Add an error for trying to pass an array as vararg (#161)

src/typecheck.c

@@ -478,6 +478,13 @@ static const Type *typecheck_function_call(TypeContext *ctx, const AstCall *call
     for (int i = sig->nargs; i < call->nargs; i++) {
         // This code runs for varargs, e.g. the things to format in printf().
         ExpressionTypes *types = typecheck_expression_not_void(ctx, &call->args[i]);
+
+        if (types->type->kind == TYPE_ARRAY) {
+            fail_with_error(
+                call->args[i].location,
+                "arrays cannot be passed as varargs (try &array[0] instead of array)");
+        }
+
         if ((is_integer_type(types->type) && types->type->data.width_in_bits < 32)
             || types->type == boolType)
         {

tests/should_succeed/file.jou

@@ -37,7 +37,6 @@ def read_hello_123() -> void:
     rewind(f)
     text: byte[100]
     fgets(&text[0], 100, f)
-    # FIXME: crashes at runtime if you pass the array without &
     printf("got %s", &text[0])  # Output: got hello 123
 
     fclose(f)

tests/wrong_type/array_vararg.jou

@@ -0,0 +1,10 @@
+from "stdlib/io.jou" import printf
+
+def main() -> int:
+    s: byte[3]
+    s[0] = 'h'
+    s[1] = 'i'
+    s[2] = '\0'
+    printf("%s\n", &s[0])  # This works. No error
+    printf("%s\n", s)  # Error: arrays cannot be passed as varargs (try &array[0] instead of array)
+    return 0