From a53f5ed86ad9a372ecad8a0367f7af3a843aae56 Mon Sep 17 00:00:00 2001
From: jfecher <jake@aztecprotocol.com>
Date: Tue, 8 Aug 2023 13:24:20 -0500
Subject: [PATCH] fix: Add foreign impl error (#2216)

Add foreign impl error
---
 .../noirc_evaluator/src/ssa/acir_gen/mod.rs   |  2 +-
 .../src/hir/def_collector/dc_crate.rs         | 21 +++++++++++++++----
 .../src/hir/def_collector/errors.rs           |  7 +++++++
 3 files changed, 25 insertions(+), 5 deletions(-)

diff --git a/crates/noirc_evaluator/src/ssa/acir_gen/mod.rs b/crates/noirc_evaluator/src/ssa/acir_gen/mod.rs
index aca809a85fa..7409a199641 100644
--- a/crates/noirc_evaluator/src/ssa/acir_gen/mod.rs
+++ b/crates/noirc_evaluator/src/ssa/acir_gen/mod.rs
@@ -1121,7 +1121,7 @@ impl Context {
 
 #[cfg(test)]
 mod tests {
-    use std::{rc::Rc, collections::HashMap};
+    use std::{collections::HashMap, rc::Rc};
 
     use acvm::{
         acir::{
diff --git a/crates/noirc_frontend/src/hir/def_collector/dc_crate.rs b/crates/noirc_frontend/src/hir/def_collector/dc_crate.rs
index 2beebf6871c..631f0cf86e4 100644
--- a/crates/noirc_frontend/src/hir/def_collector/dc_crate.rs
+++ b/crates/noirc_frontend/src/hir/def_collector/dc_crate.rs
@@ -13,7 +13,8 @@ use crate::hir::Context;
 use crate::node_interner::{FuncId, NodeInterner, StmtId, StructId, TypeAliasId};
 use crate::{
     ExpressionKind, Generics, Ident, LetStatement, Literal, NoirFunction, NoirStruct,
-    NoirTypeAlias, ParsedModule, Shared, Type, TypeBinding, UnresolvedGenerics, UnresolvedType,
+    NoirTypeAlias, ParsedModule, Shared, StructType, Type, TypeBinding, UnresolvedGenerics,
+    UnresolvedType,
 };
 use fm::FileId;
 use iter_extended::vecmap;
@@ -233,7 +234,19 @@ fn collect_impls(
 
             extend_errors(errors, unresolved.file_id, resolver.take_errors());
 
-            if let Some(type_module) = get_local_id_from_type(&typ) {
+            if let Some(struct_type) = get_struct_type(&typ) {
+                let struct_type = struct_type.borrow();
+                let type_module = struct_type.id.0.local_id;
+
+                // `impl`s are only allowed on types defined within the current crate
+                if struct_type.id.0.krate != crate_id {
+                    let span = *span;
+                    let type_name = struct_type.name.to_string();
+                    let error = DefCollectorErrorKind::ForeignImpl { span, type_name };
+                    errors.push(error.into_file_diagnostic(unresolved.file_id));
+                    continue;
+                }
+
                 // Grab the module defined by the struct type. Note that impls are a case
                 // where the module the methods are added to is not the same as the module
                 // they are resolved in.
@@ -258,9 +271,9 @@ fn collect_impls(
     }
 }
 
-fn get_local_id_from_type(typ: &Type) -> Option<LocalModuleId> {
+fn get_struct_type(typ: &Type) -> Option<&Shared<StructType>> {
     match typ {
-        Type::Struct(definition, _) => Some(definition.borrow().id.0.local_id),
+        Type::Struct(definition, _) => Some(definition),
         _ => None,
     }
 }
diff --git a/crates/noirc_frontend/src/hir/def_collector/errors.rs b/crates/noirc_frontend/src/hir/def_collector/errors.rs
index d18df58d64d..03f528020f8 100644
--- a/crates/noirc_frontend/src/hir/def_collector/errors.rs
+++ b/crates/noirc_frontend/src/hir/def_collector/errors.rs
@@ -22,6 +22,8 @@ pub enum DefCollectorErrorKind {
     PathResolutionError(PathResolutionError),
     #[error("Non-struct type used in impl")]
     NonStructTypeInImpl { span: Span },
+    #[error("Cannot `impl` a type defined outside the current crate")]
+    ForeignImpl { span: Span, type_name: String },
 }
 
 impl DefCollectorErrorKind {
@@ -101,6 +103,11 @@ impl From<DefCollectorErrorKind> for Diagnostic {
                 "Only struct types may have implementation methods".into(),
                 span,
             ),
+            DefCollectorErrorKind::ForeignImpl { span, type_name } => Diagnostic::simple_error(
+                "Cannot `impl` a type that was defined outside the current crate".into(),
+                format!("{type_name} was defined outside the current crate"),
+                span,
+            ),
         }
     }
 }