cmd/doc: fix strange indentation artifacts with unexported fields

The NamePos value was not being set, and would default to a value
of zero. This would cause the printing logic to get confused as
to where exactly to place the "Has unexported fields" string.

A trivial package changes from

<
type A struct {
	A int // A
	B int
			// B
	// Has unexported fields.
}
>

to

<
type A struct {
	A int // A
	B int // B
	// Has unexported fields.
}
>

Fixes #12971

Change-Id: I53b7799a1f1c0ad7dcaddff83d9aaeb1d6b7823e
Reviewed-on: https://go-review.googlesource.com/16286
Run-TryBot: Joe Tsai <joetsai@digital-static.net>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rob Pike <r@golang.org>

1 files changed, 8 insertions, 1 deletions

diff --git a/src/cmd/doc/testdata/pkg.go b/src/cmd/doc/testdata/pkg.go
index 0f06651d6b..3e7acee50b 100644
--- a/src/cmd/doc/testdata/pkg.go
+++ b/src/cmd/doc/testdata/pkg.go
@@ -60,7 +60,7 @@ func internalFunc(a int) bool
 // Comment about exported type.
 type ExportedType struct {
 	// Comment before exported field.
-	ExportedField   int
+	ExportedField   int // Comment on line with exported field.
 	unexportedField int // Comment on line with unexported field.
 }
 
@@ -87,6 +87,13 @@ func ExportedTypeConstructor() *ExportedType {
 
 const unexportedTypedConstant ExportedType = 1 // In a separate section to test -u.
 
+// Comment about exported interface.
+type ExportedInterface interface {
+	// Comment before exported method.
+	ExportedMethod()   // Comment on line with exported method.
+	unexportedMethod() // Comment on line with unexported method.
+}
+
 // Comment about unexported type.
 type unexportedType int