From 3821eaa48ca56791cb5c9b85da70dde052d6c7ef Mon Sep 17 00:00:00 2001
From: Bad Diode <bd@badd10de.dev>
Date: Wed, 10 Nov 2021 18:16:34 +0100
Subject: Add support for accessing procedure parameters

---
 src/compiler.h | 17 ++++++++++++++---
 src/parser.c   | 28 +++++++++++++++++++++++-----
 src/parser.h   |  1 +
 3 files changed, 38 insertions(+), 8 deletions(-)

diff --git a/src/compiler.h b/src/compiler.h
index 14c6954..2a44220 100644
--- a/src/compiler.h
+++ b/src/compiler.h
@@ -515,7 +515,7 @@ void
 compile_def(Object *obj) {
     context_printf("    ;; --> compile_def\n");
     compile_object(obj->var_expr);
-    ssize_t idx = find_local_index(current_env->locals, obj->var_name);
+    ssize_t idx = find_var_index(current_env->locals, obj->var_name);
     context_printf("    pop     rax\n");
     context_printf("    mov     [rbp + %ld], rax\n", 8 * idx);
     compile_nil();
@@ -525,8 +525,19 @@ compile_def(Object *obj) {
 void
 compile_symbol(Object *obj) {
     context_printf("    ;; --> compile_symbol\n");
-    ssize_t idx = find_local_index(current_env->locals, obj);
-    context_printf("    mov     rax, [rbp + %ld]\n", 8 * idx);
+    ssize_t idx = find_var_index(current_env->locals, obj);
+    if (idx != -1) {
+        context_printf("    mov     rax, [rbp + %ld]\n", 8 * idx);
+        context_printf("    push    rax\n");
+        context_printf("    ;; <-- compile_symbol\n");
+        return;
+    }
+    idx = find_var_index(current_env->params, obj);
+    assert(idx != -1 && "unexpected index");
+    size_t n_locals = array_size(current_env->locals);
+    size_t n_params = array_size(current_env->params);
+    size_t offset = 8 * (n_locals + n_params - idx + 1);
+    context_printf("    mov     rax, [rbp + %ld]\n", offset);
     context_printf("    push    rax\n");
     context_printf("    ;; <-- compile_symbol\n");
 }
diff --git a/src/parser.c b/src/parser.c
index 2bf95d4..5bb7393 100644
--- a/src/parser.c
+++ b/src/parser.c
@@ -429,9 +429,9 @@ parse_tree(Parser *parser, Errors *errors) {
 }
 
 ssize_t
-find_local_index(Object **locals, Object *symbol) {
-    for (size_t i = 0; i < array_size(locals); i++) {
-        if (object_equal(locals[i], symbol)) {
+find_var_index(Object **vars, Object *symbol) {
+    for (size_t i = 0; i < array_size(vars); i++) {
+        if (object_equal(vars[i], symbol)) {
             return i;
         }
     }
@@ -441,10 +441,14 @@ find_local_index(Object **locals, Object *symbol) {
 Object *
 symbol_in_env(Environment *env, Object *symbol) {
     while (env != NULL) {
-        ssize_t idx = find_local_index(env->locals, symbol);
+        ssize_t idx = find_var_index(env->locals, symbol);
         if (idx != -1) {
             return env->locals[idx];
         }
+        idx = find_var_index(env->params, symbol);
+        if (idx != -1) {
+            return env->params[idx];
+        }
         env = env->parent;
     }
     return NULL;
@@ -452,12 +456,20 @@ symbol_in_env(Environment *env, Object *symbol) {
 
 void
 insert_local(Environment *env, Object *symbol) {
-    if (find_local_index(env->locals, symbol) != -1) {
+    if (find_var_index(env->locals, symbol) != -1) {
         return;
     }
     array_push(env->locals, symbol);
 }
 
+void
+insert_params(Environment *env, Object *symbol) {
+    if (find_var_index(env->params, symbol) != -1) {
+        return;
+    }
+    array_push(env->params, symbol);
+}
+
 void
 semantic_analysis(Environment *env, Object *obj, Errors *errors) {
     if (obj == NULL || obj->visited) {
@@ -523,6 +535,9 @@ semantic_analysis(Environment *env, Object *obj, Errors *errors) {
             // Initialize scope for this lambda.
             Environment *new_env = env_alloc(env);
             obj->env = new_env;
+            for (size_t i = 0; i < array_size(obj->params); i++) {
+                insert_params(obj->env, obj->params[i]);
+            }
             // Used for removing unnecessary statements.
             Object **new_body = NULL;
             array_init(new_body, 0);
@@ -622,7 +637,9 @@ Environment *
 env_alloc(Environment *parent) {
     Environment *env = malloc(sizeof(Environment));
     env->locals = NULL;
+    env->params = NULL;
     array_init(env->locals, 0);
+    array_init(env->params, 0);
     env->parent = parent;
     array_push(environments, env);
     return env;
@@ -663,6 +680,7 @@ free_objects(void) {
         for (size_t i = 0; i < array_size(environments); i++) {
             Environment *env = environments[i];
             array_free(env->locals);
+            array_free(env->params);
             free(env);
         }
         array_free(environments);
diff --git a/src/parser.h b/src/parser.h
index c117c61..2c5cb61 100644
--- a/src/parser.h
+++ b/src/parser.h
@@ -5,6 +5,7 @@
 
 typedef struct Environment {
     struct Object **locals;
+    struct Object **params;
     struct Environment *parent;
 } Environment;
 
-- 
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