From 26365e4e90c98f4b41230c50615e3a856598c66a Mon Sep 17 00:00:00 2001
From: Rob Pike <r@golang.org>
Date: Mon, 16 Mar 2015 14:52:01 -0700
Subject: [PATCH] cmd/cover: fix handling of empty type switch

Just missed a case (ha!) in the tree walk. Dup the code for an empty switch, add test.

Fixes #10163.

Change-Id: I3d50ab6cb450ca21e87213291eaab8cbe924fac5
Reviewed-on: https://go-review.googlesource.com/7641
Reviewed-by: Andrew Gerrand <adg@golang.org>
---
 cmd/cover/cover.go         |  5 +++++
 cmd/cover/testdata/test.go | 18 ++++++++++++++++++
 2 files changed, 23 insertions(+)

diff --git a/cmd/cover/cover.go b/cmd/cover/cover.go
index 3aaf246f..ceaf3cfa 100644
--- a/cmd/cover/cover.go
+++ b/cmd/cover/cover.go
@@ -220,6 +220,11 @@ func (f *File) Visit(node ast.Node) ast.Visitor {
 		if n.Body == nil || len(n.Body.List) == 0 {
 			return nil
 		}
+	case *ast.TypeSwitchStmt:
+		// Don't annotate an empty type switch - creates a syntax error.
+		if n.Body == nil || len(n.Body.List) == 0 {
+			return nil
+		}
 	}
 	return f
 }
diff --git a/cmd/cover/testdata/test.go b/cmd/cover/testdata/test.go
index 80b1f6b1..167a341c 100644
--- a/cmd/cover/testdata/test.go
+++ b/cmd/cover/testdata/test.go
@@ -22,6 +22,7 @@ func testAll() {
 	testTypeSwitch()
 	testSelect1()
 	testSelect2()
+	testEmptySwitches()
 }
 
 func testSimple() {
@@ -175,3 +176,20 @@ func testSelect2() {
 		}
 	}
 }
+
+// Empty control statements created syntax errors. This function
+// is here just to be sure that those are handled correctly now.
+func testEmptySwitches() {
+	check(LINE, 1)
+	switch 3 {
+	}
+	check(LINE, 1)
+	switch i := (interface{})(3).(int); i {
+	}
+	check(LINE, 1)
+	go func() {
+		check(LINE, 1)
+		select {}
+	}()
+	check(LINE, 1)
+}