feat: turbofish operator in struct constructor (#5607)

# Description

## Problem

Part of #5584

## Summary

This adds support for things like `let foo = Foo::<i32> { x }`.

## Additional Context

None.

## Documentation\*

Check one:
- [x] No documentation needed.
- [ ] Documentation included in this PR.
- [ ] **[For Experimental Features]** Documentation to be submitted in a
separate PR.

# PR Checklist\*

- [x] I have tested the changes locally.
- [x] I have formatted the changes with [Prettier](https://prettier.io/)
and/or `cargo fmt` on default settings.

compiler/noirc_frontend/src/elaborator/expressions.rs

@@ -350,7 +350,7 @@ impl<'context> Elaborator<'context> {
                         &mut object,
                     );
 
-                    self.resolve_turbofish_generics(&func_id, method_call.generics, span)
+                    self.resolve_function_turbofish_generics(&func_id, method_call.generics, span)
                 } else {
                     None
                 };
@@ -408,12 +408,12 @@ impl<'context> Elaborator<'context> {
         &mut self,
         constructor: ConstructorExpression,
     ) -> (HirExpression, Type) {
-        let exclude_last_segment = false;
+        let exclude_last_segment = true;
         self.check_unsupported_turbofish_usage(&constructor.type_name, exclude_last_segment);
 
         let span = constructor.type_name.span();
-        let last_segment = constructor.type_name.last_ident();
-        let is_self_type = last_segment.is_self_type_name();
+        let last_segment = constructor.type_name.last_segment();
+        let is_self_type = last_segment.ident.is_self_type_name();
 
         let (r#type, struct_generics) = if let Some(struct_id) = constructor.struct_type {
             let typ = self.interner.get_struct(struct_id);
@@ -430,6 +430,24 @@ impl<'context> Elaborator<'context> {
             }
         };
 
+        let struct_generics = if let Some(turbofish_generics) = &last_segment.generics {
+            if turbofish_generics.len() == struct_generics.len() {
+                let struct_type = r#type.borrow();
+                self.resolve_turbofish_generics(&struct_type.generics, turbofish_generics.clone())
+            } else {
+                self.push_err(TypeCheckError::GenericCountMismatch {
+                    item: format!("struct {}", last_segment.ident),
+                    expected: struct_generics.len(),
+                    found: turbofish_generics.len(),
+                    span: Span::from(last_segment.ident.span().end()..last_segment.span.end()),
+                });
+
+                struct_generics
+            }
+        } else {
+            struct_generics
+        };
+
         let struct_type = r#type.clone();
         let generics = struct_generics.clone();
 
@@ -444,7 +462,7 @@ impl<'context> Elaborator<'context> {
         });
 
         let struct_id = struct_type.borrow().id;
-        let reference_location = Location::new(last_segment.span(), self.file);
+        let reference_location = Location::new(last_segment.ident.span(), self.file);
         self.interner.add_struct_reference(struct_id, reference_location, is_self_type);
 
         (expr, Type::Struct(struct_type, generics))

compiler/noirc_frontend/src/elaborator/patterns.rs

@@ -15,7 +15,7 @@ use crate::{
     },
     macros_api::{HirExpression, Ident, Path, Pattern},
     node_interner::{DefinitionId, DefinitionKind, ExprId, FuncId, GlobalId, TraitImplKind},
-    Shared, StructType, Type, TypeBindings,
+    ResolvedGeneric, Shared, StructType, Type, TypeBindings,
 };
 
 use super::{Elaborator, ResolverMeta};
@@ -404,28 +404,36 @@ impl<'context> Elaborator<'context> {
     }
 
     /// Resolve generics using the expected kinds of the function we are calling
-    pub(super) fn resolve_turbofish_generics(
+    pub(super) fn resolve_function_turbofish_generics(
         &mut self,
         func_id: &FuncId,
         unresolved_turbofish: Option<Vec<UnresolvedType>>,
         span: Span,
     ) -> Option<Vec<Type>> {
         let direct_generics = self.interner.function_meta(func_id).direct_generics.clone();
 
-        unresolved_turbofish.map(|option_inner| {
-            if option_inner.len() != direct_generics.len() {
+        unresolved_turbofish.map(|unresolved_turbofish| {
+            if unresolved_turbofish.len() != direct_generics.len() {
                 let type_check_err = TypeCheckError::IncorrectTurbofishGenericCount {
                     expected_count: direct_generics.len(),
-                    actual_count: option_inner.len(),
+                    actual_count: unresolved_turbofish.len(),
                     span,
                 };
                 self.push_err(type_check_err);
             }
 
-            let generics_with_types = direct_generics.iter().zip(option_inner);
-            vecmap(generics_with_types, |(generic, unresolved_type)| {
-                self.resolve_type_inner(unresolved_type, &generic.kind)
-            })
+            self.resolve_turbofish_generics(&direct_generics, unresolved_turbofish)
+        })
+    }
+
+    pub(super) fn resolve_turbofish_generics(
+        &mut self,
+        generics: &[ResolvedGeneric],
+        turbofish_generics: Vec<UnresolvedType>,
+    ) -> Vec<Type> {
+        let generics_with_types = generics.iter().zip(turbofish_generics);
+        vecmap(generics_with_types, |(generic, unresolved_type)| {
+            self.resolve_type_inner(unresolved_type, &generic.kind)
         })
     }
 
@@ -446,7 +454,7 @@ impl<'context> Elaborator<'context> {
         // and if the turbofish operator was used.
         let generics = definition_kind.and_then(|definition_kind| match &definition_kind {
             DefinitionKind::Function(function) => {
-                self.resolve_turbofish_generics(function, unresolved_turbofish, span)
+                self.resolve_function_turbofish_generics(function, unresolved_turbofish, span)
             }
             _ => None,
         });

compiler/noirc_frontend/src/tests.rs

@@ -2539,25 +2539,52 @@ fn trait_constraint_on_tuple_type() {
 }
 
 #[test]
-fn turbofish_in_constructor_unsupported_yet() {
+fn turbofish_in_constructor_generics_mismatch() {
     let src = r#"
     struct Foo<T> {
         x: T
     }
 
     fn main() {
-        let _ = Foo::<i32> { x: 1 };
+        let _ = Foo::<i32, i64> { x: 1 };
     }
     "#;
+
     let errors = get_program_errors(src);
     assert_eq!(errors.len(), 1);
-
     assert!(matches!(
         errors[0].0,
-        CompilationError::TypeError(TypeCheckError::UnsupportedTurbofishUsage { .. }),
+        CompilationError::TypeError(TypeCheckError::GenericCountMismatch { .. }),
     ));
 }
 
+#[test]
+fn turbofish_in_constructor() {
+    let src = r#"
+    struct Foo<T> {
+        x: T
+    }
+
+    fn main() {
+        let x: Field = 0;
+        let _ = Foo::<i32> { x: x };
+    }
+    "#;
+
+    let errors = get_program_errors(src);
+    assert_eq!(errors.len(), 1);
+
+    let CompilationError::TypeError(TypeCheckError::TypeMismatch {
+        expected_typ, expr_typ, ..
+    }) = &errors[0].0
+    else {
+        panic!("Expected a type mismatch error, got {:?}", errors[0].0);
+    };
+
+    assert_eq!(expected_typ, "i32");
+    assert_eq!(expr_typ, "Field");
+}
+
 #[test]
 fn turbofish_in_middle_of_variable_unsupported_yet() {
     let src = r#"

test_programs/execution_success/slice_regex/Nargo.toml

@@ -1,5 +1,5 @@
 [package]
-name = "regex"
+name = "slice_regex"
 type = "bin"
 authors = [""]
 compiler_version = ">=0.31.0"