From f7d403c35849758d68e3a0ca9a9777bfce7da0b7 Mon Sep 17 00:00:00 2001
From: Bruce Hill <bruce@bruce-hill.com>
Date: Sun, 25 Feb 2024 13:04:35 -0500
Subject: WIP on stackrefs

---
 typecheck.c | 29 ++++++++++++++++++++++++++++-
 1 file changed, 28 insertions(+), 1 deletion(-)

(limited to 'typecheck.c')

diff --git a/typecheck.c b/typecheck.c
index ce3c9d08..a5153512 100644
--- a/typecheck.c
+++ b/typecheck.c
@@ -203,6 +203,7 @@ type_t *get_type(env_t *env, ast_t *ast)
         ast_t *value = Match(ast, StackReference)->value;
         type_t *pointed_t = get_type(env, Match(ast, StackReference)->value);
         bool is_stack = true;
+        bool is_readonly = !can_be_mutated(env, value);
         // References to heap members/indexes are heap pointers, e.g. v := @Vec{1,2}; &v.x
         switch (value->tag) {
         case FieldAccess: {
@@ -217,7 +218,7 @@ type_t *get_type(env_t *env, ast_t *ast)
         }
         default: break;
         }
-        return Type(PointerType, .pointed=pointed_t, .is_stack=is_stack);
+        return Type(PointerType, .pointed=pointed_t, .is_stack=is_stack, .is_readonly=is_readonly);
     }
     case StringJoin: case StringLiteral: {
         return Type(StringType);
@@ -711,4 +712,30 @@ type_t *get_arg_type(env_t *env, arg_t *arg)
     return get_type(env, arg->default_val);
 }
 
+bool can_be_mutated(env_t *env, ast_t *ast)
+{
+    switch (ast->tag) {
+    case Var: return true;
+    case FieldAccess: {
+        auto access = Match(ast, FieldAccess);
+        type_t *fielded_type = get_type(env, access->fielded);
+        if (fielded_type->tag == PointerType) {
+            auto ptr = Match(fielded_type, PointerType);
+            return !ptr->is_readonly;
+        }
+        return can_be_mutated(env, access->fielded);
+    }
+    case Index: {
+        auto index = Match(ast, Index);
+        type_t *indexed_type = get_type(env, index->indexed);
+        if (indexed_type->tag == PointerType) {
+            auto ptr = Match(indexed_type, PointerType);
+            return !ptr->is_readonly;
+        }
+        return false;
+    }
+    default: return false;
+    }
+}
+
 // vim: ts=4 sw=0 et cino=L2,l1,(0,W4,m1,\:0
-- 
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