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// Copyright 2022 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Field accesses through type parameters are disabled
// until we have a more thorough understanding of the
// implications on the spec. See issue #51576.
package p
// The first example from the issue.
type Numeric interface {
~int | ~int8 | ~int16 | ~int32 | ~int64
}
// numericAbs matches numeric types with an Abs method.
type numericAbs[T Numeric] interface {
~struct{ Value T }
Abs() T
}
// AbsDifference computes the absolute value of the difference of
// a and b, where the absolute value is determined by the Abs method.
func absDifference[T numericAbs[T /* ERROR "T does not satisfy Numeric" */]](a, b T) T {
// Field accesses are not permitted for now. Keep an error so
// we can find and fix this code once the situation changes.
return a.Value // ERROR "a.Value undefined"
// TODO: The error below should probably be positioned on the '-'.
// d := a /* ERROR "invalid operation: operator - not defined" */ .Value - b.Value
// return d.Abs()
}
// The second example from the issue.
type T[P int] struct{ f P }
func _[P T[P /* ERROR "P does not satisfy int" */ ]]() {}
// Additional tests
func _[P T[T /* ERROR "T[P] does not satisfy int" */ [P /* ERROR "P does not satisfy int" */ ]]]() {}
func _[P T[Q /* ERROR "Q does not satisfy int" */ ], Q T[P /* ERROR "P does not satisfy int" */ ]]() {}
func _[P T[Q], Q int]() {}
type C[P comparable] struct{ f P }
func _[P C[C[P]]]() {}
func _[P C[C /* ERROR "C[Q] does not satisfy comparable" */ [Q /* ERROR "Q does not satisfy comparable" */]], Q func()]() {}
func _[P [10]C[P]]() {}
func _[P struct{ f C[C[P]]}]() {}