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[go1.20] Removing remaining uses of unsafeheader.Slice from reflect #1322

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Merged
merged 1 commit into from
Jul 16, 2024
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[go1.20] Removing remaining uses of unsafeheader.Slice from reflect #1322

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16 changes: 16 additions & 0 deletions compiler/natives/src/internal/unsafeheader/unsafeheader.go
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Original file line number Diff line number Diff line change
@@ -0,0 +1,16 @@
//go:build js
// +build js

package unsafeheader

// Slice and String is Go's runtime representations which is different
// from GopherJS's runtime representations. By purging these types,
// it will prevent failures in JS where the code compiles fine but
// expects there to be a constructor which doesn't exist when casting
// from GopherJS's representation into Go's representation.

//gopherjs:purge
type Slice struct{}

//gopherjs:purge
type String struct{}
10 changes: 10 additions & 0 deletions compiler/natives/src/internal/unsafeheader/unsafeheader_test.go
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Expand Up @@ -5,6 +5,16 @@ package unsafeheader_test

import "testing"

func TestTypeMatchesReflectType(t *testing.T) {
t.Skip("GopherJS uses different slice and string implementation than internal/unsafeheader.")
}

//gopherjs:purge
func testHeaderMatchesReflect()

//gopherjs:purge
func typeCompatible()

func TestWriteThroughHeader(t *testing.T) {
t.Skip("GopherJS uses different slice and string implementation than internal/unsafeheader.")
}
15 changes: 15 additions & 0 deletions compiler/natives/src/reflect/reflect.go
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Expand Up @@ -832,6 +832,21 @@ func cvtSliceArrayPtr(v Value, t Type) Value {
return Value{t.common(), unsafe.Pointer(array.Unsafe()), v.flag&^(flagIndir|flagAddr|flagKindMask) | flag(Ptr)}
}

// convertOp: []T -> [N]T
func cvtSliceArray(v Value, t Type) Value {
n := t.Len()
if n > v.Len() {
panic("reflect: cannot convert slice with length " + itoa.Itoa(v.Len()) + " to array with length " + itoa.Itoa(n))
}

slice := v.object()
dst := MakeSlice(SliceOf(t.Elem()), n, n).object()
js.Global.Call("$copySlice", dst, slice)

arr := dst.Get("$array")
return Value{t.common(), unsafe.Pointer(arr.Unsafe()), v.flag&^(flagAddr|flagKindMask) | flag(Array)}
}

func Copy(dst, src Value) int {
dk := dst.kind()
if dk != Array && dk != Slice {
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2 changes: 1 addition & 1 deletion compiler/prelude/prelude.js
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Expand Up @@ -185,7 +185,7 @@ var $sliceToNativeArray = slice => {
return slice.$array.slice(slice.$offset, slice.$offset + slice.$length);
};

// Convert Go slice to a pointer to an underlying Go array.
// Convert Go slice to a pointer to an underlying Go array, `[]T -> *[N]T`.
//
// Note that an array pointer can be represented by an "unwrapped" native array
// type, and it will be wrapped back into its Go type when necessary.
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