From 51bf126a32a02d91feb31a1b00db46066e906e39 Mon Sep 17 00:00:00 2001
From: David Mak <chmakac@connect.ust.hk>
Date: Sat, 5 Oct 2024 15:57:51 +0800
Subject: [PATCH] [core] typecheck/type_inferencer: Differentiate global
 symbols

Required for analyzing use of global symbols before global declaration.
---
 nac3core/src/typecheck/function_check.rs      | 12 ++++++----
 nac3core/src/typecheck/type_inferencer/mod.rs | 24 +++++++++++++++++--
 2 files changed, 30 insertions(+), 6 deletions(-)

diff --git a/nac3core/src/typecheck/function_check.rs b/nac3core/src/typecheck/function_check.rs
index 0f38a341..c4626f2f 100644
--- a/nac3core/src/typecheck/function_check.rs
+++ b/nac3core/src/typecheck/function_check.rs
@@ -10,7 +10,7 @@ use nac3parser::ast::{
 };
 
 use super::{
-    type_inferencer::{IdentifierInfo, Inferencer},
+    type_inferencer::{DeclarationSource, IdentifierInfo, Inferencer},
     typedef::{Type, TypeEnum},
 };
 use crate::toplevel::helper::PrimDef;
@@ -368,7 +368,7 @@ impl<'a> Inferencer<'a> {
             StmtKind::Global { names, .. } => {
                 for id in names {
                     if let Some(id_info) = defined_identifiers.get(id) {
-                        if !id_info.is_global {
+                        if id_info.source == DeclarationSource::Local {
                             return Err(HashSet::from([format!(
                                 "name '{id}' is assigned to before global declaration at {}",
                                 stmt.location,
@@ -385,8 +385,12 @@ impl<'a> Inferencer<'a> {
                         *id,
                     ) {
                         Ok(_) => {
-                            self.defined_identifiers
-                                .insert(*id, IdentifierInfo { is_global: true });
+                            self.defined_identifiers.insert(
+                                *id,
+                                IdentifierInfo {
+                                    source: DeclarationSource::Global { is_explicit: Some(true) },
+                                },
+                            );
                         }
                         Err(e) => {
                             return Err(HashSet::from([format!(
diff --git a/nac3core/src/typecheck/type_inferencer/mod.rs b/nac3core/src/typecheck/type_inferencer/mod.rs
index ce2e76d2..dde45d79 100644
--- a/nac3core/src/typecheck/type_inferencer/mod.rs
+++ b/nac3core/src/typecheck/type_inferencer/mod.rs
@@ -88,11 +88,31 @@ impl PrimitiveStore {
     }
 }
 
+/// The location where an identifier declaration refers to.
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub enum DeclarationSource {
+    /// Local scope.
+    Local,
+
+    /// Global scope.
+    Global {
+        /// Whether the identifier is declared by the use of `global` statement. This field is
+        /// [`None`] if the identifier does not refer to a variable.
+        is_explicit: Option<bool>,
+    },
+}
+
 /// Information regarding a defined identifier.
-#[derive(Clone, Copy, Debug, Default)]
+#[derive(Clone, Copy, Debug)]
 pub struct IdentifierInfo {
     /// Whether this identifier refers to a global variable.
-    pub is_global: bool,
+    pub source: DeclarationSource,
+}
+
+impl Default for IdentifierInfo {
+    fn default() -> Self {
+        IdentifierInfo { source: DeclarationSource::Local }
+    }
 }
 
 impl IdentifierInfo {