[dev.cmdgo] all: merge master (67f7e16) into dev.cmdgodev.cmdgo

Merge List:

+ 2021-08-27 67f7e16bcc encoding/gob: optimize decoding of []byte
+ 2021-08-27 2c60a99f72 cmd/compile/internal/syntax: make valid type parameter list in presence of errors
+ 2021-08-27 d350a66532 cmd/compile: eagerly CalcStructSize for synthetic ABI types
+ 2021-08-27 d7e2e2ec2b cmd/compile: delay fillinMethods to deal with mutually-recursive types
+ 2021-08-27 c927599783 cmd/compile: eliminate repetitive code
+ 2021-08-27 62f88b6dc8 cmd/compile: add types.RecalcSize
+ 2021-08-27 e7eee5e265 cmd/compile: remove ssagen/pgen_test.go
+ 2021-08-27 f153b6739b cmd/compile: use typecheck.InitUniverse in unit tests
+ 2021-08-26 967a8017f7 cmd/compile: move types init code into package types
+ 2021-08-26 af80af22b5 cmd/compile/internal/types2: do not declare new methods on instantiated types
+ 2021-08-26 03db2c2413 cmd/compile/internal/types2: implement TypeList.String (debugging support)
+ 2021-08-26 c9e05fdcf7 cmd/compile: fix reference to generic type needed by crawler
+ 2021-08-26 eb6a07fcf9 cmd/compile: unexport Type.Vargen
+ 2021-08-26 3836983779 cmd/compile/internal/types: unexport Type.Extra
+ 2021-08-26 1f8d4562de cmd/compile: change typecheck.iscmp into ir.Op.IsCmp

Change-Id: I95c040a0e984a13a3b12c50458148007221ee300

6 files changed, 50 insertions, 8 deletions

diff --git a/src/cmd/compile/internal/types2/instantiate.go b/src/cmd/compile/internal/types2/instantiate.go
index f9cde24dfc..4113d248b8 100644
--- a/src/cmd/compile/internal/types2/instantiate.go
+++ b/src/cmd/compile/internal/types2/instantiate.go
@@ -75,7 +75,7 @@ func Instantiate(env *Environment, typ Type, targs []Type, validate bool) (Type,
 func (check *Checker) instantiate(pos syntax.Pos, typ Type, targs []Type, posList []syntax.Pos) (res Type) {
 	assert(check != nil)
 	if check.conf.Trace {
-		check.trace(pos, "-- instantiating %s with %s", typ, typeListString(targs))
+		check.trace(pos, "-- instantiating %s with %s", typ, NewTypeList(targs))
 		check.indent++
 		defer func() {
 			check.indent--
diff --git a/src/cmd/compile/internal/types2/signature.go b/src/cmd/compile/internal/types2/signature.go
index d28e7b8944..ddad1f0311 100644
--- a/src/cmd/compile/internal/types2/signature.go
+++ b/src/cmd/compile/internal/types2/signature.go
@@ -132,7 +132,7 @@ func (check *Checker) funcType(sig *Signature, recvPar *syntax.Field, tparams []
 				// Also: Don't report an error via genericType since it will be reported
 				//       again when we type-check the signature.
 				// TODO(gri) maybe the receiver should be marked as invalid instead?
-				if recv := asNamed(check.genericType(rname, false)); recv != nil {
+				if recv, _ := check.genericType(rname, false).(*Named); recv != nil {
 					recvTParams = recv.TParams().list()
 				}
 			}
@@ -211,6 +211,12 @@ func (check *Checker) funcType(sig *Signature, recvPar *syntax.Field, tparams []
 			switch T := rtyp.(type) {
 			case *Named:
 				T.expand(nil)
+				// The receiver type may be an instantiated type referred to
+				// by an alias (which cannot have receiver parameters for now).
+				if T.TArgs() != nil && sig.RParams() == nil {
+					check.errorf(recv.pos, "cannot define methods on instantiated type %s", recv.typ)
+					break
+				}
 				// spec: "The type denoted by T is called the receiver base type; it must not
 				// be a pointer or interface type and it must be declared in the same package
 				// as the method."
diff --git a/src/cmd/compile/internal/types2/subst.go b/src/cmd/compile/internal/types2/subst.go
index ff8dd13b6d..7c33e7ade4 100644
--- a/src/cmd/compile/internal/types2/subst.go
+++ b/src/cmd/compile/internal/types2/subst.go
@@ -281,12 +281,6 @@ func instantiatedHash(typ *Named, targs []Type) string {
 	return string(res[:i])
 }
 
-func typeListString(list []Type) string {
-	var buf bytes.Buffer
-	writeTypeList(&buf, list, nil, nil)
-	return buf.String()
-}
-
 // typOrNil is like typ but if the argument is nil it is replaced with Typ[Invalid].
 // A nil type may appear in pathological cases such as type T[P any] []func(_ T([]_))
 // where an array/slice element is accessed before it is set up.
diff --git a/src/cmd/compile/internal/types2/testdata/fixedbugs/issue47968.go2 b/src/cmd/compile/internal/types2/testdata/fixedbugs/issue47968.go2
new file mode 100644
index 0000000000..bbbe6805f2
--- /dev/null
+++ b/src/cmd/compile/internal/types2/testdata/fixedbugs/issue47968.go2
@@ -0,0 +1,21 @@
+// 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
+
+type T[P any] struct{}
+
+func (T[P]) m1()
+
+type A1 = T
+
+func (A1[P]) m2() {}
+
+type A2 = T[int]
+
+func (A2 /* ERROR cannot define methods on instantiated type T\[int\] */) m3()   {}
+func (_ /* ERROR cannot define methods on instantiated type T\[int\] */ A2) m4() {}
+
+func (T[int]) m5()                                     {} // int is the type parameter name, not an instantiation
+func (T[* /* ERROR must be an identifier */ int]) m6() {} // syntax error
diff --git a/src/cmd/compile/internal/types2/testdata/fixedbugs/issue47996.go2 b/src/cmd/compile/internal/types2/testdata/fixedbugs/issue47996.go2
new file mode 100644
index 0000000000..56e90942ab
--- /dev/null
+++ b/src/cmd/compile/internal/types2/testdata/fixedbugs/issue47996.go2
@@ -0,0 +1,8 @@
+// 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
+
+// don't crash
+func T /* ERROR missing */ [P /* ERROR named */ ] m /* ERROR m */ () /* ERROR \) */ { /* ERROR { */ } /* ERROR } */
diff --git a/src/cmd/compile/internal/types2/typelists.go b/src/cmd/compile/internal/types2/typelists.go
index 3258a5e9f8..c3befb077f 100644
--- a/src/cmd/compile/internal/types2/typelists.go
+++ b/src/cmd/compile/internal/types2/typelists.go
@@ -4,6 +4,8 @@
 
 package types2
 
+import "bytes"
+
 // TParamList holds a list of type parameters.
 type TParamList struct{ tparams []*TypeParam }
 
@@ -52,6 +54,17 @@ func (l *TypeList) list() []Type {
 	return l.types
 }
 
+func (l *TypeList) String() string {
+	if l == nil || len(l.types) == 0 {
+		return "[]"
+	}
+	var buf bytes.Buffer
+	buf.WriteByte('[')
+	writeTypeList(&buf, l.types, nil, nil)
+	buf.WriteByte(']')
+	return buf.String()
+}
+
 // ----------------------------------------------------------------------------
 // Implementation