perf(decode): parse struct destinations without the value tree

Assisted-by: GLM 5.3 Flash

bench_test.go

@@ -4,6 +4,7 @@
 package interpres
 
 import (
+	"context"
 	"fmt"
 	"strings"
 	"testing"
@@ -168,3 +169,39 @@ func BenchmarkMarshalLong(b *testing.B) {
 		}
 	}
 }
+
+// BenchmarkStrictDecodeTree measures the reference path the targeted decode
+// is measured against: the full tree parse followed by the reflection walk.
+// The pair runs in one process, so the A/B comparison shares the machine.
+func BenchmarkStrictDecodeTree(b *testing.B) {
+	dec := newDecoder()
+	dec.disallowUnknown = true
+	b.ReportAllocs()
+	for b.Loop() {
+		tree, _, err := parseWithOptions(context.Background(), benchDoc, parseOptions{}, false)
+		if err != nil {
+			b.Fatal(err)
+		}
+		var cfg benchConfig
+		if err := dec.decode(tree, &cfg); err != nil {
+			b.Fatal(err)
+		}
+	}
+}
+
+func BenchmarkStrictDecodeTreeLong(b *testing.B) {
+	dec := newDecoder()
+	dec.disallowUnknown = true
+	b.ReportAllocs()
+	b.SetBytes(int64(len(longDoc)))
+	for b.Loop() {
+		tree, _, err := parseWithOptions(context.Background(), longDoc, parseOptions{}, false)
+		if err != nil {
+			b.Fatal(err)
+		}
+		var doc benchLongDoc
+		if err := dec.decode(tree, &doc); err != nil {
+			b.Fatal(err)
+		}
+	}
+}