Sum types redesign

proposals/pNNNN.md

@@ -0,0 +1,87 @@
+# Sum types redesign
+
+<!--
+Part of the Carbon Language project, under the Apache License v2.0 with LLVM
+Exceptions. See /LICENSE for license information.
+SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+-->
+
+[Pull request](https://github.com/carbon-language/carbon-lang/pull/####)
+
+<!-- toc -->
+
+## Table of contents
+
+-   [TODO: Initial proposal setup](#todo-initial-proposal-setup)
+-   [Abstract](#abstract)
+-   [Problem](#problem)
+-   [Background](#background)
+-   [Proposal](#proposal)
+-   [Details](#details)
+-   [Rationale](#rationale)
+-   [Alternatives considered](#alternatives-considered)
+
+<!-- tocstop -->
+
+## TODO: Initial proposal setup
+
+> TIP: Run `./new_proposal.py "TITLE"` to do new proposal setup.
+
+1. Copy this template to `new.md`, and create a commit.
+2. Create a GitHub pull request, to get a pull request number.
+    - Add the `proposal draft` label to the pull request.
+3. Rename `new.md` to `/proposals/p####.md`, where `####` should be the pull
+   request number.
+4. Update the title of the proposal (the `TODO` on line 1).
+5. Update the link to the pull request (the `####` on line 11).
+6. Delete this section.
+
+TODOs indicate where content should be updated for a proposal. See
+[Carbon Governance and Evolution](/docs/project/evolution.md) for more details.
+
+## Abstract
+
+TODO: Describe, in a succinct paragraph, the gist of this document. This
+paragraph should be reproduced verbatim in the PR summary.
+
+## Problem
+
+TODO: What problem are you trying to solve? How important is that problem? Who
+is impacted by it?
+
+## Background
+
+TODO: Is there any background that readers should consider to fully understand
+this problem and your approach to solving it?
+
+## Proposal
+
+TODO: Briefly and at a high level, how do you propose to solve the problem? Why
+will that in fact solve it?
+
+## Details
+
+TODO: Fully explain the details of the proposed solution.
+
+## Rationale
+
+TODO: How does this proposal effectively advance Carbon's goals? Rather than
+re-stating the full motivation, this should connect that motivation back to
+Carbon's stated goals and principles. This may evolve during review. Use links
+to appropriate sections of [`/docs/project/goals.md`](/docs/project/goals.md),
+and/or to documents in [`/docs/project/principles`](/docs/project/principles).
+For example:
+
+-   [Community and culture](/docs/project/goals.md#community-and-culture)
+-   [Language tools and ecosystem](/docs/project/goals.md#language-tools-and-ecosystem)
+-   [Performance-critical software](/docs/project/goals.md#performance-critical-software)
+-   [Software and language evolution](/docs/project/goals.md#software-and-language-evolution)
+-   [Code that is easy to read, understand, and write](/docs/project/goals.md#code-that-is-easy-to-read-understand-and-write)
+-   [Practical safety and testing mechanisms](/docs/project/goals.md#practical-safety-and-testing-mechanisms)
+-   [Fast and scalable development](/docs/project/goals.md#fast-and-scalable-development)
+-   [Modern OS platforms, hardware architectures, and environments](/docs/project/goals.md#modern-os-platforms-hardware-architectures-and-environments)
+-   [Interoperability with and migration from existing C++ code](/docs/project/goals.md#interoperability-with-and-migration-from-existing-c-code)
+
+## Alternatives considered
+
+TODO: What alternative solutions have you considered?