From 706b54bb85df2eb9a21da9e049fd1dff77342d25 Mon Sep 17 00:00:00 2001
From: Matthew Dempsky <mdempsky@google.com>
Date: Thu, 20 Dec 2018 11:10:06 -0800
Subject: [PATCH] cmd/compile: fix ICE due to bad rune width

It was possible that

    var X interface{} = 'x'

could cause a compilation failure due to having not calculated rune's
width yet. typecheck.go normally calculates the width of things, but
it doesn't for implicit conversions to default type. We already
compute the width of all of the standard numeric types in universe.go,
but we failed to calculate it for the rune alias type. So we could
later crash if the code never otherwise explicitly mentioned 'rune'.

While here, explicitly compute widths for 'byte' and 'error' for
consistency.

Fixes #29350.

Change-Id: Ifedd4899527c983ee5258dcf75aaf635b6f812f8
Reviewed-on: https://go-review.googlesource.com/c/155380
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Robert Griesemer <gri@golang.org>
---
 src/cmd/compile/internal/gc/universe.go | 3 +++
 test/fixedbugs/issue29350.go            | 9 +++++++++
 2 files changed, 12 insertions(+)
 create mode 100644 test/fixedbugs/issue29350.go

diff --git a/src/cmd/compile/internal/gc/universe.go b/src/cmd/compile/internal/gc/universe.go
index 745ce66bba2..104c6bab23d 100644
--- a/src/cmd/compile/internal/gc/universe.go
+++ b/src/cmd/compile/internal/gc/universe.go
@@ -386,6 +386,7 @@ func lexinit1() {
 	types.Errortype.Sym = s
 	types.Errortype.Orig = makeErrorInterface()
 	s.Def = asTypesNode(typenod(types.Errortype))
+	dowidth(types.Errortype)
 
 	// We create separate byte and rune types for better error messages
 	// rather than just creating type alias *types.Sym's for the uint8 and
@@ -401,6 +402,7 @@ func lexinit1() {
 	types.Bytetype.Sym = s
 	s.Def = asTypesNode(typenod(types.Bytetype))
 	asNode(s.Def).Name = new(Name)
+	dowidth(types.Bytetype)
 
 	// rune alias
 	s = builtinpkg.Lookup("rune")
@@ -408,6 +410,7 @@ func lexinit1() {
 	types.Runetype.Sym = s
 	s.Def = asTypesNode(typenod(types.Runetype))
 	asNode(s.Def).Name = new(Name)
+	dowidth(types.Runetype)
 
 	// backend-dependent builtin types (e.g. int).
 	for _, s := range typedefs {
diff --git a/test/fixedbugs/issue29350.go b/test/fixedbugs/issue29350.go
new file mode 100644
index 00000000000..9d59f6f6c0f
--- /dev/null
+++ b/test/fixedbugs/issue29350.go
@@ -0,0 +1,9 @@
+// compile
+
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+var X interface{} = 'x'