2 files changed, 3 insertions, 52 deletions
diff --git a/spec/test/parser.go b/spec/test/parser.go
index e9c557d..aa5d022 100644
--- a/spec/test/parser.go
+++ b/spec/test/parser.go
@@ -99,8 +99,7 @@ func DiffTree(expected, actual *Tree) []*TreeDiff {
 	if expected == nil && actual == nil {
 		return nil
 	}
-	// _ matches any symbols.
-	if expected.Kind != "_" && actual.Kind != expected.Kind {
+	if actual.Kind != expected.Kind {
 		msg := fmt.Sprintf("unexpected kind: expected '%v' but got '%v'", expected.Kind, actual.Kind)
 		return []*TreeDiff{
 			newTreeDiff(expected, actual, msg),
diff --git a/spec/test/parser_test.go b/spec/test/parser_test.go
index cbf96c0..a12c858 100644
--- a/spec/test/parser_test.go
+++ b/spec/test/parser_test.go
@@ -75,26 +75,6 @@ func TestDiffTree(t *testing.T) {
 			),
 		},
 		{
-			t1: NewNonTerminalTree("_"),
-			t2: NewNonTerminalTree("a"),
-		},
-		{
-			t1: NewNonTerminalTree("a",
-				NewNonTerminalTree("_"),
-			),
-			t2: NewNonTerminalTree("a",
-				NewNonTerminalTree("b"),
-			),
-		},
-		{
-			t1: NewNonTerminalTree("_",
-				NewNonTerminalTree("b"),
-			),
-			t2: NewNonTerminalTree("a",
-				NewNonTerminalTree("b"),
-			),
-		},
-		{
 			t1:        NewNonTerminalTree("a"),
 			t2:        NewNonTerminalTree("b"),
 			different: true,
@@ -159,35 +139,6 @@ func TestDiffTree(t *testing.T) {
 			),
 			different: true,
 		},
-		{
-			t1: NewNonTerminalTree("a",
-				NewNonTerminalTree("_"),
-				NewNonTerminalTree("c"),
-			),
-			t2: NewNonTerminalTree("a",
-				NewNonTerminalTree("b"),
-				NewNonTerminalTree("x"),
-			),
-			different: true,
-		},
-		{
-			t1: NewNonTerminalTree("_"),
-			t2: NewNonTerminalTree("a",
-				NewNonTerminalTree("b"),
-			),
-			different: true,
-		},
-		{
-			t1: NewNonTerminalTree("a",
-				NewNonTerminalTree("_"),
-			),
-			t2: NewNonTerminalTree("a",
-				NewNonTerminalTree("b",
-					NewNonTerminalTree("c"),
-				),
-			),
-			different: true,
-		},
 	}
 	for i, tt := range tests {
 		t.Run(fmt.Sprintf("#%v", i), func(t *testing.T) {
@@ -398,12 +349,13 @@ foo x
 `,
 			parseErr: true,
 		},
+		// The error node cannot have another node.
 		{
 			src: `test
 ----
 foo x
 ----
-(foo (error (_ (x 'x'))))
+(foo (error (a)))
 `,
 			parseErr: true,
 		},