From 3b46e88734c5860965ef93f01be535095dd60257 Mon Sep 17 00:00:00 2001
From: James Shubin <james@shubin.ca>
Date: Wed, 11 Oct 2023 20:38:35 -0400
Subject: [PATCH] lang: types: Improve docs for New and initialize the list

If we use this to generate a zero value, we want to make sure it's
completely initialized in case we use it subsequently. We also improve
the docs at the same time.
---
 lang/types/type.go  | 6 +++++-
 lang/types/value.go | 1 +
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/lang/types/type.go b/lang/types/type.go
index 9461b1f9..aa72ca86 100644
--- a/lang/types/type.go
+++ b/lang/types/type.go
@@ -550,8 +550,12 @@ func NewType(s string) *Type {
 	return nil // error (this also matches the empty string as input)
 }
 
-// New creates a new Value of this type.
+// New creates a new Value of this type. It will represent the "zero" value. It
+// panics if you give it a malformed type.
 func (obj *Type) New() Value {
+	if obj == nil {
+		panic("malformed type")
+	}
 	switch obj.Kind {
 	case KindBool:
 		return NewBool()
diff --git a/lang/types/value.go b/lang/types/value.go
index 9281d974..1edd23e9 100644
--- a/lang/types/value.go
+++ b/lang/types/value.go
@@ -774,6 +774,7 @@ func NewList(t *Type) *ListValue {
 		return nil // sanity check
 	}
 	return &ListValue{
+		V: []Value{},
 		T: t,
 	}
 }