Add reflect.Type.ConvertibleTo()

src/internal/reflectlite/type.go

@@ -754,6 +754,98 @@ func (t *RawType) FieldAlign() int {
 	return t.Align()
 }
 
+// ConvertibleTo returns whether a value of type t can be converted to a variable of type u
+func (r *RawType) ConvertibleTo(u *RawType) bool {
+
+	// This logic is mostly copied from Value.CanConvert
+
+	switch r.Kind() {
+	case Int, Int8, Int16, Int32, Int64:
+		switch u.Kind() {
+		case Int, Int8, Int16, Int32, Int64, Uint, Uint8, Uint16, Uint32, Uint64, Uintptr:
+			return true
+		case Float32, Float64:
+			return true
+		case String:
+			return true
+		}
+
+	case Uint, Uint8, Uint16, Uint32, Uint64, Uintptr:
+		switch u.Kind() {
+		case Int, Int8, Int16, Int32, Int64, Uint, Uint8, Uint16, Uint32, Uint64, Uintptr:
+			return true
+		case Float32, Float64:
+			return true
+		case String:
+			return true
+		}
+
+	case Float32, Float64:
+		switch u.Kind() {
+		case Int, Int8, Int16, Int32, Int64:
+			return true
+		case Uint, Uint8, Uint16, Uint32, Uint64, Uintptr:
+			return true
+		case Float32, Float64:
+			return true
+		}
+
+	case Complex64, Complex128:
+		switch u.Kind() {
+		case Complex64, Complex128:
+			return true
+		}
+
+	case Slice:
+		switch u.Kind() {
+		case Array:
+			// This may fail at runtime if there isn't room
+			if r.elem() == u.elem() {
+				return true
+			}
+
+		case Pointer:
+			// This may fail at runtime if there isn't room
+			if u.elem().Kind() == Array && r.elem() == u.elem().elem() {
+				return true
+			}
+
+		case String:
+			// bytes or runes
+			if !r.elem().isNamed() && (r.elem().Kind() == Uint8 || r.elem().Kind() == Int32) {
+				return true
+			}
+
+		}
+
+	case String:
+		// bytes or runes
+		if u.Kind() == Slice && !u.elem().isNamed() && (u.elem().Kind() == Uint8 || u.elem().Kind() == Int32) {
+			return true
+		}
+
+	case Pointer:
+		if !r.isNamed() && u.Kind() == Pointer && !u.isNamed() && r.elem().underlying() == u.elem().underlying() {
+			return true
+		}
+	}
+
+	if r.underlying() == u.underlying() {
+		return true
+	}
+
+	if u.Kind() == Interface && u.NumMethod() == 0 {
+		return true
+	}
+
+	// TODO(dgryski): Unimplemented
+	// struct types
+	// channels
+
+	return false
+
+}
+
 // AssignableTo returns whether a value of type t can be assigned to a variable
 // of type u.
 func (t *RawType) AssignableTo(u Type) bool {

src/internal/reflectlite/value.go

@@ -51,6 +51,22 @@ func (v Value) isRO() bool {
 	return v.flags&(valueFlagRO) != 0
 }
 
+// These are package methods, not methods on Value, since the reflect.Value embeds a reflectlite.Value, so any
+// methods added to reflectlite.Value are visible to the user.
+
+func IsRO(v Value) bool {
+	return v.isRO()
+}
+
+func MakeRO(v Value, ro bool) Value {
+	if ro {
+		v.flags |= valueFlagRO
+	} else {
+		v.flags &^= valueFlagRO
+	}
+	return v
+}
+
 func (v Value) checkRO() {
 	if v.isRO() {
 		panic("reflect: value is not settable")
@@ -1485,13 +1501,11 @@ func convertOp(src Value, typ Type) (Value, bool) {
 			return cvtFloat(src, rtype), true
 		}
 
-		/*
-			case Complex64, Complex128:
-				switch src.Kind() {
-				case Complex64, Complex128:
-					return cvtComplex
-				}
-		*/
+	case Complex64, Complex128:
+		switch rtype := typ.(*RawType); rtype.Kind() {
+		case Complex64, Complex128:
+			return cvtComplex(src, rtype), true
+		}
 
 	case Slice:
 		switch rtype := typ.(*RawType); rtype.Kind() {
@@ -1534,6 +1548,12 @@ func convertOp(src Value, typ Type) (Value, bool) {
 				return cvtStringRunes(src, rtype), true
 			}
 		}
+
+	case Pointer:
+		rtype := typ.(*RawType)
+		if rtype.Kind() == Pointer && !src.typecode.isNamed() && !rtype.isNamed() && src.typecode.elem().underlying() == rtype.elem().underlying() {
+			return cvtDirect(src, rtype), true
+		}
 	}
 
 	// TODO(dgryski): Unimplemented:
@@ -1578,6 +1598,18 @@ func cvtFloat(v Value, t *RawType) Value {
 	return makeFloat(v.flags, v.Float(), t)
 }
 
+func cvtDirect(v Value, t *RawType) Value {
+	return Value{
+		typecode: t,
+		value:    v.value,
+		flags:    v.flags,
+	}
+}
+
+func cvtComplex(v Value, t *RawType) Value {
+	return makeComplex(v.flags, v.Complex(), t)
+}
+
 //go:linkname stringToBytes runtime.stringToBytes
 func stringToBytes(x string) []byte
 
@@ -1661,20 +1693,76 @@ func makeFloat32(flags valueFlags, f float32, t *RawType) Value {
 	return v
 }
 
-func cvtIntString(src Value, t *RawType) Value {
-	panic("cvtUintString: unimplemented")
+func makeComplex(flags valueFlags, f complex128, t *RawType) Value {
+	size := t.Size()
+
+	v := Value{
+		typecode: t,
+		flags:    flags,
+	}
+
+	ptr := unsafe.Pointer(&v.value)
+	if size > unsafe.Sizeof(uintptr(0)) {
+		ptr = alloc(size, nil)
+		v.value = ptr
+	}
+
+	switch size {
+	case 8:
+		*(*complex64)(ptr) = complex64(f)
+	case 16:
+		*(*complex128)(ptr) = f
+	}
+	return v
+}
+
+func cvtIntString(v Value, t *RawType) Value {
+	s := "\uFFFD"
+	if x := v.Int(); int64(rune(x)) == x {
+		s = string(rune(x))
+	}
+	return Value{
+		typecode: t,
+		value:    unsafe.Pointer(&s),
+		flags:    v.flags,
+	}
 }
 
-func cvtUintString(src Value, t *RawType) Value {
-	panic("cvtUintString: unimplemented")
+func cvtUintString(v Value, t *RawType) Value {
+	s := "\uFFFD"
+	if x := v.Uint(); uint64(rune(x)) == x {
+		s = string(rune(x))
+	}
+
+	return Value{
+		typecode: t,
+		value:    unsafe.Pointer(&s),
+		flags:    v.flags,
+	}
 }
 
-func cvtStringRunes(src Value, t *RawType) Value {
-	panic("cvsStringRunes: unimplemented")
+//go:linkname stringToRunes runtime.stringToRunes
+func stringToRunes(s string) []rune
+
+func cvtStringRunes(v Value, t *RawType) Value {
+	b := stringToRunes(*(*string)(v.value))
+	return Value{
+		typecode: t,
+		value:    unsafe.Pointer(&b),
+		flags:    v.flags,
+	}
 }
 
-func cvtRunesString(src Value, t *RawType) Value {
-	panic("cvsRunesString: unimplemented")
+//go:linkname stringFromRunes runtime.stringFromRunes
+func stringFromRunes(r []rune) string
+
+func cvtRunesString(v Value, t *RawType) Value {
+	s := stringFromRunes(*(*[]rune)(v.value))
+	return Value{
+		typecode: t,
+		value:    unsafe.Pointer(&s),
+		flags:    v.flags,
+	}
 }
 
 //go:linkname slicePanic runtime.slicePanic