Add staticcheck and fix issues (#79)

This adds `staticcheck` to `make lint` and fixes issues found by it.
diff --git a/Makefile b/Makefile
index 7248fae..1b1376d 100644
--- a/Makefile
+++ b/Makefile
@@ -4,6 +4,7 @@
 GOLINT = $(GOBIN)/golint
 GEN_ATOMICINT = $(GOBIN)/gen-atomicint
 GEN_ATOMICWRAPPER = $(GOBIN)/gen-atomicwrapper
+STATICCHECK = $(GOBIN)/staticcheck
 
 GO_FILES ?= $(shell find . '(' -path .git -o -path vendor ')' -prune -o -name '*.go' -print)
 
@@ -29,6 +30,9 @@
 $(GOLINT):
 	cd tools && go install golang.org/x/lint/golint
 
+$(STATICCHECK):
+	cd tools && go install honnef.co/go/tools/cmd/staticcheck
+
 $(GEN_ATOMICWRAPPER): $(wildcard ./internal/gen-atomicwrapper/*)
 	go build -o $@ ./internal/gen-atomicwrapper
 
@@ -39,8 +43,12 @@
 golint: $(GOLINT)
 	$(GOLINT) ./...
 
+.PHONY: staticcheck
+staticcheck: $(STATICCHECK)
+	$(STATICCHECK) ./...
+
 .PHONY: lint
-lint: gofmt golint generatenodirty
+lint: gofmt golint staticcheck generatenodirty
 
 # comma separated list of packages to consider for code coverage.
 COVER_PKG = $(shell \
diff --git a/bool.go b/bool.go
index 1bf3fa0..9cf1914 100644
--- a/bool.go
+++ b/bool.go
@@ -28,7 +28,7 @@
 
 // Bool is an atomic type-safe wrapper for bool values.
 type Bool struct {
-	nocmp // disallow non-atomic comparison
+	_ nocmp // disallow non-atomic comparison
 
 	v Uint32
 }
diff --git a/duration.go b/duration.go
index 30ed6aa..027cfcb 100644
--- a/duration.go
+++ b/duration.go
@@ -29,7 +29,7 @@
 
 // Duration is an atomic type-safe wrapper for time.Duration values.
 type Duration struct {
-	nocmp // disallow non-atomic comparison
+	_ nocmp // disallow non-atomic comparison
 
 	v Int64
 }
diff --git a/error.go b/error.go
index cedbc91..a6166fb 100644
--- a/error.go
+++ b/error.go
@@ -24,7 +24,7 @@
 
 // Error is an atomic type-safe wrapper for error values.
 type Error struct {
-	nocmp // disallow non-atomic comparison
+	_ nocmp // disallow non-atomic comparison
 
 	v Value
 }
diff --git a/float64.go b/float64.go
index fb33e90..0719060 100644
--- a/float64.go
+++ b/float64.go
@@ -29,7 +29,7 @@
 
 // Float64 is an atomic type-safe wrapper for float64 values.
 type Float64 struct {
-	nocmp // disallow non-atomic comparison
+	_ nocmp // disallow non-atomic comparison
 
 	v Uint64
 }
diff --git a/int32.go b/int32.go
index 357f178..18ae564 100644
--- a/int32.go
+++ b/int32.go
@@ -30,7 +30,7 @@
 
 // Int32 is an atomic wrapper around int32.
 type Int32 struct {
-	nocmp // disallow non-atomic comparison
+	_ nocmp // disallow non-atomic comparison
 
 	v int32
 }
diff --git a/int64.go b/int64.go
index 8448018..2bcbbfa 100644
--- a/int64.go
+++ b/int64.go
@@ -30,7 +30,7 @@
 
 // Int64 is an atomic wrapper around int64.
 type Int64 struct {
-	nocmp // disallow non-atomic comparison
+	_ nocmp // disallow non-atomic comparison
 
 	v int64
 }
diff --git a/internal/gen-atomicint/main.go b/internal/gen-atomicint/main.go
index 4ffcb94..211cd34 100644
--- a/internal/gen-atomicint/main.go
+++ b/internal/gen-atomicint/main.go
@@ -135,7 +135,7 @@
 
 // {{ .Name }} is an atomic wrapper around {{ .Wrapped }}.
 type {{ .Name }} struct {
-	nocmp // disallow non-atomic comparison
+	_ nocmp // disallow non-atomic comparison
 
 	v {{ .Wrapped }}
 }
diff --git a/internal/gen-atomicwrapper/main.go b/internal/gen-atomicwrapper/main.go
index 0bb180e..862c411 100644
--- a/internal/gen-atomicwrapper/main.go
+++ b/internal/gen-atomicwrapper/main.go
@@ -227,7 +227,7 @@
 
 // {{ .Name }} is an atomic type-safe wrapper for {{ .Type }} values.
 type {{ .Name }} struct{
-	nocmp // disallow non-atomic comparison
+	_ nocmp // disallow non-atomic comparison
 
 	v {{ .Wrapped }}
 }
diff --git a/nocmp_test.go b/nocmp_test.go
index 22a7e02..d4be166 100644
--- a/nocmp_test.go
+++ b/nocmp_test.go
@@ -77,17 +77,16 @@
 
 // nocmp must not add to the size of a struct in-memory.
 func TestNocmpSize(t *testing.T) {
-	type x struct{ i int }
+	type x struct{ _ int }
 
 	before := reflect.TypeOf(x{}).Size()
 
 	type y struct {
-		nocmp
-
-		x x
+		_ nocmp
+		_ x
 	}
 
-	after := reflect.TypeOf(x{}).Size()
+	after := reflect.TypeOf(y{}).Size()
 
 	assert.Equal(t, before, after,
 		"expected nocmp to have no effect on struct size")
@@ -100,7 +99,7 @@
 //   var x atomic.Int32
 //   x = atomic.NewInt32(1)
 func TestNocmpCopy(t *testing.T) {
-	type foo struct{ nocmp }
+	type foo struct{ _ nocmp }
 
 	t.Run("struct copy", func(t *testing.T) {
 		a := foo{}
diff --git a/stress_test.go b/stress_test.go
index 3dc7852..da9969b 100644
--- a/stress_test.go
+++ b/stress_test.go
@@ -37,7 +37,7 @@
 var _stressTests = map[string]func() func(){
 	"i32/std":  stressStdInt32,
 	"i32":      stressInt32,
-	"i64/std":  stressStdInt32,
+	"i64/std":  stressStdInt64,
 	"i64":      stressInt64,
 	"u32/std":  stressStdUint32,
 	"u32":      stressUint32,
diff --git a/string.go b/string.go
index 8e3ac35..225b7a2 100644
--- a/string.go
+++ b/string.go
@@ -24,7 +24,7 @@
 
 // String is an atomic type-safe wrapper for string values.
 type String struct {
-	nocmp // disallow non-atomic comparison
+	_ nocmp // disallow non-atomic comparison
 
 	v Value
 }
diff --git a/tools/go.mod b/tools/go.mod
index c7c0fc4..6bc16f2 100644
--- a/tools/go.mod
+++ b/tools/go.mod
@@ -2,7 +2,7 @@
 
 require (
 	golang.org/x/lint v0.0.0-20190930215403-16217165b5de
-	golang.org/x/tools v0.0.0-20191029041327-9cc4af7d6b2c // indirect
+	honnef.co/go/tools v0.0.1-2020.1.5
 )
 
 go 1.13
diff --git a/tools/go.sum b/tools/go.sum
index f9e4a2f..5c151b4 100644
--- a/tools/go.sum
+++ b/tools/go.sum
@@ -1,12 +1,28 @@
+github.com/BurntSushi/toml v0.3.1 h1:WXkYYl6Yr3qBf1K79EBnL4mak0OimBfB0XUf9Vl28OQ=
+github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
+github.com/google/renameio v0.1.0/go.mod h1:KWCgfxg9yswjAJkECMjeO8J8rahYeXnNhOm40UhjYkI=
+github.com/kisielk/gotool v1.0.0/go.mod h1:XhKaO+MFFWcvkIS/tQcRk01m1F5IRFswLeQ+oQHNcck=
+github.com/kr/pretty v0.1.0/go.mod h1:dAy3ld7l9f0ibDNOQOHHMYYIIbhfbHSm3C4ZsoJORNo=
+github.com/kr/pty v1.1.1/go.mod h1:pFQYn66WHrOpPYNljwOMqo10TkYh1fy3cYio2l3bCsQ=
+github.com/kr/text v0.1.0/go.mod h1:4Jbv+DJW3UT/LiOwJeYQe1efqtUx/iVham/4vfdArNI=
+github.com/rogpeppe/go-internal v1.3.0/go.mod h1:M8bDsm7K2OlrFYOpmOWEs/qY81heoFRclV5y23lUDJ4=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
+golang.org/x/crypto v0.0.0-20190510104115-cbcb75029529/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
 golang.org/x/lint v0.0.0-20190930215403-16217165b5de h1:5hukYrvBGR8/eNkX5mdUezrA6JiaEZDtJb9Ei+1LlBs=
 golang.org/x/lint v0.0.0-20190930215403-16217165b5de/go.mod h1:6SW0HCj/g11FgYtHlgUYUwCkIfeOF89ocIRzGO/8vkc=
+golang.org/x/mod v0.0.0-20190513183733-4bf6d317e70e/go.mod h1:mXi4GBBbnImb6dmsKGUJ2LatrhH/nqhxcFungHvyanc=
 golang.org/x/net v0.0.0-20190311183353-d8887717615a/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
+golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
 golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
 golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
+golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/tools v0.0.0-20190311212946-11955173bddd/go.mod h1:LCzVGOaR6xXOjkQ3onu1FJEFr0SW1gC7cKk1uF8kGRs=
-golang.org/x/tools v0.0.0-20191029041327-9cc4af7d6b2c h1:IGkKhmfzcztjm6gYkykvu/NiS8kaqbCWAEWWAyf8J5U=
-golang.org/x/tools v0.0.0-20191029041327-9cc4af7d6b2c/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
+golang.org/x/tools v0.0.0-20191130070609-6e064ea0cf2d h1:/iIZNFGxc/a7C3yWjGcnboV+Tkc7mxr+p6fDztwoxuM=
+golang.org/x/tools v0.0.0-20191130070609-6e064ea0cf2d/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
 golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
+gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/errgo.v2 v2.1.0/go.mod h1:hNsd1EY+bozCKY1Ytp96fpM3vjJbqLJn88ws8XvfDNI=
+honnef.co/go/tools v0.0.1-2020.1.5 h1:nI5egYTGJakVyOryqLs1cQO5dO0ksin5XXs2pspk75k=
+honnef.co/go/tools v0.0.1-2020.1.5/go.mod h1:X/FiERA/W4tHapMX5mGpAtMSVEeEUOyHaw9vFzvIQ3k=
diff --git a/tools/tools.go b/tools/tools.go
index 3ddca55..b4b3a01 100644
--- a/tools/tools.go
+++ b/tools/tools.go
@@ -25,4 +25,5 @@
 import (
 	// Tools used during development.
 	_ "golang.org/x/lint/golint"
+	_ "honnef.co/go/tools/cmd/staticcheck"
 )
diff --git a/uint32.go b/uint32.go
index 3fbb696..a973aba 100644
--- a/uint32.go
+++ b/uint32.go
@@ -30,7 +30,7 @@
 
 // Uint32 is an atomic wrapper around uint32.
 type Uint32 struct {
-	nocmp // disallow non-atomic comparison
+	_ nocmp // disallow non-atomic comparison
 
 	v uint32
 }
diff --git a/uint64.go b/uint64.go
index 7cec96b..3b6c71f 100644
--- a/uint64.go
+++ b/uint64.go
@@ -30,7 +30,7 @@
 
 // Uint64 is an atomic wrapper around uint64.
 type Uint64 struct {
-	nocmp // disallow non-atomic comparison
+	_ nocmp // disallow non-atomic comparison
 
 	v uint64
 }
diff --git a/value.go b/value.go
index 5c32903..671f3a3 100644
--- a/value.go
+++ b/value.go
@@ -25,6 +25,7 @@
 // Value shadows the type of the same name from sync/atomic
 // https://godoc.org/sync/atomic#Value
 type Value struct {
-	nocmp // disallow non-atomic comparison
 	atomic.Value
+
+	_ nocmp // disallow non-atomic comparison
 }