fix: bind self when type-checking AsTraitPath

.github/critical_libraries_status/noir-lang/noir_bigcurve/.failures.jsonl

@@ -1 +0,0 @@
-{"suite":"noir_bigcurve","name":"utils::derive_offset_generators::test_compute_and_print_offset_generators"}

compiler/noirc_frontend/src/elaborator/expressions.rs

@@ -4,7 +4,7 @@ use noirc_errors::{Located, Location};
 use rustc_hash::FxHashSet as HashSet;
 
 use crate::{
-    DataType, Kind, QuotedType, Shared, Type, TypeVariable,
+    DataType, Kind, QuotedType, Shared, Type, TypeBindings, TypeVariable,
     ast::{
         ArrayLiteral, AsTraitPath, BinaryOpKind, BlockExpression, CallExpression, CastExpression,
         ConstrainExpression, ConstrainKind, ConstructorExpression, Expression, ExpressionKind,
@@ -1474,6 +1474,9 @@ impl Elaborator<'_> {
         let constraint = TraitConstraint { typ, trait_bound };
 
         let the_trait = self.interner.get_trait(constraint.trait_bound.trait_id);
+        let self_type = the_trait.self_type_typevar.clone();
+        let kind = the_trait.self_type_typevar.kind();
+
         let Some(definition) =
             the_trait.find_method_or_constant(path.impl_item.as_str(), self.interner)
         else {
@@ -1496,7 +1499,21 @@ impl Elaborator<'_> {
         let id = self.interner.push_expr(HirExpression::Ident(ident.clone(), None));
         self.interner.push_expr_location(id, location);
 
-        let typ = self.type_check_variable(ident, id, None);
+        let mut bindings = TypeBindings::default();
+
+        // In `<Type as Trait>::method` we know `Self` is `Type` so we bind that now
+        bindings.insert(self_type.id(), (self_type, kind, constraint.typ.clone()));
+
+        // TODO: set this to `true`. See https://github.com/noir-lang/noir/issues/8687
+        let push_required_type_variables = self.current_trait.is_none();
+
+        let typ = self.type_check_variable_with_bindings(
+            ident,
+            id,
+            None,
+            bindings,
+            push_required_type_variables,
+        );
         self.interner.push_expr_type(id, typ.clone());
         (id, typ)
     }

compiler/noirc_frontend/src/tests/traits.rs

@@ -1783,3 +1783,24 @@ fn ambiguous_associated_type() {
     "#;
     check_errors!(src);
 }
+
+#[named]
+#[test]
+fn as_trait_path_self_type() {
+    let src = r#"
+    pub trait BigCurve<B> {
+        fn one() -> Self;
+    }
+
+    struct Bn254 {}
+
+    impl<B> BigCurve<B> for Bn254 {
+        fn one() -> Self { Bn254 {} }
+    }
+
+    fn main() {
+        let _ = <Bn254 as BigCurve<()>>::one();
+    }
+    "#;
+    assert_no_errors!(src);
+}

test_programs/compile_success_no_bug/noirc_frontend_tests_traits_as_trait_path_self_type/Nargo.toml

@@ -0,0 +1,7 @@
+
+            [package]
+            name = "noirc_frontend_tests_traits_as_trait_path_self_type"
+            type = "bin"
+            authors = [""]
+
+            [dependencies]

test_programs/compile_success_no_bug/noirc_frontend_tests_traits_as_trait_path_self_type/src/main.nr

@@ -0,0 +1,15 @@
+
+    pub trait BigCurve<B> {
+        fn one() -> Self;
+    }
+
+    struct Bn254 {}
+
+    impl<B> BigCurve<B> for Bn254 {
+        fn one() -> Self { Bn254 {} }
+    }
+
+    fn main() {
+        let _ = <Bn254 as BigCurve<()>>::one();
+    }
+

test_programs/compile_success_no_bug/noirc_frontend_tests_traits_as_trait_path_self_type/src_hash.txt

@@ -0,0 +1 @@
+14346112081613033525