From d46a4b2d38729ea3a4deb43a8862eab7acb67bdc Mon Sep 17 00:00:00 2001
From: pca006132 <john.lck40@gmail.com>
Date: Thu, 12 Aug 2021 10:25:32 +0800
Subject: [PATCH] symbol_resolver: fixed type variable handling

---
 nac3core/src/symbol_resolver.rs               | 63 ++++++++++++-------
 .../src/typecheck/type_inferencer/test.rs     |  4 +-
 2 files changed, 42 insertions(+), 25 deletions(-)

diff --git a/nac3core/src/symbol_resolver.rs b/nac3core/src/symbol_resolver.rs
index aa01c7dc..b6e3b792 100644
--- a/nac3core/src/symbol_resolver.rs
+++ b/nac3core/src/symbol_resolver.rs
@@ -22,19 +22,22 @@ pub enum SymbolValue {
 }
 
 pub trait SymbolResolver {
+    // get type of type variable identifier or top-level function type
     fn get_symbol_type(
         &self,
         unifier: &mut Unifier,
         primitives: &PrimitiveStore,
         str: &str,
     ) -> Option<Type>;
-    fn get_identifier_def(&self, str: &str) -> DefinitionId;
+    // get the top-level definition of identifiers
+    fn get_identifier_def(&self, str: &str) -> Option<DefinitionId>;
     fn get_symbol_value(&self, str: &str) -> Option<SymbolValue>;
     fn get_symbol_location(&self, str: &str) -> Option<Location>;
     // handle function call etc.
 }
 
 impl dyn SymbolResolver {
+    // convert type annotation into type
     pub fn parse_type_annotation<T>(
         &self,
         top_level: &TopLevelContext,
@@ -52,29 +55,41 @@ impl dyn SymbolResolver {
                 "None" => Ok(primitives.none),
                 x => {
                     let obj_id = self.get_identifier_def(x);
-                    let defs = top_level.definitions.read();
-                    let def = defs[obj_id.0].read();
-                    if let TopLevelDef::Class { fields, methods, type_vars, .. } = &*def {
-                        if !type_vars.is_empty() {
-                            return Err(format!(
-                                "Unexpected number of type parameters: expected {} but got 0",
-                                type_vars.len()
-                            ));
+                    if let Some(obj_id) = obj_id {
+                        let defs = top_level.definitions.read();
+                        let def = defs[obj_id.0].read();
+                        if let TopLevelDef::Class { fields, methods, type_vars, .. } = &*def {
+                            if !type_vars.is_empty() {
+                                return Err(format!(
+                                    "Unexpected number of type parameters: expected {} but got 0",
+                                    type_vars.len()
+                                ));
+                            }
+                            let fields = RefCell::new(
+                                chain(
+                                    fields.iter().map(|(k, v)| (k.clone(), *v)),
+                                    methods.iter().map(|(k, v, _)| (k.clone(), *v)),
+                                )
+                                .collect(),
+                            );
+                            Ok(unifier.add_ty(TypeEnum::TObj {
+                                obj_id,
+                                fields,
+                                params: Default::default(),
+                            }))
+                        } else {
+                            Err("Cannot use function name as type".into())
                         }
-                        let fields = RefCell::new(
-                            chain(
-                                fields.iter().map(|(k, v)| (k.clone(), *v)),
-                                methods.iter().map(|(k, v, _)| (k.clone(), *v)),
-                            )
-                            .collect(),
-                        );
-                        Ok(unifier.add_ty(TypeEnum::TObj {
-                            obj_id,
-                            fields,
-                            params: Default::default(),
-                        }))
                     } else {
-                        Err("Cannot use function name as type".into())
+                        // it could be a type variable
+                        let ty = self
+                            .get_symbol_type(unifier, primitives, x)
+                            .ok_or_else(|| "Cannot use function name as type".to_owned())?;
+                        if let TypeEnum::TVar { .. } = &*unifier.get_ty(ty) {
+                            Ok(ty)
+                        } else {
+                            Err(format!("Unknown type annotation {}", x))
+                        }
                     }
                 }
             },
@@ -95,7 +110,9 @@ impl dyn SymbolResolver {
                             vec![self.parse_type_annotation(top_level, unifier, primitives, slice)?]
                         };
 
-                        let obj_id = self.get_identifier_def(id);
+                        let obj_id = self
+                            .get_identifier_def(id)
+                            .ok_or_else(|| format!("Unknown type annotation {}", id))?;
                         let defs = top_level.definitions.read();
                         let def = defs[obj_id.0].read();
                         if let TopLevelDef::Class { fields, methods, type_vars, .. } = &*def {
diff --git a/nac3core/src/typecheck/type_inferencer/test.rs b/nac3core/src/typecheck/type_inferencer/test.rs
index 8fbd88f9..ee65dbe3 100644
--- a/nac3core/src/typecheck/type_inferencer/test.rs
+++ b/nac3core/src/typecheck/type_inferencer/test.rs
@@ -28,8 +28,8 @@ impl SymbolResolver for Resolver {
         unimplemented!()
     }
 
-    fn get_identifier_def(&self, id: &str) -> DefinitionId {
-        self.id_to_def.get(id).cloned().unwrap()
+    fn get_identifier_def(&self, id: &str) -> Option<DefinitionId> {
+        self.id_to_def.get(id).cloned()
     }
 }