diff --git a/compiler/noirc_frontend/src/elaborator/expressions.rs b/compiler/noirc_frontend/src/elaborator/expressions.rs index 295297cc738..6e2756f0301 100644 --- a/compiler/noirc_frontend/src/elaborator/expressions.rs +++ b/compiler/noirc_frontend/src/elaborator/expressions.rs @@ -553,7 +553,7 @@ impl<'context> Elaborator<'context> { fn elaborate_cast(&mut self, cast: CastExpression, span: Span) -> (HirExpression, Type) { let (lhs, lhs_type) = self.elaborate_expression(cast.lhs); let r#type = self.resolve_type(cast.r#type); - let result = self.check_cast(lhs_type, &r#type, span); + let result = self.check_cast(&lhs_type, &r#type, span); let expr = HirExpression::Cast(HirCastExpression { lhs, r#type }); (expr, result) } diff --git a/compiler/noirc_frontend/src/elaborator/types.rs b/compiler/noirc_frontend/src/elaborator/types.rs index c134820811e..0973e592c1e 100644 --- a/compiler/noirc_frontend/src/elaborator/types.rs +++ b/compiler/noirc_frontend/src/elaborator/types.rs @@ -779,7 +779,7 @@ impl<'context> Elaborator<'context> { } } - pub(super) fn check_cast(&mut self, from: Type, to: &Type, span: Span) -> Type { + pub(super) fn check_cast(&mut self, from: &Type, to: &Type, span: Span) -> Type { match from.follow_bindings() { Type::Integer(..) | Type::FieldElement @@ -788,8 +788,13 @@ impl<'context> Elaborator<'context> { | Type::Bool => (), Type::TypeVariable(_, _) => { - self.push_err(TypeCheckError::TypeAnnotationsNeeded { span }); - return Type::Error; + // NOTE: in reality the expected type can also include bool, but for the compiler's simplicity + // we only allow integer types. If a bool is in `from` it will need an explicit type annotation. + let expected = Type::polymorphic_integer_or_field(self.interner); + self.unify(from, &expected, || TypeCheckError::InvalidCast { + from: from.clone(), + span, + }); } Type::Error => return Type::Error, from => { diff --git a/compiler/noirc_frontend/src/tests.rs b/compiler/noirc_frontend/src/tests.rs index 91644ff4470..8ce430b6e48 100644 --- a/compiler/noirc_frontend/src/tests.rs +++ b/compiler/noirc_frontend/src/tests.rs @@ -2809,3 +2809,40 @@ fn uses_self_type_in_trait_where_clause() { assert_eq!(method_name, "trait_func"); } + +#[test] +fn do_not_eagerly_error_on_cast_on_type_variable() { + let src = r#" + pub fn foo(x: T, f: fn(T) -> U) -> U { + f(x) + } + + fn main() { + let x: u8 = 1; + let _: Field = foo(x, |x| x as Field); + } + "#; + assert_no_errors(src); +} + +#[test] +fn error_on_cast_over_type_variable() { + let src = r#" + pub fn foo(x: T, f: fn(T) -> U) -> U { + f(x) + } + + fn main() { + let x = "a"; + let _: Field = foo(x, |x| x as Field); + } + "#; + + let errors = get_program_errors(src); + assert_eq!(errors.len(), 1); + + assert!(matches!( + errors[0].0, + CompilationError::TypeError(TypeCheckError::TypeMismatch { .. }) + )); +}