From 8115ae198d192f778a3586596c8550665f409823 Mon Sep 17 00:00:00 2001 From: Rob Findley Date: Thu, 10 Jun 2021 12:23:40 -0400 Subject: [PATCH] [dev.typeparams] go/types: disallow ~T where T is a defined type or an interface This is a straightforward port of CL 324570 to go/types. Change-Id: I1395775a1d21a903a57e0cefc4e240cfa2bb8e97 Reviewed-on: https://go-review.googlesource.com/c/go/+/326684 Trust: Robert Findley Run-TryBot: Robert Findley TryBot-Result: Go Bot Reviewed-by: Robert Griesemer --- src/go/types/testdata/check/typeinst2.go2 | 4 ++-- src/go/types/testdata/examples/constraints.go2 | 9 +++++++++ src/go/types/testdata/fixedbugs/issue39634.go2 | 4 ++-- src/go/types/union.go | 11 ++++++----- 4 files changed, 19 insertions(+), 9 deletions(-) diff --git a/src/go/types/testdata/check/typeinst2.go2 b/src/go/types/testdata/check/typeinst2.go2 index a4c9f58c09..ab56ccafc9 100644 --- a/src/go/types/testdata/check/typeinst2.go2 +++ b/src/go/types/testdata/check/typeinst2.go2 @@ -176,12 +176,12 @@ type _ interface { // Interface type lists can contain any type, incl. *Named types. // Verify that we use the underlying type to compute the operational type. type MyInt int -func add1[T interface{~MyInt}](x T) T { +func add1[T interface{MyInt}](x T) T { return x + 1 } type MyString string -func double[T interface{~MyInt | ~MyString}](x T) T { +func double[T interface{MyInt|MyString}](x T) T { return x + x } diff --git a/src/go/types/testdata/examples/constraints.go2 b/src/go/types/testdata/examples/constraints.go2 index 61992e4c2a..d9805fe694 100644 --- a/src/go/types/testdata/examples/constraints.go2 +++ b/src/go/types/testdata/examples/constraints.go2 @@ -36,6 +36,15 @@ type ( _ interface{int|interface /* ERROR cannot use interface */ {}} ) +type ( + // Tilde is not permitted on defined types or interfaces. + foo int + bar interface{} + _ interface{foo} + _ interface{~ /* ERROR invalid use of ~ */ foo } + _ interface{~ /* ERROR invalid use of ~ */ bar } +) + // Multiple embedded union elements are intersected. The order in which they // appear in the interface doesn't matter since intersection is a symmetric // operation. diff --git a/src/go/types/testdata/fixedbugs/issue39634.go2 b/src/go/types/testdata/fixedbugs/issue39634.go2 index 8decff5291..2a1367373f 100644 --- a/src/go/types/testdata/fixedbugs/issue39634.go2 +++ b/src/go/types/testdata/fixedbugs/issue39634.go2 @@ -36,8 +36,8 @@ func bar8[A foo8[A]](a A) {} func main8() {} // crash 9 -type foo9[A any] interface { ~ /* ERROR cannot use interface */ foo9 [A] } -func _() { var _ = new(foo9 /* ERROR interface contains type constraints */ [int]) } +type foo9[A any] interface { foo9 /* ERROR illegal cycle */ [A] } +func _() { var _ = new(foo9 /* ERROR illegal cycle */ [int]) } // crash 12 var u /* ERROR cycle */ , i [func /* ERROR used as value */ /* ERROR used as value */ (u, c /* ERROR undeclared */ /* ERROR undeclared */ ) {}(0, len /* ERROR must be called */ /* ERROR must be called */ )]c /* ERROR undeclared */ /* ERROR undeclared */ diff --git a/src/go/types/union.go b/src/go/types/union.go index 4eda874eb8..690b734d76 100644 --- a/src/go/types/union.go +++ b/src/go/types/union.go @@ -109,17 +109,18 @@ func parseUnion(check *Checker, tlist []ast.Expr) Type { } u := under(t) - if tilde[i] { - // TODO(rfindley) enable this check once we have converted tests - // if !Identical(u, t) { - // check.errorf(x, "invalid use of ~ (underlying type of %s is %s)", t, u) - // } + if tilde[i] && !Identical(u, t) { + check.errorf(x, _Todo, "invalid use of ~ (underlying type of %s is %s)", t, u) + continue // don't report another error for t } if _, ok := u.(*Interface); ok { + // A single type with a ~ is a single-term union. check.errorf(atPos(pos), _Todo, "cannot use interface %s with ~ or inside a union (implementation restriction)", t) + continue // don't report another error for t } // Complain about duplicate entries a|a, but also a|~a, and ~a|~a. + // TODO(gri) We should also exclude myint|~int since myint is included in ~int. if includes(types[:i], t) { // TODO(rfindley) this currently doesn't print the ~ if present check.softErrorf(atPos(pos), _Todo, "duplicate term %s in union element", t)