chore: add some tests for type aliases

compiler/noirc_frontend/src/tests.rs

@@ -1,5 +1,6 @@
 #![cfg(test)]
 
+mod aliases;
 mod bound_checks;
 mod imports;
 mod metaprogramming;

compiler/noirc_frontend/src/tests/aliases.rs

@@ -0,0 +1,52 @@
+use super::assert_no_errors;
+
+#[test]
+fn allows_usage_of_type_alias_as_argument_type() {
+    let src = r#"
+    type Foo = Field;
+
+    fn accepts_a_foo(x: Foo) {
+        assert_eq(x, 42);
+    }
+
+    fn main() {
+        accepts_a_foo(42);
+    }
+    "#;
+    assert_no_errors(src);
+}
+
+#[test]
+fn allows_usage_of_type_alias_as_return_type() {
+    let src = r#"
+    type Foo = Field;
+
+    fn returns_a_foo() -> Foo {
+        42
+    }
+
+    fn main() {
+        let _ = returns_a_foo();
+    }
+    "#;
+    assert_no_errors(src);
+}
+
+// This is a regression test for https://github.com/noir-lang/noir/issues/6347
+#[test]
+#[should_panic = r#"ResolverError(Expected { span: Span(Span { start: ByteIndex(95), end: ByteIndex(98) }), expected: "type", got: "type alias" }"#]
+fn allows_destructuring_a_type_alias_of_a_struct() {
+    let src = r#"
+    struct Foo {
+        inner: Field
+    }
+
+    type Bar = Foo;
+
+    fn main() {
+        let Bar { inner } = Foo { inner: 42 };
+        assert_eq(inner, 42);
+    }
+    "#;
+    assert_no_errors(src);
+}