id: DefId,
+ param_to_point_at: ty::GenericArg<'tcx>,
+ call_hir_id: hir::HirId,
+ callee_span: Span,
+ receiver: Option<&'tcx hir::Expr<'tcx>>,
+ args: &'tcx [hir::Expr<'tcx>],
+ ) -> bool {
+ let sig = self.tcx.fn_sig(def_id).skip_binder();
+ let args_referencing_param: Vec<_> = sig
+ .inputs()
+ .iter()
+ .enumerate()
+ .filter(|(_, ty)| find_param_in_ty(**ty, param_to_point_at))
+ .collect();
+ // If there's one field that references the given generic, great!
+ if let [(idx, _)] = args_referencing_param.as_slice()
+ && let Some(arg) = receiver
+ .map_or(args.get(*idx), |rcvr| if *idx == 0 { Some(rcvr) } else { args.get(*idx - 1) }) {
+ error.obligation.cause.span = arg.span.find_ancestor_in_same_ctxt(error.obligation.cause.span).unwrap_or(arg.span);
+ error.obligation.cause.map_code(|parent_code| {
+ ObligationCauseCode::FunctionArgumentObligation {
+ arg_hir_id: arg.hir_id,
+ call_hir_id,
+ parent_code,
+ }
+ });
+ return true;
+ } else if args_referencing_param.len() > 0 {
+ // If more than one argument applies, then point to the callee span at least...
+ // We have chance to fix this up further in `point_at_generics_if_possible`
+ error.obligation.cause.span = callee_span;
+ }
+
+ false
+ }
+
+ fn point_at_field_if_possible(
+ &self,
+ error: &mut traits::FulfillmentError<'tcx>,
+ def_id: DefId,
+ param_to_point_at: ty::GenericArg<'tcx>,
+ variant_def_id: DefId,
+ expr_fields: &[hir::ExprField<'tcx>],
+ ) -> bool {
+ let def = self.tcx.adt_def(def_id);
+
+ let identity_substs = ty::InternalSubsts::identity_for_item(self.tcx, def_id);
+ let fields_referencing_param: Vec<_> = def
+ .variant_with_id(variant_def_id)
+ .fields
+ .iter()
+ .filter(|field| {
+ let field_ty = field.ty(self.tcx, identity_substs);
+ find_param_in_ty(field_ty, param_to_point_at)
+ })
+ .collect();
+
+ if let [field] = fields_referencing_param.as_slice() {
+ for expr_field in expr_fields {
+ // Look for the ExprField that matches the field, using the
+ // same rules that check_expr_struct uses for macro hygiene.
+ if self.tcx.adjust_ident(expr_field.ident, variant_def_id) == field.ident(self.tcx)
+ {
+ error.obligation.cause.span = expr_field
+ .expr
+ .span
+ .find_ancestor_in_same_ctxt(error.obligation.cause.span)
+ .unwrap_or(expr_field.span);
+ return true;
+ }
+ }
+ }
+
+ false
+ }
+
+ fn point_at_path_if_possible(
+ &self,
+ error: &mut traits::FulfillmentError<'tcx>,
+ def_id: DefId,
+ param: ty::GenericArg<'tcx>,
+ qpath: &QPath<'tcx>,
+ ) -> bool {
+ match qpath {
+ hir::QPath::Resolved(_, path) => {
+ if let Some(segment) = path.segments.last()
+ && self.point_at_generic_if_possible(error, def_id, param, segment)
+ {
+ return true;
+ }
+ }
+ hir::QPath::TypeRelative(_, segment) => {
+ if self.point_at_generic_if_possible(error, def_id, param, segment) {
+ return true;
+ }
+ }
+ _ => {}
+ }
+
+ false
+ }
+
+ fn point_at_generic_if_possible(
+ &self,
+ error: &mut traits::FulfillmentError<'tcx>,
+ def_id: DefId,
+ param_to_point_at: ty::GenericArg<'tcx>,
+ segment: &hir::PathSegment<'tcx>,
+ ) -> bool {
+ let own_substs = self
+ .tcx
+ .generics_of(def_id)
+ .own_substs(ty::InternalSubsts::identity_for_item(self.tcx, def_id));
+ let Some((index, _)) = own_substs
+ .iter()
+ .filter(|arg| matches!(arg.unpack(), ty::GenericArgKind::Type(_)))
+ .enumerate()
+ .find(|(_, arg)| **arg == param_to_point_at) else { return false };
+ let Some(arg) = segment
+ .args()
+ .args
+ .iter()
+ .filter(|arg| matches!(arg, hir::GenericArg::Type(_)))
+ .nth(index) else { return false; };
+ error.obligation.cause.span = arg
+ .span()
+ .find_ancestor_in_same_ctxt(error.obligation.cause.span)
+ .unwrap_or(arg.span());
+ true
+ }
+
+ fn find_ambiguous_parameter_in<T: TypeVisitable<'tcx>>(
+ &self,
+ item_def_id: DefId,
+ t: T,
+ ) -> Option<ty::GenericArg<'tcx>> {
+ struct FindAmbiguousParameter<'a, 'tcx>(&'a FnCtxt<'a, 'tcx>, DefId);
+ impl<'tcx> TypeVisitor<'tcx> for FindAmbiguousParameter<'_, 'tcx> {
+ type BreakTy = ty::GenericArg<'tcx>;
+ fn visit_ty(&mut self, ty: Ty<'tcx>) -> std::ops::ControlFlow<Self::BreakTy> {
+ if let Some(origin) = self.0.type_var_origin(ty)
+ && let TypeVariableOriginKind::TypeParameterDefinition(_, Some(def_id)) =
+ origin.kind
+ && let generics = self.0.tcx.generics_of(self.1)
+ && let Some(index) = generics.param_def_id_to_index(self.0.tcx, def_id)
+ && let Some(subst) = ty::InternalSubsts::identity_for_item(self.0.tcx, self.1)
+ .get(index as usize)
+ {
+ ControlFlow::Break(*subst)
+ } else {
+ ty.super_visit_with(self)
+ }
+ }
+ }
+ t.visit_with(&mut FindAmbiguousParameter(self, item_def_id)).break_value()
+ }
+
+ fn label_fn_like(
+ &self,
+ err: &mut Diagnostic,
+ callable_def_id: Option<DefId>,
+ callee_ty: Option<Ty<'tcx>>,
+ // A specific argument should be labeled, instead of all of them
+ expected_idx: Option<usize>,
+ is_method: bool,
+ ) {
+ let Some(mut def_id) = callable_def_id else {
+ return;
+ };
+
+ if let Some(assoc_item) = self.tcx.opt_associated_item(def_id)
+ // Possibly points at either impl or trait item, so try to get it
+ // to point to trait item, then get the parent.
+ // This parent might be an impl in the case of an inherent function,
+ // but the next check will fail.
+ && let maybe_trait_item_def_id = assoc_item.trait_item_def_id.unwrap_or(def_id)
+ && let maybe_trait_def_id = self.tcx.parent(maybe_trait_item_def_id)
+ // Just an easy way to check "trait_def_id == Fn/FnMut/FnOnce"
+ && let Some(call_kind) = ty::ClosureKind::from_def_id(self.tcx, maybe_trait_def_id)
+ && let Some(callee_ty) = callee_ty
+ {
+ let callee_ty = callee_ty.peel_refs();
+ match *callee_ty.kind() {
+ ty::Param(param) => {
+ let param =
+ self.tcx.generics_of(self.body_id.owner).type_param(&param, self.tcx);
+ if param.kind.is_synthetic() {
+ // if it's `impl Fn() -> ..` then just fall down to the def-id based logic
+ def_id = param.def_id;
+ } else {
+ // Otherwise, find the predicate that makes this generic callable,
+ // and point at that.
+ let instantiated = self
+ .tcx
+ .explicit_predicates_of(self.body_id.owner)
+ .instantiate_identity(self.tcx);
+ // FIXME(compiler-errors): This could be problematic if something has two
+ // fn-like predicates with different args, but callable types really never
+ // do that, so it's OK.
+ for (predicate, span) in
+ std::iter::zip(instantiated.predicates, instantiated.spans)
+ {
+ if let ty::PredicateKind::Trait(pred) = predicate.kind().skip_binder()
+ && pred.self_ty().peel_refs() == callee_ty
+ && ty::ClosureKind::from_def_id(self.tcx, pred.def_id()).is_some()
+ {
+ err.span_note(span, "callable defined here");
+ return;
+ }
+ }
+ }
+ }
+ ty::Opaque(new_def_id, _)
+ | ty::Closure(new_def_id, _)
+ | ty::FnDef(new_def_id, _) => {
+ def_id = new_def_id;
+ }
+ _ => {
+ // Look for a user-provided impl of a `Fn` trait, and point to it.
+ let new_def_id = self.probe(|_| {
+ let trait_ref = ty::TraitRef::new(
+ call_kind.to_def_id(self.tcx),
+ self.tcx.mk_substs(
+ [
+ ty::GenericArg::from(callee_ty),
+ self.next_ty_var(TypeVariableOrigin {
+ kind: TypeVariableOriginKind::MiscVariable,
+ span: rustc_span::DUMMY_SP,
+ })
+ .into(),
+ ]
+ .into_iter(),
+ ),
+ );
+ let obligation = traits::Obligation::new(
+ traits::ObligationCause::dummy(),
+ self.param_env,
+ ty::Binder::dummy(ty::TraitPredicate {
+ trait_ref,
+ constness: ty::BoundConstness::NotConst,
+ polarity: ty::ImplPolarity::Positive,
+ }),
+ );
+ match SelectionContext::new(&self).select(&obligation) {
+ Ok(Some(traits::ImplSource::UserDefined(impl_source))) => {
+ Some(impl_source.impl_def_id)
+ }
+ _ => None,
+ }
+ });
+ if let Some(new_def_id) = new_def_id {
+ def_id = new_def_id;
+ } else {
+ return;
+ }
+ }
+ }
+ }
+
+ if let Some(def_span) = self.tcx.def_ident_span(def_id) && !def_span.is_dummy() {
+ let mut spans: MultiSpan = def_span.into();
+
+ let params = self
+ .tcx
+ .hir()
+ .get_if_local(def_id)
+ .and_then(|node| node.body_id())
+ .into_iter()
+ .flat_map(|id| self.tcx.hir().body(id).params)
+ .skip(if is_method { 1 } else { 0 });
+
+ for (_, param) in params
+ .into_iter()
+ .enumerate()
+ .filter(|(idx, _)| expected_idx.map_or(true, |expected_idx| expected_idx == *idx))
+ {
+ spans.push_span_label(param.span, "");
+ }
+
+ let def_kind = self.tcx.def_kind(def_id);
+ err.span_note(spans, &format!("{} defined here", def_kind.descr(def_id)));
+ } else if let Some(hir::Node::Expr(e)) = self.tcx.hir().get_if_local(def_id)
+ && let hir::ExprKind::Closure(hir::Closure { body, .. }) = &e.kind
+ {
+ let param = expected_idx
+ .and_then(|expected_idx| self.tcx.hir().body(*body).params.get(expected_idx));
+ let (kind, span) = if let Some(param) = param {
+ ("closure parameter", param.span)
+ } else {
+ ("closure", self.tcx.def_span(def_id))
+ };
+ err.span_note(span, &format!("{} defined here", kind));
+ } else {
+ let def_kind = self.tcx.def_kind(def_id);
+ err.span_note(
+ self.tcx.def_span(def_id),
+ &format!("{} defined here", def_kind.descr(def_id)),
+ );
+ }
+ }
+}
+
+fn find_param_in_ty<'tcx>(ty: Ty<'tcx>, param_to_point_at: ty::GenericArg<'tcx>) -> bool {
+ let mut walk = ty.walk();
+ while let Some(arg) = walk.next() {
+ if arg == param_to_point_at {
+ return true;
+ } else if let ty::GenericArgKind::Type(ty) = arg.unpack()
+ && let ty::Projection(..) = ty.kind()
+ {
+ // This logic may seem a bit strange, but typically when
+ // we have a projection type in a function signature, the
+ // argument that's being passed into that signature is
+ // not actually constraining that projection's substs in
+ // a meaningful way. So we skip it, and see improvements
+ // in some UI tests.
+ walk.skip_current_subtree();
+ }
+ }
+ false
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-07-25 23:19:55 +0000