enable errcheck for the project and fix the violations discovered

.golangci.yml

@@ -9,6 +9,7 @@ linters:
   disable-all: true
   enable:
   - bodyclose
+  - errcheck
   - errname
   - gofmt
   - goimports

corpus_test.go

@@ -197,7 +197,7 @@ func TestCorpus(t *testing.T) {
 					action := cedar.EntityUID(request.Action)
 					resource := cedar.EntityUID(request.Resource)
 					context := request.Context
-					batch.Authorize(ctx, policySet, entities, batch.Request{
+					err := batch.Authorize(ctx, policySet, entities, batch.Request{
 						Principal: batch.Variable("principal"),
 						Action:    batch.Variable("action"),
 						Resource:  batch.Variable("resource"),
@@ -212,6 +212,7 @@ func TestCorpus(t *testing.T) {
 						res = r
 						total++
 					})
+					testutil.OK(t, err)
 					testutil.Equals(t, total, 1)
 					testutil.Equals(t, res.Request.Principal, principal)
 					testutil.Equals(t, res.Request.Action, action)

internal/eval/partial_test.go

@@ -1212,7 +1212,7 @@ func TestPartialBasic(t *testing.T) {
 func TestPartialPanic(t *testing.T) {
 	t.Parallel()
 	testutil.Panic(t, func() {
-		partial(Env{}, nil)
+		_, _ = partial(Env{}, nil)
 	})
 }
 

internal/json/json_marshal.go

@@ -47,19 +47,16 @@ func (s *scopeJSON) FromNode(src ast.IsScopeNode) {
 	}
 }
 
-func unaryToJSON(dest **unaryJSON, src ast.UnaryNode) error {
-	n := ast.UnaryNode(src)
+func unaryToJSON(dest **unaryJSON, src ast.UnaryNode) {
 	res := &unaryJSON{}
-	res.Arg.FromNode(n.Arg)
+	res.Arg.FromNode(src.Arg)
 	*dest = res
-	return nil
 }
 
 func binaryToJSON(dest **binaryJSON, src ast.BinaryNode) {
-	n := ast.BinaryNode(src)
 	res := &binaryJSON{}
-	res.Left.FromNode(n.Left)
-	res.Right.FromNode(n.Right)
+	res.Left.FromNode(src.Left)
+	res.Right.FromNode(src.Right)
 	*dest = res
 }