Fix Capture into struct value.

See #140, fixes second bug.

bin/go

@@ -1 +1 @@
-.go-1.16.4.pkg
+.go@latest.pkg

bin/gofmt

@@ -1 +1 @@
-.go-1.16.4.pkg
+.go@latest.pkg

grammar.go

@@ -208,7 +208,7 @@ func (g *generatorContext) parseCapture(slexer *structLexer) (node, error) {
 		return &capture{field, n}, nil
 	}
 	ft := indirectType(field.Type)
-	if ft.Kind() == reflect.Struct && ft != tokenType && ft != tokensType && !field.Type.Implements(captureType) && !field.Type.Implements(textUnmarshalerType) {
+	if ft.Kind() == reflect.Struct && ft != tokenType && ft != tokensType && !implements(ft, captureType) && !implements(ft, textUnmarshalerType) {
 		return nil, fmt.Errorf("structs can only be parsed with @@ or by implementing the Capture or encoding.TextUnmarshaler interfaces")
 	}
 	n, err := g.parseTermNoModifiers(slexer, false)
@@ -377,3 +377,7 @@ func indirectType(t reflect.Type) reflect.Type {
 	}
 	return t
 }
+
+func implements(t, i reflect.Type) bool {
+	return t.Implements(i) || reflect.PtrTo(t).Implements(i)
+}

parser_test.go

@@ -1648,3 +1648,35 @@ func BenchmarkIssue143(b *testing.B) {
 		}
 	}
 }
+
+type Boxes struct {
+	Pos   lexer.Position
+	Boxes Box `@Ident`
+}
+
+type Box struct {
+	Pos lexer.Position
+	Val string `@Ident`
+}
+
+func (b *Box) Capture(values []string) error {
+	b.Val = values[0]
+	return nil
+}
+
+func TestBoxedCapture(t *testing.T) {
+	lex := stateful.MustSimple([]stateful.Rule{
+		{"Ident", `[a-zA-Z](\w|\.|/|:|-)*`, nil},
+		{"whitespace", `\s+`, nil},
+	})
+
+	parser := participle.MustBuild(&Boxes{},
+		participle.Lexer(lex),
+		participle.UseLookahead(2),
+	)
+
+	boxed := &Boxes{}
+	if err := parser.ParseString("test", "abc::cdef.abc", boxed); err != nil {
+		t.Fatal(err)
+	}
+}