From 8433412b741e60f8a6f9608bcf81a6ce1a10a75e Mon Sep 17 00:00:00 2001
From: Alan Donovan <adonovan@google.com>
Date: Tue, 8 Apr 2025 14:12:00 -0400
Subject: [PATCH] go/types: document that Defs[id] may be missing in ill-typed
 code

Updates #70968

Change-Id: Id0a4acd6bad917ba8a5c439625bca14469b6eb7c
Reviewed-on: https://go-review.googlesource.com/c/go/+/663895
Auto-Submit: Alan Donovan <adonovan@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Commit-Queue: Alan Donovan <adonovan@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>
---
 src/go/types/api.go | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/go/types/api.go b/src/go/types/api.go
index beb2258c8b..f60c2ff7ee 100644
--- a/src/go/types/api.go
+++ b/src/go/types/api.go
@@ -254,6 +254,9 @@ type Info struct {
 	//
 	// For an embedded field, Defs returns the field *Var it defines.
 	//
+	// In ill-typed code, such as a duplicate declaration of the
+	// same name, Defs may lack an entry for a declaring identifier.
+	//
 	// Invariant: Defs[id] == nil || Defs[id].Pos() == id.Pos()
 	Defs map[*ast.Ident]Object