cmd/vet: clean up the test

- clean up the notypes version of the test so it's quiet
- change the package in the buildtag test to avoid confusing godoc

R=golang-dev, minux.ma, bradfitz
CC=golang-dev
https://golang.org/cl/8671049

src/cmd/vet/Makefile

@@ -5,8 +5,10 @@
 # Assumes go/types is installed
 test testshort:
 	go build -tags 'vet_test gotypes'
-	../../../test/errchk ./vet -printfuncs='Warn:1,Warnf:1' *.go *.s
+	../../../test/errchk ./vet -printfuncs='Warn:1,Warnf:1' test_*.go test_*.s
 
 test_notypes:
 	go build -tags 'vet_test'
-	../../../test/errchk ./vet -printfuncs='Warn:1,Warnf:1' *.go *.s
+	# Only those tests that do not depend on types.
+	# Excluded: test_print.go
+	../../../test/errchk ./vet -printfuncs='Warn:1,Warnf:1' test_asm.go test_assign.go test_atomic.go test_buildtag.go test_buildtag_bad.go test_deadcode.go test_method.go test_rangeloop.go test_structtag.go test_taglit.go test_*.s

src/cmd/vet/buildtag_bad.go → src/cmd/vet/test_buildtag_bad.go

@@ -8,4 +8,8 @@
 // +build @#$ // ERROR "invalid non-alphanumeric build constraint"
 
 // +build toolate // ERROR "build comment appears too late in file"
-package main
+package bad
+
+// This is package 'bad' rather than 'main' so the erroneous build
+// tag doesn't end up looking like a package doc for the vet command
+// when examined by godoc.