fix: Initialize numeric generics' type to a polymorphic integer when …

…used in an expression (#2179)

* Fix 2055

* Add regression test

crates/nargo_cli/tests/execution_success/generics/src/main.nr

@@ -54,4 +54,18 @@ fn main(x: Field, y: Field) {
     let two = y;
     let nested_generics: Bar<Bar<Field>> = Bar { one, two, other: Bar { one, two, other: 0 } };
     assert(nested_generics.other.other == bar1.get_other());
+
+    let _ = regression_2055([1, 2, 3]);
+}
+
+fn regression_2055<LEN>(bytes: [u8; LEN]) -> Field {
+    let mut f = 0;
+    let mut b = 1;
+    let mut len = LEN - 1; // FAILS
+    for i in 0..LEN {
+        let j = len - i;
+        f += (bytes[j] as Field) * b;
+        b *= 256;
+    }
+    f
 }

crates/noirc_frontend/src/hir/resolution/resolver.rs

@@ -1008,7 +1008,16 @@ impl<'a> Resolver<'a> {
                     match self.interner.definition(hir_ident.id).kind {
                         DefinitionKind::Function(_) => {}
                         DefinitionKind::Global(_) => {}
-                        DefinitionKind::GenericType(_) => {}
+                        DefinitionKind::GenericType(_) => {
+                            // Initialize numeric generics to a polymorphic integer type in case
+                            // they're used in expressions. We must do this here since the type
+                            // checker does not check definition kinds and otherwise expects
+                            // parameters to already be typed.
+                            if self.interner.id_type(hir_ident.id) == Type::Error {
+                                let typ = Type::polymorphic_integer(self.interner);
+                                self.interner.push_definition_type(hir_ident.id, typ);
+                            }
+                        }
                         // We ignore the above definition kinds because only local variables can be captured by closures.
                         DefinitionKind::Local(_) => {
                             self.resolve_local_variable(hir_ident, var_scope_index);