fix: allow calling trait impl method from struct if multiple impls ex…

…ist (#7124)

compiler/noirc_frontend/src/ast/statement.rs

@@ -12,6 +12,7 @@ use super::{
 };
 use crate::ast::UnresolvedTypeData;
 use crate::elaborator::types::SELF_TYPE_NAME;
+use crate::elaborator::Turbofish;
 use crate::lexer::token::SpannedToken;
 use crate::node_interner::{
     InternedExpressionKind, InternedPattern, InternedStatementKind, NodeInterner,
@@ -535,6 +536,12 @@ impl PathSegment {
     pub fn turbofish_span(&self) -> Span {
         Span::from(self.ident.span().end()..self.span.end())
     }
+
+    pub fn turbofish(&self) -> Option<Turbofish> {
+        self.generics
+            .as_ref()
+            .map(|generics| Turbofish { span: self.turbofish_span(), generics: generics.clone() })
+    }
 }
 
 impl From<Ident> for PathSegment {

compiler/noirc_frontend/src/elaborator/mod.rs

@@ -61,6 +61,7 @@ mod unquote;
 use fm::FileId;
 use iter_extended::vecmap;
 use noirc_errors::{Location, Span, Spanned};
+pub use path_resolution::Turbofish;
 use path_resolution::{PathResolution, PathResolutionItem};
 use types::bind_ordered_generics;
 

compiler/noirc_frontend/src/elaborator/path_resolution.rs

@@ -227,13 +227,7 @@ impl<'context> Elaborator<'context> {
                 ModuleDefId::TypeId(id) => (
                     id.module_id(),
                     true,
-                    IntermediatePathResolutionItem::Struct(
-                        id,
-                        last_segment_generics.as_ref().map(|generics| Turbofish {
-                            generics: generics.clone(),
-                            span: last_segment.turbofish_span(),
-                        }),
-                    ),
+                    IntermediatePathResolutionItem::Struct(id, last_segment.turbofish()),
                 ),
                 ModuleDefId::TypeAliasId(id) => {
                     let type_alias = self.interner.get_type_alias(id);
@@ -244,25 +238,13 @@ impl<'context> Elaborator<'context> {
                     (
                         module_id,
                         true,
-                        IntermediatePathResolutionItem::TypeAlias(
-                            id,
-                            last_segment_generics.as_ref().map(|generics| Turbofish {
-                                generics: generics.clone(),
-                                span: last_segment.turbofish_span(),
-                            }),
-                        ),
+                        IntermediatePathResolutionItem::TypeAlias(id, last_segment.turbofish()),
                     )
                 }
                 ModuleDefId::TraitId(id) => (
                     id.0,
                     false,
-                    IntermediatePathResolutionItem::Trait(
-                        id,
-                        last_segment_generics.as_ref().map(|generics| Turbofish {
-                            generics: generics.clone(),
-                            span: last_segment.turbofish_span(),
-                        }),
-                    ),
+                    IntermediatePathResolutionItem::Trait(id, last_segment.turbofish()),
                 ),
                 ModuleDefId::FunctionId(_) => panic!("functions cannot be in the type namespace"),
                 ModuleDefId::GlobalId(_) => panic!("globals cannot be in the type namespace"),

compiler/noirc_frontend/src/elaborator/types.rs

@@ -684,6 +684,60 @@ impl<'context> Elaborator<'context> {
         None
     }
 
+    /// This resolves a method in the form `Struct::method` where `method` is a trait method
+    fn resolve_struct_trait_method(&mut self, path: &Path) -> Option<TraitPathResolution> {
+        if path.segments.len() < 2 {
+            return None;
+        }
+
+        let mut path = path.clone();
+        let span = path.span();
+        let last_segment = path.pop();
+        let before_last_segment = path.last_segment();
+
+        let path_resolution = self.resolve_path(path).ok()?;
+        let PathResolutionItem::Struct(struct_id) = path_resolution.item else {
+            return None;
+        };
+
+        let struct_type = self.get_struct(struct_id);
+        let generics = struct_type.borrow().instantiate(self.interner);
+        let typ = Type::Struct(struct_type, generics);
+        let method_name = &last_segment.ident.0.contents;
+
+        // If we can find a method on the struct, this is definitely not a trait method
+        if self.interner.lookup_direct_method(&typ, method_name, false).is_some() {
+            return None;
+        }
+
+        let trait_methods = self.interner.lookup_trait_methods(&typ, method_name, false);
+        if trait_methods.is_empty() {
+            return None;
+        }
+
+        let (hir_method_reference, error) =
+            self.get_trait_method_in_scope(&trait_methods, method_name, last_segment.span);
+        let hir_method_reference = hir_method_reference?;
+        let func_id = hir_method_reference.func_id(self.interner)?;
+        let HirMethodReference::TraitMethodId(trait_method_id, _, _) = hir_method_reference else {
+            return None;
+        };
+
+        let trait_id = trait_method_id.trait_id;
+        let trait_ = self.interner.get_trait(trait_id);
+        let mut constraint = trait_.as_constraint(span);
+        constraint.typ = typ;
+
+        let method = TraitMethod { method_id: trait_method_id, constraint, assumed: false };
+        let turbofish = before_last_segment.turbofish();
+        let item = PathResolutionItem::TraitFunction(trait_id, turbofish, func_id);
+        let mut errors = path_resolution.errors;
+        if let Some(error) = error {
+            errors.push(error);
+        }
+        Some(TraitPathResolution { method, item: Some(item), errors })
+    }
+
     // Try to resolve the given trait method path.
     //
     // Returns the trait method, trait constraint, and whether the impl is assumed to exist by a where clause or not
@@ -695,6 +749,7 @@ impl<'context> Elaborator<'context> {
         self.resolve_trait_static_method_by_self(path)
             .or_else(|| self.resolve_trait_static_method(path))
             .or_else(|| self.resolve_trait_method_by_named_generic(path))
+            .or_else(|| self.resolve_struct_trait_method(path))
     }
 
     pub(super) fn unify(
@@ -1456,6 +1511,19 @@ impl<'context> Elaborator<'context> {
         method_name: &str,
         span: Span,
     ) -> Option<HirMethodReference> {
+        let (method, error) = self.get_trait_method_in_scope(trait_methods, method_name, span);
+        if let Some(error) = error {
+            self.push_err(error);
+        }
+        method
+    }
+
+    fn get_trait_method_in_scope(
+        &mut self,
+        trait_methods: &[(FuncId, TraitId)],
+        method_name: &str,
+        span: Span,
+    ) -> (Option<HirMethodReference>, Option<PathResolutionError>) {
         let module_id = self.module_id();
         let module_data = self.get_module(module_id);
 
@@ -1489,28 +1557,24 @@ impl<'context> Elaborator<'context> {
                 let trait_id = *traits.iter().next().unwrap();
                 let trait_ = self.interner.get_trait(trait_id);
                 let trait_name = self.fully_qualified_trait_path(trait_);
-
-                self.push_err(PathResolutionError::TraitMethodNotInScope {
+                let method =
+                    self.trait_hir_method_reference(trait_id, trait_methods, method_name, span);
+                let error = PathResolutionError::TraitMethodNotInScope {
                     ident: Ident::new(method_name.into(), span),
                     trait_name,
-                });
-
-                return Some(self.trait_hir_method_reference(
-                    trait_id,
-                    trait_methods,
-                    method_name,
-                    span,
-                ));
+                };
+                return (Some(method), Some(error));
             } else {
                 let traits = vecmap(traits, |trait_id| {
                     let trait_ = self.interner.get_trait(trait_id);
                     self.fully_qualified_trait_path(trait_)
                 });
-                self.push_err(PathResolutionError::UnresolvedWithPossibleTraitsToImport {
+                let method = None;
+                let error = PathResolutionError::UnresolvedWithPossibleTraitsToImport {
                     ident: Ident::new(method_name.into(), span),
                     traits,
-                });
-                return None;
+                };
+                return (method, Some(error));
             }
         }
 
@@ -1519,15 +1583,18 @@ impl<'context> Elaborator<'context> {
                 let trait_ = self.interner.get_trait(trait_id);
                 self.fully_qualified_trait_path(trait_)
             });
-            self.push_err(PathResolutionError::MultipleTraitsInScope {
+            let method = None;
+            let error = PathResolutionError::MultipleTraitsInScope {
                 ident: Ident::new(method_name.into(), span),
                 traits,
-            });
-            return None;
+            };
+            return (method, Some(error));
         }
 
         let trait_id = traits_in_scope[0].0;
-        Some(self.trait_hir_method_reference(trait_id, trait_methods, method_name, span))
+        let method = self.trait_hir_method_reference(trait_id, trait_methods, method_name, span);
+        let error = None;
+        (Some(method), error)
     }
 
     fn trait_hir_method_reference(
@@ -1545,7 +1612,7 @@ impl<'context> Elaborator<'context> {
 
         // Return a TraitMethodId with unbound generics. These will later be bound by the type-checker.
         let trait_ = self.interner.get_trait(trait_id);
-        let generics = trait_.as_constraint(span).trait_bound.trait_generics;
+        let generics = trait_.get_trait_generics(span);
         let trait_method_id = trait_.find_method(method_name).unwrap();
         HirMethodReference::TraitMethodId(trait_method_id, generics, false)
     }

compiler/noirc_frontend/src/hir_def/traits.rs

@@ -186,22 +186,22 @@ impl Trait {
         (ordered, named)
     }
 
-    /// Returns a TraitConstraint for this trait using Self as the object
-    /// type and the uninstantiated generics for any trait generics.
-    pub fn as_constraint(&self, span: Span) -> TraitConstraint {
+    pub fn get_trait_generics(&self, span: Span) -> TraitGenerics {
         let ordered = vecmap(&self.generics, |generic| generic.clone().as_named_generic());
         let named = vecmap(&self.associated_types, |generic| {
             let name = Ident::new(generic.name.to_string(), span);
             NamedType { name, typ: generic.clone().as_named_generic() }
         });
+        TraitGenerics { ordered, named }
+    }
 
+    /// Returns a TraitConstraint for this trait using Self as the object
+    /// type and the uninstantiated generics for any trait generics.
+    pub fn as_constraint(&self, span: Span) -> TraitConstraint {
+        let trait_generics = self.get_trait_generics(span);
         TraitConstraint {
             typ: Type::TypeVariable(self.self_type_typevar.clone()),
-            trait_bound: ResolvedTraitBound {
-                trait_generics: TraitGenerics { ordered, named },
-                trait_id: self.id,
-                span,
-            },
+            trait_bound: ResolvedTraitBound { trait_generics, trait_id: self.id, span },
         }
     }
 }

compiler/noirc_frontend/src/tests/traits.rs

@@ -1341,9 +1341,7 @@ fn regression_6530() {
     assert_eq!(errors.len(), 0);
 }
 
-// See https://github.com/noir-lang/noir/issues/7090
 #[test]
-#[should_panic]
 fn calls_trait_method_using_struct_name_when_multiple_impls_exist() {
     let src = r#"
     trait From2<T> {
@@ -1367,3 +1365,32 @@ fn calls_trait_method_using_struct_name_when_multiple_impls_exist() {
     "#;
     assert_no_errors(src);
 }
+
+#[test]
+fn calls_trait_method_using_struct_name_when_multiple_impls_exist_and_errors_turbofish() {
+    let src = r#"
+    trait From2<T> {
+        fn from2(input: T) -> Self;
+    }
+    struct U60Repr {}
+    impl From2<[Field; 3]> for U60Repr {
+        fn from2(_: [Field; 3]) -> Self {
+            U60Repr {}
+        }
+    }
+    impl From2<Field> for U60Repr {
+        fn from2(_: Field) -> Self {
+            U60Repr {}
+        }
+    }
+    fn main() {
+        let _ = U60Repr::<Field>::from2([1, 2, 3]);
+    }
+    "#;
+    let errors = get_program_errors(src);
+    assert_eq!(errors.len(), 1);
+    assert!(matches!(
+        errors[0].0,
+        CompilationError::TypeError(TypeCheckError::TypeMismatch { .. })
+    ));
+}