go/types, types2: remove support for gotypesalias GODEBUG flag

For #76472.

Change-Id: Ia51b41639637b1de916625e73c26f625382be305
Reviewed-on: https://go-review.googlesource.com/c/go/+/736441
Reviewed-by: Alan Donovan <adonovan@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Robert Griesemer <gri@google.com>
Reviewed-by: Robert Griesemer <gri@google.com>
Commit-Queue: Robert Griesemer <gri@google.com>

20 files changed, 5 insertions, 292 deletions

diff --git a/src/internal/godebugs/table.go b/src/internal/godebugs/table.go
index 87b499385a..a7c984b5e2 100644
--- a/src/internal/godebugs/table.go
+++ b/src/internal/godebugs/table.go
@@ -39,7 +39,6 @@ var All = []Info{
 	{Name: "gocachetest", Package: "cmd/go"},
 	{Name: "gocacheverify", Package: "cmd/go"},
 	{Name: "gotestjsonbuildtext", Package: "cmd/go", Changed: 24, Old: "1"},
-	{Name: "gotypesalias", Package: "go/types", Changed: 23, Old: "0"},
 	{Name: "http2client", Package: "net/http"},
 	{Name: "http2debug", Package: "net/http", Opaque: true},
 	{Name: "http2server", Package: "net/http"},
@@ -90,6 +89,7 @@ type RemovedInfo struct {
 // Removed contains all GODEBUGs that we have removed.
 var Removed = []RemovedInfo{
 	{Name: "x509sha1", Removed: 24},
+	{Name: "gotypesalias", Removed: 27},
 }
 
 // Lookup returns the Info with the given name.
diff --git a/src/internal/types/testdata/check/cycles5.go b/src/internal/types/testdata/check/cycles5.go
index 9605f8ded4..40a6d9b483 100644
--- a/src/internal/types/testdata/check/cycles5.go
+++ b/src/internal/types/testdata/check/cycles5.go
@@ -1,5 +1,3 @@
-// -gotypesalias=0
-
 // Copyright 2017 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.
@@ -137,7 +135,7 @@ type (
 type (
 	a struct{ *b }
 	b = c
-	c struct{ *b /* ERROR "invalid use of type alias" */ }
+	c struct{ *b }
 )
 
 // issue #24939
@@ -147,7 +145,7 @@ type (
 	}
 
 	M interface {
-		F() P // ERROR "invalid use of type alias"
+		F() P
 	}
 
 	P = interface {
diff --git a/src/internal/types/testdata/check/cycles5a.go b/src/internal/types/testdata/check/cycles5a.go
deleted file mode 100644
index a8cad50243..0000000000
--- a/src/internal/types/testdata/check/cycles5a.go
+++ /dev/null
@@ -1,202 +0,0 @@
-// -gotypesalias=1
-
-// Copyright 2017 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.
-
-package p
-
-import "unsafe"
-
-// test case from issue #18395
-
-type (
-	A interface { B }
-	B interface { C }
-	C interface { D; F() A }
-	D interface { G() B }
-)
-
-var _ = A(nil).G // G must be found
-
-
-// test case from issue #21804
-
-type sourceBridge interface {
-	listVersions() ([]Version, error)
-}
-
-type Constraint interface {
-	copyTo(*ConstraintMsg)
-}
-
-type ConstraintMsg struct{}
-
-func (m *ConstraintMsg) asUnpairedVersion() UnpairedVersion {
-	return nil
-}
-
-type Version interface {
-	Constraint
-}
-
-type UnpairedVersion interface {
-	Version
-}
-
-var _ Constraint = UnpairedVersion(nil)
-
-
-// derived test case from issue #21804
-
-type (
-	_ interface{ m(B1) }
-	A1 interface{ a(D1) }
-	B1 interface{ A1 }
-	C1 interface{ B1 }
-	D1 interface{ C1 }
-)
-
-var _ A1 = C1(nil)
-
-
-// derived test case from issue #22701
-
-func F(x I4) interface{} {
-	return x.Method()
-}
-
-type Unused interface {
-	RefersToI1(a I1)
-}
-
-type I1 interface {
-	I2
-	I3
-}
-
-type I2 interface {
-	RefersToI4() I4
-}
-
-type I3 interface {
-	Method() interface{}
-}
-
-type I4 interface {
-	I1
-}
-
-
-// check embedding of error interface
-
-type Error interface{ error }
-
-var err Error
-var _ = err.Error()
-
-
-// more esoteric cases
-
-type (
-	T1 interface { T2 }
-	T2 /* ERROR "invalid recursive type" */ T2
-)
-
-type (
-	T3 interface { T4 }
-	T4 /* ERROR "invalid recursive type" */ T5
-	T5 = T6
-	T6 = T7
-	T7 = T4
-)
-
-
-// arbitrary code may appear inside an interface
-
-const n = unsafe.Sizeof(func(){})
-
-type I interface {
-	m([unsafe.Sizeof(func() { I.m(nil, [n]byte{}) })]byte)
-}
-
-
-// test cases for varias alias cycles
-
-type T10 /* ERROR "invalid recursive type" */ = *T10                 // issue #25141
-type T11 /* ERROR "invalid recursive type" */ = interface{ f(T11) }  // issue #23139
-
-// issue #18640
-type (
-	aa = bb
-	bb struct {
-		*aa
-	}
-)
-
-type (
-	a struct{ *b }
-	b = c
-	c struct{ *b }
-)
-
-// issue #24939
-type (
-	_ interface {
-		M(P)
-	}
-
-	M interface {
-		F() P
-	}
-
-	P = interface {
-		I() M
-	}
-)
-
-// issue #8699
-type T12 /* ERROR "invalid recursive type" */ [len(a12)]int
-var a12 = makeArray()
-func makeArray() (res T12) { return }
-
-// issue #20770
-var r = newReader()
-func newReader() r // ERROR "r (package-level variable) is not a type"
-
-// variations of the theme of #8699 and #20770
-var arr /* ERROR "cycle" */ = f()
-func f() [len(arr)]int
-
-// issue #25790
-func ff(ff /* ERROR "not a type" */ )
-func gg((gg /* ERROR "not a type" */ ))
-
-type T13 /* ERROR "invalid recursive type T13" */ [len(b13)]int
-var b13 T13
-
-func g1() [unsafe.Sizeof(g1)]int
-func g2() [unsafe.Sizeof(x2)]int
-var x2 = g2
-
-// verify that we get the correct sizes for the functions above
-// (note: assert is statically evaluated in go/types test mode)
-func init() {
-	assert(unsafe.Sizeof(g1) == 8)
-	assert(unsafe.Sizeof(x2) == 8)
-}
-
-func h() [h /* ERROR "no value" */ ()[0]]int { panic(0) }
-
-var c14 /* ERROR "cycle" */ T14
-type T14 [uintptr(unsafe.Sizeof(&c14))]byte
-
-// issue #34333
-type T15 /* ERROR "invalid recursive type T15" */ struct {
-	f func() T16
-	b T16
-}
-
-type T16 struct {
-	T15
-}
\ No newline at end of file
diff --git a/src/internal/types/testdata/fixedbugs/issue46461.go b/src/internal/types/testdata/fixedbugs/issue46461.go
index 454f7e8365..8bf31090b8 100644
--- a/src/internal/types/testdata/fixedbugs/issue46461.go
+++ b/src/internal/types/testdata/fixedbugs/issue46461.go
@@ -1,5 +1,3 @@
-// -gotypesalias=0
-
 // Copyright 2021 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.
diff --git a/src/internal/types/testdata/fixedbugs/issue46461a.go b/src/internal/types/testdata/fixedbugs/issue46461a.go
deleted file mode 100644
index 74ed6c4882..0000000000
--- a/src/internal/types/testdata/fixedbugs/issue46461a.go
+++ /dev/null
@@ -1,22 +0,0 @@
-// -gotypesalias=1
-
-// Copyright 2021 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.
-
-package p
-
-// test case 1
-type T[U interface{ M() T[U] }] int
-
-type X int
-
-func (X) M() T[X] { return 0 }
-
-// test case 2
-type A[T interface{ A[T] }] interface{}
-
-// test case 3
-type A2[U interface{ A2[U] }] interface{ M() A2[U] }
-
-type I interface{ A2[I]; M() A2[I] }
diff --git a/src/internal/types/testdata/fixedbugs/issue47968.go b/src/internal/types/testdata/fixedbugs/issue47968.go
index e260c63a76..b748651428 100644
--- a/src/internal/types/testdata/fixedbugs/issue47968.go
+++ b/src/internal/types/testdata/fixedbugs/issue47968.go
@@ -1,5 +1,3 @@
-// -gotypesalias=1
-
 // Copyright 2021 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.
diff --git a/src/internal/types/testdata/fixedbugs/issue50729b.go b/src/internal/types/testdata/fixedbugs/issue50729b.go
index bc1f4406e5..76959c2f26 100644
--- a/src/internal/types/testdata/fixedbugs/issue50729b.go
+++ b/src/internal/types/testdata/fixedbugs/issue50729b.go
@@ -1,5 +1,3 @@
-// -gotypesalias=1
-
 // Copyright 2023 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.
diff --git a/src/internal/types/testdata/fixedbugs/issue50779.go b/src/internal/types/testdata/fixedbugs/issue50779.go
index 59c0f2d6a0..6306df65f4 100644
--- a/src/internal/types/testdata/fixedbugs/issue50779.go
+++ b/src/internal/types/testdata/fixedbugs/issue50779.go
@@ -1,5 +1,3 @@
-// -gotypesalias=0
-
 // 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.
@@ -17,7 +15,7 @@ type R[S any, P any] struct{}
 type SR = R[SS, ST]
 
 type SS interface {
-	NSR(any) *SR // ERROR "invalid use of type alias SR in recursive type"
+	NSR(any) *SR
 }
 
 type C interface {
diff --git a/src/internal/types/testdata/fixedbugs/issue50779a.go b/src/internal/types/testdata/fixedbugs/issue50779a.go
deleted file mode 100644
index d0e99058b7..0000000000
--- a/src/internal/types/testdata/fixedbugs/issue50779a.go
+++ /dev/null
@@ -1,25 +0,0 @@
-// -gotypesalias=1
-
-// 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.
-
-package p
-
-type AC interface {
-	C
-}
-
-type ST []int
-
-type R[S any, P any] struct{}
-
-type SR = R[SS, ST]
-
-type SS interface {
-	NSR(any) *SR
-}
-
-type C interface {
-	NSR(any) *SR
-}
diff --git a/src/internal/types/testdata/fixedbugs/issue65854.go b/src/internal/types/testdata/fixedbugs/issue65854.go
index 744777a94f..8fdd3ae94a 100644
--- a/src/internal/types/testdata/fixedbugs/issue65854.go
+++ b/src/internal/types/testdata/fixedbugs/issue65854.go
@@ -1,5 +1,3 @@
-// -gotypesalias=1
-
 // Copyright 2024 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.
diff --git a/src/internal/types/testdata/fixedbugs/issue67628.go b/src/internal/types/testdata/fixedbugs/issue67628.go
index dff1bee4a0..cd45cd61b9 100644
--- a/src/internal/types/testdata/fixedbugs/issue67628.go
+++ b/src/internal/types/testdata/fixedbugs/issue67628.go
@@ -1,5 +1,3 @@
-// -gotypesalias=1
-
 // Copyright 2024 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.
diff --git a/src/internal/types/testdata/fixedbugs/issue67683.go b/src/internal/types/testdata/fixedbugs/issue67683.go
index c9ad5f6788..fbad886331 100644
--- a/src/internal/types/testdata/fixedbugs/issue67683.go
+++ b/src/internal/types/testdata/fixedbugs/issue67683.go
@@ -1,5 +1,3 @@
-// -gotypesalias=1
-
 // Copyright 2024 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.
diff --git a/src/internal/types/testdata/fixedbugs/issue69576.go b/src/internal/types/testdata/fixedbugs/issue69576.go
index fc436bbfd3..1bc9b4ee33 100644
--- a/src/internal/types/testdata/fixedbugs/issue69576.go
+++ b/src/internal/types/testdata/fixedbugs/issue69576.go
@@ -1,5 +1,3 @@
-// -gotypesalias=1
-
 // Copyright 2024 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.
diff --git a/src/internal/types/testdata/fixedbugs/issue69955.go b/src/internal/types/testdata/fixedbugs/issue69955.go
index 68ddf4108c..01a5d95262 100644
--- a/src/internal/types/testdata/fixedbugs/issue69955.go
+++ b/src/internal/types/testdata/fixedbugs/issue69955.go
@@ -1,5 +1,3 @@
-// -gotypesalias=1
-
 // Copyright 2024 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.
diff --git a/src/internal/types/testdata/fixedbugs/issue70417.go b/src/internal/types/testdata/fixedbugs/issue70417.go
index 74bdea3b8a..683df3a503 100644
--- a/src/internal/types/testdata/fixedbugs/issue70417.go
+++ b/src/internal/types/testdata/fixedbugs/issue70417.go
@@ -1,5 +1,3 @@
-// -gotypesalias=1
-
 // Copyright 2024 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.
diff --git a/src/internal/types/testdata/fixedbugs/issue71198.go b/src/internal/types/testdata/fixedbugs/issue71198.go
index 479f8e2b0c..f2dcc9828a 100644
--- a/src/internal/types/testdata/fixedbugs/issue71198.go
+++ b/src/internal/types/testdata/fixedbugs/issue71198.go
@@ -1,5 +1,3 @@
-// -gotypesalias=1
-
 // Copyright 2025 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.
diff --git a/src/internal/types/testdata/fixedbugs/issue75885.go b/src/internal/types/testdata/fixedbugs/issue75885.go
index f0cf4a65ed..77f220b87a 100644
--- a/src/internal/types/testdata/fixedbugs/issue75885.go
+++ b/src/internal/types/testdata/fixedbugs/issue75885.go
@@ -1,5 +1,3 @@
-// -gotypesalias=1
-
 // Copyright 2025 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.
diff --git a/src/internal/types/testdata/spec/receivers.go b/src/internal/types/testdata/spec/receivers.go
index 010c5511c1..0df1bfd6cc 100644
--- a/src/internal/types/testdata/spec/receivers.go
+++ b/src/internal/types/testdata/spec/receivers.go
@@ -1,5 +1,3 @@
-// -gotypesalias=1
-
 // Copyright 2024 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.
diff --git a/src/internal/types/testdata/spec/typeAliases1.23b.go b/src/internal/types/testdata/spec/typeAliases1.23.go
index 8a09899066..061792974d 100644
--- a/src/internal/types/testdata/spec/typeAliases1.23b.go
+++ b/src/internal/types/testdata/spec/typeAliases1.23.go
@@ -1,4 +1,4 @@
-// -lang=go1.23 -gotypesalias=1
+// -lang=go1.23
 
 // Copyright 2024 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
diff --git a/src/internal/types/testdata/spec/typeAliases1.23a.go b/src/internal/types/testdata/spec/typeAliases1.23a.go
deleted file mode 100644
index 0ea21a4e32..0000000000
--- a/src/internal/types/testdata/spec/typeAliases1.23a.go
+++ /dev/null
@@ -1,10 +0,0 @@
-// -lang=go1.23 -gotypesalias=0
-
-// Copyright 2024 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.
-
-package aliasTypes
-
-type _ = int
-type _ /* ERROR "generic type alias requires GODEBUG=gotypesalias=1" */ [P any] = int