From e326af38f85f9b186997bdc36842f7c08ca62614 Mon Sep 17 00:00:00 2001
From: Sage Vaillancourt <sagev9000@tutanota.com>
Date: Wed, 13 Apr 2022 16:57:06 -0400
Subject: [PATCH] Allow number indexing of struct fields.

Better error messages on failed struct access.
---
 src/pebblisp.c | 17 +++++++++++++----
 src/pebblisp.h |  2 +-
 2 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/src/pebblisp.c b/src/pebblisp.c
index 4ccf682..e02a695 100644
--- a/src/pebblisp.c
+++ b/src/pebblisp.c
@@ -307,13 +307,22 @@ Object structAccess(Object* params, unused int length, unused struct Environment
     Object field = params[1];
 
     struct StructDef* structDef = getStructAt(structo.structObject->definition);
-    for (int i = 0; i < structDef->fieldCount; i++) {
-        if (strcmp(field.string, structDef->names[i]) == 0) {
-            return cloneObject(structo.structObject->fields[i]);
+    if (isStringy(field)) {
+        for (int i = 0; i < structDef->fieldCount; i++) {
+            if (strcmp(field.string, structDef->names[i]) == 0) {
+                return cloneObject(structo.structObject->fields[i]);
+            }
         }
+        throw(NULL_PARSE, "Could not find struct field named `%s`", field.string);
+    }
+    if (isNumber(field)) {
+        if (structDef->fieldCount < field.number || field.number < 0) {
+            throw(NULL_PARSE, "Could not find struct field at index %ld. Struct `%s` has %d fields.", field.number, structDef->name, structDef->fieldCount);
+        }
+        return cloneObject(structo.structObject->fields[field.number]);
     }
 
-    throw(NULL_PARSE, "Could not find field named `%s`", field.string);
+    throw(BAD_PARAMS, "Struct fields should be indexed with a string or a number, but received a %s", getTypeName(&field));
 }
 
 Result parse(struct Slice* slices)
diff --git a/src/pebblisp.h b/src/pebblisp.h
index fefad61..079992e 100644
--- a/src/pebblisp.h
+++ b/src/pebblisp.h
@@ -122,7 +122,7 @@ fn(def, "def",
 );
 
 tfn(structAccess, "poss",
-    ({ expect(isStruct), expect(isStringy), anyType }),
+    ({ expect(isStruct), anyType, anyType }),
     "Get the value of a struct's field",
     "(struct Post (title body))\n    "
     "(def p (Post \"This is a title\" \"This is the body\"))\n      "