diff options
Diffstat (limited to 'compiler/rustc_typeck/src/check/fn_ctxt/checks.rs')
| -rw-r--r-- | compiler/rustc_typeck/src/check/fn_ctxt/checks.rs | 1900 |
1 files changed, 1900 insertions, 0 deletions
diff --git a/compiler/rustc_typeck/src/check/fn_ctxt/checks.rs b/compiler/rustc_typeck/src/check/fn_ctxt/checks.rs new file mode 100644 index 000000000..660e7e4e3 --- /dev/null +++ b/compiler/rustc_typeck/src/check/fn_ctxt/checks.rs @@ -0,0 +1,1900 @@ +use crate::astconv::AstConv; +use crate::check::coercion::CoerceMany; +use crate::check::fn_ctxt::arg_matrix::{ + ArgMatrix, Compatibility, Error, ExpectedIdx, ProvidedIdx, +}; +use crate::check::gather_locals::Declaration; +use crate::check::intrinsicck::InlineAsmCtxt; +use crate::check::method::MethodCallee; +use crate::check::Expectation::*; +use crate::check::TupleArgumentsFlag::*; +use crate::check::{ + potentially_plural_count, struct_span_err, BreakableCtxt, Diverges, Expectation, FnCtxt, + LocalTy, Needs, TupleArgumentsFlag, +}; +use crate::structured_errors::StructuredDiagnostic; + +use rustc_ast as ast; +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_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}; +use rustc_session::Session; +use rustc_span::symbol::Ident; +use rustc_span::{self, Span}; +use rustc_trait_selection::traits::{self, ObligationCauseCode, SelectionContext}; + +use std::iter; +use std::slice; + +impl<'a, 'tcx> FnCtxt<'a, 'tcx> { + pub(in super::super) fn check_casts(&self) { + let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut(); + debug!("FnCtxt::check_casts: {} deferred checks", deferred_cast_checks.len()); + for cast in deferred_cast_checks.drain(..) { + cast.check(self); + } + } + + 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, span) in deferred_transmute_checks.drain(..) { + self.check_transmute(span, from, to); + } + } + + 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); + InlineAsmCtxt::new_in_fn(self) + .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 aguments + // 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(); + + // 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_and_mutate_fulfillment(coerced_ty, |errors| { + self.point_at_type_arg_instead_of_call_if_possible(errors, call_expr); + self.point_at_arg_instead_of_call_if_possible( + errors, + call_expr, + call_span, + provided_args, + &expected_input_tys, + ); + }); + + 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); + } + + // 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, |errors| { + self.point_at_type_arg_instead_of_call_if_possible(errors, call_expr); + self.point_at_arg_instead_of_call_if_possible( + errors, + call_expr, + call_span, + &provided_args, + &expected_input_tys, + ); + }) + } + + // 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 crate::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) = 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)) + } else { + (call_span, *span, None) + } + } + hir::ExprKind::Call(hir::Expr { span, .. }, _) => (call_span, *span, None), + 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 + }; + ( + *span, ident_span, None, // methods are never ctors + ) + } + 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(_, callee, _) => { + 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(&callee[0]) + } 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(None); + } + + // 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.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); + 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(error)) = 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 let Some(e) = error { + if !matches!(trace.cause.as_failure_code(e), FailureCode::Error0308(_)) { + self.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.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); + 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.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); + + // 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 = 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())) + ); + 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( + error_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::SelfTy { .. } => 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(path_span, did, substs); + + 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.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)); + 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)); + 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 vec of evaluated `FulfillmentError`s and an `fn` call argument expressions, we walk + /// the checked and coerced types for each argument to see if any of the `FulfillmentError`s + /// reference a type argument. The reason to walk also the checked type is that the coerced type + /// can be not easily comparable with predicate type (because of coercion). If the types match + /// for either checked or coerced type, and there's only *one* argument that does, we point at + /// the corresponding argument's expression span instead of the `fn` call path span. + fn point_at_arg_instead_of_call_if_possible( + &self, + errors: &mut Vec<traits::FulfillmentError<'tcx>>, + expr: &'tcx hir::Expr<'tcx>, + call_sp: Span, + args: &'tcx [hir::Expr<'tcx>], + expected_tys: &[Ty<'tcx>], + ) { + // We *do not* do this for desugared call spans to keep good diagnostics when involving + // the `?` operator. + if call_sp.desugaring_kind().is_some() { + return; + } + + 'outer: for error in errors { + // Only if the cause is somewhere inside the expression we want try to point at arg. + // Otherwise, it means that the cause is somewhere else and we should not change + // anything because we can break the correct span. + if !call_sp.contains(error.obligation.cause.span) { + continue; + } + + // Peel derived obligation, because it's the type that originally + // started this inference chain that matters, not the one we wound + // up with at the end. + fn unpeel_to_top<'a, 'tcx>( + mut code: &'a ObligationCauseCode<'tcx>, + ) -> &'a ObligationCauseCode<'tcx> { + let mut result_code = code; + loop { + let parent = match code { + ObligationCauseCode::ImplDerivedObligation(c) => &c.derived.parent_code, + ObligationCauseCode::BuiltinDerivedObligation(c) + | ObligationCauseCode::DerivedObligation(c) => &c.parent_code, + _ => break result_code, + }; + (result_code, code) = (code, parent); + } + } + let self_: ty::subst::GenericArg<'_> = + match unpeel_to_top(error.obligation.cause.code()) { + ObligationCauseCode::BuiltinDerivedObligation(code) + | ObligationCauseCode::DerivedObligation(code) => { + code.parent_trait_pred.self_ty().skip_binder().into() + } + ObligationCauseCode::ImplDerivedObligation(code) => { + code.derived.parent_trait_pred.self_ty().skip_binder().into() + } + _ if let ty::PredicateKind::Trait(predicate) = + error.obligation.predicate.kind().skip_binder() => + { + predicate.self_ty().into() + } + _ => continue, + }; + let self_ = self.resolve_vars_if_possible(self_); + let ty_matches_self = |ty: Ty<'tcx>| ty.walk().any(|arg| arg == self_); + + let typeck_results = self.typeck_results.borrow(); + + for (idx, arg) in args.iter().enumerate() { + // Don't adjust the span if we already have a more precise span + // within one of the args. + if arg.span.contains(error.obligation.cause.span) { + let references_arg = + typeck_results.expr_ty_opt(arg).map_or(false, &ty_matches_self) + || expected_tys.get(idx).copied().map_or(false, &ty_matches_self); + if references_arg && !arg.span.from_expansion() { + error.obligation.cause.map_code(|parent_code| { + ObligationCauseCode::FunctionArgumentObligation { + arg_hir_id: args[idx].hir_id, + call_hir_id: expr.hir_id, + parent_code, + } + }) + } + continue 'outer; + } + } + + // Collect the argument position for all arguments that could have caused this + // `FulfillmentError`. + let mut referenced_in: Vec<_> = std::iter::zip(expected_tys, args) + .enumerate() + .flat_map(|(idx, (expected_ty, arg))| { + if let Some(arg_ty) = typeck_results.expr_ty_opt(arg) { + vec![(idx, arg_ty), (idx, *expected_ty)] + } else { + vec![] + } + }) + .filter_map(|(i, ty)| { + let ty = self.resolve_vars_if_possible(ty); + // We walk the argument type because the argument's type could have + // been `Option<T>`, but the `FulfillmentError` references `T`. + if ty_matches_self(ty) { Some(i) } else { None } + }) + .collect(); + + // Both checked and coerced types could have matched, thus we need to remove + // duplicates. + + // We sort primitive type usize here and can use unstable sort + referenced_in.sort_unstable(); + referenced_in.dedup(); + + if let &[idx] = &referenced_in[..] { + // Do not point at the inside of a macro. + // That would often result in poor error messages. + if args[idx].span.from_expansion() { + continue; + } + // We make sure that only *one* argument matches the obligation failure + // and we assign the obligation's span to its expression's. + error.obligation.cause.span = args[idx].span; + error.obligation.cause.map_code(|parent_code| { + ObligationCauseCode::FunctionArgumentObligation { + arg_hir_id: args[idx].hir_id, + call_hir_id: expr.hir_id, + parent_code, + } + }); + } else if error.obligation.cause.span == call_sp { + // Make function calls point at the callee, not the whole thing. + if let hir::ExprKind::Call(callee, _) = expr.kind { + error.obligation.cause.span = callee.span; + } + } + } + } + + /// Given a vec of evaluated `FulfillmentError`s and an `fn` call expression, we walk the + /// `PathSegment`s and resolve their type parameters to see if any of the `FulfillmentError`s + /// were caused by them. If they were, we point at the corresponding type argument's span + /// instead of the `fn` call path span. + fn point_at_type_arg_instead_of_call_if_possible( + &self, + errors: &mut Vec<traits::FulfillmentError<'tcx>>, + call_expr: &'tcx hir::Expr<'tcx>, + ) { + if let hir::ExprKind::Call(path, _) = &call_expr.kind { + if let hir::ExprKind::Path(hir::QPath::Resolved(_, path)) = &path.kind { + for error in errors { + if let ty::PredicateKind::Trait(predicate) = + error.obligation.predicate.kind().skip_binder() + { + // If any of the type arguments in this path segment caused the + // `FulfillmentError`, point at its span (#61860). + for arg in path + .segments + .iter() + .filter_map(|seg| seg.args.as_ref()) + .flat_map(|a| a.args.iter()) + { + if let hir::GenericArg::Type(hir_ty) = &arg + && let Some(ty) = + self.typeck_results.borrow().node_type_opt(hir_ty.hir_id) + && self.resolve_vars_if_possible(ty) == predicate.self_ty() + { + error.obligation.cause.span = hir_ty.span; + break; + } + } + } + } + } + } + } + + fn label_fn_like( + &self, + err: &mut rustc_errors::DiagnosticBuilder<'tcx, rustc_errors::ErrorGuaranteed>, + callable_def_id: Option<DefId>, + callee_ty: Option<Ty<'tcx>>, + ) { + 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(¶m, 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); + + for param in params { + 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 { + 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)), + ); + } + } +} |