From 10f9f14377a2fdf65a1f07497c48ce264816a04a Mon Sep 17 00:00:00 2001 From: Dnreikronos Date: Mon, 1 Jun 2026 13:47:30 -0300 Subject: [PATCH] Build a fully-applied trait ref in method-not-found suggestion When a method call fails to resolve, the suggestion machinery probes all traits for a method with the same name and builds a trait reference for the providing trait to detect duplicate trait items coming from multiple crate versions. It passed only the receiver type as the single argument, which is correct only for traits whose sole generic parameter is `Self`. For a trait with further parameters (for example `Borrow`), or when the receiver type is unknown, the argument list no longer matched the trait's generics and tripped the `debug_assert_args_compatible` assertion, producing an ICE. Build the argument list with `GenericArgs::for_item` instead, using the receiver type for `Self` when known and fresh inference variables for the remaining parameters. --- .../rustc_hir_typeck/src/method/suggest.rs | 19 +++++- ...estion-trait-with-extra-generics-no-ice.rs | 24 +++++++ ...on-trait-with-extra-generics-no-ice.stderr | 65 +++++++++++++++++++ 3 files changed, 107 insertions(+), 1 deletion(-) create mode 100644 tests/ui/methods/method-suggestion-trait-with-extra-generics-no-ice.rs create mode 100644 tests/ui/methods/method-suggestion-trait-with-extra-generics-no-ice.stderr diff --git a/compiler/rustc_hir_typeck/src/method/suggest.rs b/compiler/rustc_hir_typeck/src/method/suggest.rs index c9ec32159f476..48e1f553900b0 100644 --- a/compiler/rustc_hir_typeck/src/method/suggest.rs +++ b/compiler/rustc_hir_typeck/src/method/suggest.rs @@ -4796,7 +4796,24 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { let hir::Node::Expr(rcvr) = self.tcx.hir_node(hir_id) else { return false; }; - let trait_ref = ty::TraitRef::new(self.tcx, trait_def_id, rcvr_ty.into_iter()); + // The trait may have generic parameters beyond `Self` (e.g. `Borrow`), and + // `rcvr_ty` may even be unknown. We only ever know the receiver type (the `Self` arg), + // so fill `Self` from `rcvr_ty` when available and the remaining parameters with fresh + // inference variables; building a `TraitRef` with a partial arg list would otherwise trip + // `debug_assert_args_compatible` and ICE. See #157189. + let trait_ref = ty::TraitRef::new_from_args( + self.tcx, + trait_def_id, + ty::GenericArgs::for_item(self.tcx, trait_def_id, |param, _| { + if param.index == 0 + && let Some(rcvr_ty) = rcvr_ty + { + rcvr_ty.into() + } else { + self.var_for_def(rcvr.span, param) + } + }), + ); let trait_pred = ty::Binder::dummy(ty::TraitPredicate { trait_ref, polarity: ty::PredicatePolarity::Positive, diff --git a/tests/ui/methods/method-suggestion-trait-with-extra-generics-no-ice.rs b/tests/ui/methods/method-suggestion-trait-with-extra-generics-no-ice.rs new file mode 100644 index 0000000000000..0a98cdef5c923 --- /dev/null +++ b/tests/ui/methods/method-suggestion-trait-with-extra-generics-no-ice.rs @@ -0,0 +1,24 @@ +//! Regression test for #157189. +//! +//! When a method call fails to resolve, the "trait which provides `` is +//! implemented but not in scope" diagnostic probes all traits for a method of the +//! same name. Here `.borrow()` matches `std::borrow::Borrow::borrow`, and `Borrow` +//! has a generic parameter (`Borrowed`) besides `Self`. Building the trait +//! reference for the diagnostic used to pass only the receiver type as the single +//! argument, which mismatched the trait's generics and ICEd in +//! `debug_assert_args_compatible`. It should just report the error. + +trait Foo { + extern "C" fn borrow(&self); +} + +struct Bar; + +fn main() { + let foo: Box usize> = Box::new(Bar); + //~^ ERROR expected a `Fn(bool)` closure, found `Bar` + foo.borrow(); + //~^ ERROR no method named `borrow` found + foo.take() + //~^ ERROR `Box usize>` is not an iterator +} diff --git a/tests/ui/methods/method-suggestion-trait-with-extra-generics-no-ice.stderr b/tests/ui/methods/method-suggestion-trait-with-extra-generics-no-ice.stderr new file mode 100644 index 0000000000000..aa46a41fa3378 --- /dev/null +++ b/tests/ui/methods/method-suggestion-trait-with-extra-generics-no-ice.stderr @@ -0,0 +1,65 @@ +error[E0599]: no method named `borrow` found for struct `Box usize>` in the current scope + --> $DIR/method-suggestion-trait-with-extra-generics-no-ice.rs:20:9 + | +LL | foo.borrow(); + | ^^^^^^ + | + --> $SRC_DIR/core/src/borrow.rs:LL:COL + | + = note: the method is available for `Box usize>` here + | + = help: items from traits can only be used if the trait is in scope +help: use parentheses to call this trait object + | +LL | foo(/* bool */).borrow(); + | ++++++++++++ +help: trait `Borrow` which provides `borrow` is implemented but not in scope; perhaps you want to import it + | +LL + use std::borrow::Borrow; + | +help: there is a method `borrow_mut` with a similar name + | +LL | foo.borrow_mut(); + | ++++ + +error[E0277]: expected a `Fn(bool)` closure, found `Bar` + --> $DIR/method-suggestion-trait-with-extra-generics-no-ice.rs:18:43 + | +LL | let foo: Box usize> = Box::new(Bar); + | ^^^^^^^^^^^^^ expected an `Fn(bool)` closure, found `Bar` + | +help: the trait `Fn(bool)` is not implemented for `Bar` + --> $DIR/method-suggestion-trait-with-extra-generics-no-ice.rs:15:1 + | +LL | struct Bar; + | ^^^^^^^^^^ + = note: required for the cast from `Box` to `Box usize>` + +error[E0599]: `Box usize>` is not an iterator + --> $DIR/method-suggestion-trait-with-extra-generics-no-ice.rs:22:9 + | +LL | foo.take() + | ^^^^ + | | + | this is an associated function, not a method + | `Box usize>` is not an iterator + | + = note: found the following associated functions; to be used as methods, functions must have a `self` parameter + = note: the candidate is defined in an impl for the type `Box` + = note: the following trait bounds were not satisfied: + `dyn Fn(bool) -> usize: Iterator` + which is required by `Box usize>: Iterator` + `Box usize>: Iterator` + which is required by `&mut Box usize>: Iterator` + `dyn Fn(bool) -> usize: Iterator` + which is required by `&mut dyn Fn(bool) -> usize: Iterator` +help: use associated function syntax instead + | +LL - foo.take() +LL + Box:: usize>::take(foo) + | + +error: aborting due to 3 previous errors + +Some errors have detailed explanations: E0277, E0599. +For more information about an error, try `rustc --explain E0277`.