func maplen(unsafe.Pointer) int

// Len returns v's length.
// It panics if v's Kind is not Array, Chan, Map, Slice, or String.
func (v Value) Len() int {
	k := v.kind()
	switch k {
	case abi.Array:
		tt := (*arrayType)(unsafe.Pointer(v.typ()))
		return int(tt.Len)
	case abi.Chan:
		return chanlen(v.pointer())
	case abi.Map:
		return maplen(v.pointer())
	case abi.Slice:
		// Slice is bigger than a word; assume flagIndir.

	case *ast.BinaryExpr:
		f.walk(&n.X, ctxExpr, visit)
		f.walk(&n.Y, ctxExpr, visit)
	case *ast.KeyValueExpr:
		f.walk(&n.Key, ctxExpr, visit)
		f.walk(&n.Value, ctxExpr, visit)

	case *ast.ArrayType:
		f.walk(&n.Len, ctxExpr, visit)
		f.walk(&n.Elt, ctxType, visit)
	case *ast.StructType:
		f.walk(n.Fields, ctxField, visit)
	case *ast.FuncType:
		if tparams := funcTypeTypeParams(n); tparams != nil {

	case *ast.BinaryExpr:
		a.apply(n, "X", nil, n.X)
		a.apply(n, "Y", nil, n.Y)

	case *ast.KeyValueExpr:
		a.apply(n, "Key", nil, n.Key)
		a.apply(n, "Value", nil, n.Value)

	// Types
	case *ast.ArrayType:
		a.apply(n, "Len", nil, n.Len)
		a.apply(n, "Elt", nil, n.Elt)

	case *ast.StructType:
		a.apply(n, "Fields", nil, n.Fields)

	case *ast.FuncType:
		if tparams := n.TypeParams; tparams != nil {

		walkBeforeAfter(&n.X, before, after)
		walkBeforeAfter(&n.Y, before, after)
	case *ast.KeyValueExpr:
		walkBeforeAfter(&n.Key, before, after)
		walkBeforeAfter(&n.Value, before, after)

	case *ast.ArrayType:
		walkBeforeAfter(&n.Len, before, after)
		walkBeforeAfter(&n.Elt, before, after)
	case *ast.StructType:
		walkBeforeAfter(&n.Fields, before, after)
	case *ast.FuncType:
		if n.TypeParams != nil {

	case Interface:
		return a.assignIntN(offset, goarch.PtrSize, 2, 0b10)
	case Slice:
		return a.assignIntN(offset, goarch.PtrSize, 3, 0b001)
	case Array:
		tt := (*arrayType)(unsafe.Pointer(t))
		switch tt.Len {
		case 0:
			// There's nothing to assign, so don't modify
			// a.steps but succeed so the caller doesn't
			// try to stack-assign this value.
			return true
		case 1:

		case *ast.ValueSpec:
			// rewrite type Typ = [...]Type{...} to type Typ = []Type{...}
			if len(n.Names) == 1 && n.Names[0].Name == "Typ" && len(n.Values) == 1 {
				n.Values[0].(*ast.CompositeLit).Type.(*ast.ArrayType).Len = nil
				return false
			}
		}
		return true
	})
}

// fixSprintf adds an extra nil argument for the *token.FileSet parameter in sprintf calls.
func fixSprintf(f *ast.File) {

	case abi.Int64, abi.Uint64:
		// Only register-assign if the registers are big enough.
		if goarch.PtrSize == 8 {
			return p.assignReg(t.Size_, offset)
		}
	case abi.Array:
		at := (*arraytype)(unsafe.Pointer(t))
		if at.Len == 1 {
			return p.tryRegAssignArg(at.Elem, offset) // TODO fix when runtime is fully commoned up w/ abi.Type
		}
	case abi.Struct:
		st := (*structtype)(unsafe.Pointer(t))

	case *syntax.ParenExpr:
		// Generic types must be instantiated before they can be used in any form.
		// Consequently, generic types cannot be parenthesized.
		return check.definedType(e.X, def)

	case *syntax.ArrayType:
		typ := new(Array)
		setDefType(def, typ)
		if e.Len != nil {
			typ.len = check.arrayLength(e.Len)
		} else {
			// [...]array

	case *ast.ParenExpr:
		// Generic types must be instantiated before they can be used in any form.
		// Consequently, generic types cannot be parenthesized.
		return check.definedType(e.X, def)

	case *ast.ArrayType:
		if e.Len == nil {
			typ := new(Slice)
			setDefType(def, typ)
			typ.elem = check.varType(e.Elt)
			return typ
		}

		typ := new(Array)
		setDefType(def, typ)

			panic("reflect.Value.Bytes of non-byte array")
		}
		if !v.CanAddr() {
			panic("reflect.Value.Bytes of unaddressable byte array")
		}
		p := (*byte)(v.ptr)
		n := int((*arrayType)(unsafe.Pointer(v.typ())).Len)
		return unsafe.Slice(p, n)
	}
	panic(&ValueError{"reflect.Value.Bytes", v.kind()})
}

// runes returns v's underlying value.