encoding/gob: make use of reflect.TypeAssert

Use "reflect.TypeAssert" to simplify the code.

There are also some performance gains:

goarch: arm64
pkg: encoding/gob
cpu: Apple M4
                         │     old     │                 new                 │
                         │   sec/op    │   sec/op     vs base                │
EncodeComplex128Slice-10   1.048µ ± 3%   1.048µ ± 1%        ~ (p=0.986 n=10)
EncodeFloat64Slice-10      481.5n ± 0%   538.1n ± 0%  +11.75% (p=0.000 n=10)
EncodeInt32Slice-10        560.0n ± 1%   562.2n ± 1%        ~ (p=0.239 n=10)
EncodeStringSlice-10       713.1n ± 2%   690.1n ± 1%   -3.24% (p=0.000 n=10)
EncodeInterfaceSlice-10    16.10µ ± 3%   16.89µ ± 3%   +4.94% (p=0.004 n=10)
DecodeComplex128Slice-10   5.507µ ± 2%   5.488µ ± 2%        ~ (p=0.617 n=10)
DecodeFloat64Slice-10      3.359µ ± 1%   3.365µ ± 1%        ~ (p=0.403 n=10)
DecodeInt32Slice-10        3.296µ ± 1%   3.290µ ± 2%        ~ (p=0.926 n=10)
DecodeStringSlice-10       8.397µ ± 2%   8.459µ ± 1%        ~ (p=0.796 n=10)
DecodeStringsSlice-10      18.47µ ± 1%   11.14µ ± 1%  -39.69% (p=0.000 n=10)
DecodeBytesSlice-10        5.038µ ± 1%   5.039µ ± 1%        ~ (p=0.956 n=10)
DecodeInterfaceSlice-10    40.14µ ± 1%   40.60µ ± 1%   +1.16% (p=0.001 n=10)
DecodeMap-10               43.43µ ± 1%   44.09µ ± 1%   +1.51% (p=0.000 n=10)
geomean                    4.451µ        4.335µ        -2.62%

                         │      old       │                  new                   │
                         │      B/op      │     B/op      vs base                  │
EncodeComplex128Slice-10    1.0000 ±  ?      0.5000 ±  ?        ~ (p=0.350 n=10)
EncodeFloat64Slice-10        0.000 ± 0%       0.000 ± 0%        ~ (p=1.000 n=10) ¹
EncodeInt32Slice-10          0.000 ± 0%       0.000 ± 0%        ~ (p=1.000 n=10) ¹
EncodeStringSlice-10         0.000 ± 0%       0.000 ± 0%        ~ (p=1.000 n=10) ¹
EncodeInterfaceSlice-10      19.00 ± 5%       20.00 ± 5%   +5.26% (p=0.002 n=10)
DecodeComplex128Slice-10   24.55Ki ± 0%     24.53Ki ± 0%   -0.10% (p=0.000 n=10)
DecodeFloat64Slice-10      10.56Ki ± 0%     10.54Ki ± 0%   -0.22% (p=0.000 n=10)
DecodeInt32Slice-10        9.539Ki ± 0%     9.516Ki ± 0%   -0.25% (p=0.000 n=10)
DecodeStringSlice-10       38.18Ki ± 0%     38.16Ki ± 0%   -0.06% (p=0.000 n=10)
DecodeStringsSlice-10      63.96Ki ± 0%     40.51Ki ± 0%  -36.65% (p=0.000 n=10)
DecodeBytesSlice-10        22.58Ki ± 0%     22.58Ki ± 0%        ~ (p=1.000 n=10)
DecodeInterfaceSlice-10    80.47Ki ± 0%     80.47Ki ± 0%        ~ (p=1.000 n=10)
DecodeMap-10               48.81Ki ± 0%     48.81Ki ± 0%        ~ (p=1.000 n=10) ¹
geomean                                 ²                  -8.15%                ²
¹ all samples are equal
² summaries must be >0 to compute geomean

                         │      old      │                  new                  │
                         │   allocs/op   │  allocs/op   vs base                  │
EncodeComplex128Slice-10    0.000 ± 0%      0.000 ± 0%        ~ (p=1.000 n=10) ¹
EncodeFloat64Slice-10       0.000 ± 0%      0.000 ± 0%        ~ (p=1.000 n=10) ¹
EncodeInt32Slice-10         0.000 ± 0%      0.000 ± 0%        ~ (p=1.000 n=10) ¹
EncodeStringSlice-10        0.000 ± 0%      0.000 ± 0%        ~ (p=1.000 n=10) ¹
EncodeInterfaceSlice-10     0.000 ± 0%      0.000 ± 0%        ~ (p=1.000 n=10) ¹
DecodeComplex128Slice-10    149.0 ± 0%      148.0 ± 0%   -0.67% (p=0.000 n=10)
DecodeFloat64Slice-10       150.0 ± 0%      149.0 ± 0%   -0.67% (p=0.000 n=10)
DecodeInt32Slice-10         149.0 ± 0%      148.0 ± 0%   -0.67% (p=0.000 n=10)
DecodeStringSlice-10       1.150k ± 0%     1.149k ± 0%   -0.09% (p=0.000 n=10)
DecodeStringsSlice-10      2.158k ± 0%     1.158k ± 0%  -46.34% (p=0.000 n=10)
DecodeBytesSlice-10         149.0 ± 0%      149.0 ± 0%        ~ (p=1.000 n=10) ¹
DecodeInterfaceSlice-10    3.158k ± 0%     3.158k ± 0%        ~ (p=1.000 n=10) ¹
DecodeMap-10                160.0 ± 0%      160.0 ± 0%        ~ (p=1.000 n=10) ¹
geomean                                ²                 -4.83%                ²
¹ all samples are equal
² summaries must be >0 to compute geomean

Updates golang#62121

Change-Id: I1d3534e5001ca185bc8ba5a7ed4ddbc00f85a17e
GitHub-Last-Rev: c0209f8
GitHub-Pull-Request: golang#75409
Reviewed-on: https://go-review.googlesource.com/c/go/+/702735
Reviewed-by: Mark Freeman <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Auto-Submit: Michael Pratt <[email protected]>
Reviewed-by: Daniel Martí <[email protected]>
Reviewed-by: Michael Pratt <[email protected]>

Author: apocelipes

src/encoding/gob/dec_helpers.go

@@ -231,7 +231,7 @@ func dec%[2]sArray(state *decoderState, v reflect.Value, length int, ovfl error)
 
 const sliceHelper = `
 func dec%[2]sSlice(state *decoderState, v reflect.Value, length int, ovfl error) bool {
-	slice, ok := v.Interface().([]%[1]s)
+	slice, ok := reflect.TypeAssert[[]%[1]s](v)
 	if !ok {
 		// It is kind %[1]s but not type %[1]s. TODO: We can handle this unsafely.
 		return false

src/encoding/gob/decgen.go

@@ -768,11 +768,14 @@ func (dec *Decoder) decodeGobDecoder(ut *userTypeInfo, state *decoderState, valu
 	// We know it's one of these.
 	switch ut.externalDec {
 	case xGob:
-		err = value.Interface().(GobDecoder).GobDecode(b)
+		gobDecoder, _ := reflect.TypeAssert[GobDecoder](value)
+		err = gobDecoder.GobDecode(b)
 	case xBinary:
-		err = value.Interface().(encoding.BinaryUnmarshaler).UnmarshalBinary(b)
+		binaryUnmarshaler, _ := reflect.TypeAssert[encoding.BinaryUnmarshaler](value)
+		err = binaryUnmarshaler.UnmarshalBinary(b)
 	case xText:
-		err = value.Interface().(encoding.TextUnmarshaler).UnmarshalText(b)
+		textUnmarshaler, _ := reflect.TypeAssert[encoding.TextUnmarshaler](value)
+		err = textUnmarshaler.UnmarshalText(b)
 	}
 	if err != nil {
 		error_(err)

src/encoding/gob/decode.go

@@ -208,7 +208,7 @@ func enc%[2]sArray(state *encoderState, v reflect.Value) bool {
 
 const sliceHelper = `
 func enc%[2]sSlice(state *encoderState, v reflect.Value) bool {
-	slice, ok := v.Interface().([]%[1]s)
+	slice, ok := reflect.TypeAssert[[]%[1]s](v)
 	if !ok {
 		// It is kind %[1]s but not type %[1]s. TODO: We can handle this unsafely.
 		return false

src/encoding/gob/enc_helpers.go

@@ -440,11 +440,14 @@ func (enc *Encoder) encodeGobEncoder(b *encBuffer, ut *userTypeInfo, v reflect.V
 	// We know it's one of these.
 	switch ut.externalEnc {
 	case xGob:
-		data, err = v.Interface().(GobEncoder).GobEncode()
+		gobEncoder, _ := reflect.TypeAssert[GobEncoder](v)
+		data, err = gobEncoder.GobEncode()
 	case xBinary:
-		data, err = v.Interface().(encoding.BinaryMarshaler).MarshalBinary()
+		binaryMarshaler, _ := reflect.TypeAssert[encoding.BinaryMarshaler](v)
+		data, err = binaryMarshaler.MarshalBinary()
 	case xText:
-		data, err = v.Interface().(encoding.TextMarshaler).MarshalText()
+		textMarshaler, _ := reflect.TypeAssert[encoding.TextMarshaler](v)
+		data, err = textMarshaler.MarshalText()
 	}
 	if err != nil {
 		error_(err)