fix(hygiene): Resolve lifetime params from impl blocks in generic args

Early-bound lifetime parameters no longer store the def id of the parameter definition directly. Instead, the parameter index has to be applied to the correct binding item manually. This is almost always the closest owner node, which we now use instead.

Author: zalanlevai

mutest-emit/src/codegen/hygiene.rs

@@ -718,7 +718,7 @@ impl<'tcx, 'op> MacroExpansionSanitizer<'tcx, 'op> {
                         let parent_def_id = self.tcx.parent(qres.def_id());
                         match self.tcx.def_kind(parent_def_id) {
                             hir::DefKind::Trait | hir::DefKind::TraitAlias => {
-                                let qself_ty_ast = self.sanitize_ty(qself_ty, parent_def_id, qself_ty_hir.span);
+                                let qself_ty_ast = self.sanitize_ty(qself_ty, node_hir_id.owner.to_def_id(), qself_ty_hir.span);
 
                                 let parent_path_segment_res = match &path.segments[..] {
                                     [.., parent_path_segment, _] => self.def_res.node_res(parent_path_segment.id),
@@ -737,7 +737,7 @@ impl<'tcx, 'op> MacroExpansionSanitizer<'tcx, 'op> {
                                             let trait_generics = self.tcx.generics_of(parent_def_id);
                                             let trait_args = &node_args[(trait_generics.has_self as usize)..trait_generics.count()];
 
-                                            self.sanitize_generic_args(trait_args, parent_def_id, qself_ty_hir.span)
+                                            self.sanitize_generic_args(trait_args, node_hir_id.owner.to_def_id(), qself_ty_hir.span)
                                         }
 
                                         // Bound params from local trait bounds corresponding to parameter types to the trait subpath.
@@ -864,7 +864,7 @@ impl<'tcx, 'op> MacroExpansionSanitizer<'tcx, 'op> {
                             }
 
                             hir::DefKind::Impl { of_trait: false } => {
-                                let qself_ty_ast = self.sanitize_ty(qself_ty, parent_def_id, qself_ty_hir.span);
+                                let qself_ty_ast = self.sanitize_ty(qself_ty, node_hir_id.owner.to_def_id(), qself_ty_hir.span);
 
                                 // NOTE: We always add a qualified self type, so we can safely ignore the indicator return value.
                                 let _ = self.sanitize_path(path, qres.expect_non_local(), None);

tests/ui/hygiene/resolve_lifetime_generic_param_arg.rs

@@ -0,0 +1,23 @@
+//@ build
+//@ stderr: empty
+
+#![feature(decl_macro)]
+
+#![allow(unused)]
+
+macro m() {
+    trait TraitWithLifetimeParam<'a> {
+        type Value;
+        fn f() -> Self::Value;
+    }
+
+    // TEST: Early-bound lifetime parameter from impl block.
+    struct StructWithLifetimeParam<'a>(std::marker::PhantomData<&'a ()>);
+    impl<'a> TraitWithLifetimeParam<'a> for StructWithLifetimeParam<'a> {
+        type Value = ();
+        // NOTE: `Self` triggers the hygienic expansion into `StructWithLifetimeParam<'a>`.
+        fn f() -> Self::Value {}
+    }
+}
+
+m!();