Remove unused check.Checker argument
diff --git a/internal/cgen/cgen.go b/internal/cgen/cgen.go
index b83454e..ea572f7 100644
--- a/internal/cgen/cgen.go
+++ b/internal/cgen/cgen.go
@@ -28,7 +28,6 @@
 	"strings"
 
 	"github.com/google/wuffs/lang/builtin"
-	"github.com/google/wuffs/lang/check"
 	"github.com/google/wuffs/lang/generate"
 
 	cf "github.com/google/wuffs/cmd/commonflags"
@@ -105,7 +104,7 @@
 	cformatterFlag := flags.String("cformatter", cf.CformatterDefault, cf.CformatterUsage)
 	genlinenumFlag := flags.Bool("genlinenum", cf.GenlinenumDefault, cf.GenlinenumUsage)
 
-	return generate.Do(&flags, args, func(pkgName string, tm *t.Map, c *check.Checker, files []*a.File) ([]byte, error) {
+	return generate.Do(&flags, args, func(pkgName string, tm *t.Map, files []*a.File) ([]byte, error) {
 		if !cf.IsAlphaNumericIsh(*cformatterFlag) {
 			return nil, fmt.Errorf("bad -cformatter flag value %q", *cformatterFlag)
 		}
@@ -150,7 +149,6 @@
 				pkgPrefix:  "wuffs_" + pkgName + "__",
 				pkgName:    pkgName,
 				tm:         tm,
-				checker:    c,
 				files:      files,
 				genlinenum: *genlinenumFlag,
 			}
@@ -475,9 +473,8 @@
 	pkgPrefix string // e.g. "wuffs_jpeg__"
 	pkgName   string // e.g. "jpeg"
 
-	tm      *t.Map
-	checker *check.Checker
-	files   []*a.File
+	tm    *t.Map
+	files []*a.File
 
 	// genlinenum is whether to print "// foo.wuffs:123" comments in the
 	// generated C code. This can be useful for debugging, although it is not
diff --git a/lang/generate/generate.go b/lang/generate/generate.go
index 5f0f616..6544177 100644
--- a/lang/generate/generate.go
+++ b/lang/generate/generate.go
@@ -30,7 +30,7 @@
 	t "github.com/google/wuffs/lang/token"
 )
 
-type Generator func(packageName string, tm *t.Map, c *check.Checker, files []*a.File) ([]byte, error)
+type Generator func(packageName string, tm *t.Map, files []*a.File) ([]byte, error)
 
 func Do(flags *flag.FlagSet, args []string, g Generator) error {
 	packageName := flags.String("package_name", "", "the package name of the Wuffs input code")
@@ -41,7 +41,7 @@
 
 	if *packageName == "base" && len(flags.Args()) == 0 {
 		var err error
-		out, err = g("base", nil, nil, nil)
+		out, err = g("base", nil, nil)
 		if err != nil {
 			return err
 		}
@@ -58,12 +58,11 @@
 			return err
 		}
 
-		c, err := check.Check(tm, files, resolveUse)
-		if err != nil {
+		if _, err := check.Check(tm, files, resolveUse); err != nil {
 			return err
 		}
 
-		out, err = g(pkgName, tm, c, files)
+		out, err = g(pkgName, tm, files)
 		if err != nil {
 			return err
 		}