[dev.typeparams] cmd/compile/internal/types2: don't permit method calls on ptr to...

Simplify the implementation of asInterface while at it.

For #47031.

Change-Id: Ie7d4fbbab898d961ed3c0b7772ba9604641be13f
Reviewed-on: https://go-review.googlesource.com/c/go/+/332609
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>

diff --git a/src/cmd/compile/internal/types2/lookup.go b/src/cmd/compile/internal/types2/lookup.go
index d59a2f474c6c8005c76bd75c2275da022479e9bd..91be14bde3e9e4879c7ff31d138f556c203b6063 100644 (file)
--- a/src/cmd/compile/internal/types2/lookup.go
+++ b/src/cmd/compile/internal/types2/lookup.go
@@ -73,10 +73,12 @@ func lookupFieldOrMethod(T Type, addressable bool, pkg *Package, name string) (o
 
        typ, isPtr := deref(T)
 
-       // *typ where typ is an interface has no methods.
-       // Be cautious: typ may be nil (issue 39634, crash #3).
-       if typ == nil || isPtr && IsInterface(typ) {
-               return
+       // *typ where typ is an interface or type parameter has no methods.
+       switch under(typ).(type) {
+       case *Interface, *TypeParam:
+               if isPtr {
+                       return
+               }
        }
 
        // Start with typ as single entry at shallowest depth.

diff --git a/src/cmd/compile/internal/types2/testdata/check/issues.go2 b/src/cmd/compile/internal/types2/testdata/check/issues.go2
index 59dd4ae465a64de063d0de978216bde4f82b6baa..88ae294d7c1bbbdb3d5ef16b1423516c66ec9e79 100644 (file)
--- a/src/cmd/compile/internal/types2/testdata/check/issues.go2
+++ b/src/cmd/compile/internal/types2/testdata/check/issues.go2
@@ -24,22 +24,20 @@ func _() {
        eql[io.Reader](nil, nil)
 }
 
-// If we have a receiver of pointer type (below: *T) we must ignore
-// the pointer in the implementation of the method lookup because
-// the type bound of T is an interface and pointer to interface types
-// have no methods and then the lookup would fail.
+// If we have a receiver of pointer to type parameter type (below: *T)
+// we don't have any methods, like for interfaces.
 type C[T any] interface {
     m()
 }
 
 // using type bound C
 func _[T C[T]](x *T) {
-       x.m()
+       x.m /* ERROR x\.m undefined */ ()
 }
 
 // using an interface literal as bound
 func _[T interface{ m() }](x *T) {
-       x.m()
+       x.m /* ERROR x\.m undefined */ ()
 }
 
 func f2[_ interface{ m1(); m2() }]()

diff --git a/src/cmd/compile/internal/types2/testdata/fixedbugs/issue47031.go2 b/src/cmd/compile/internal/types2/testdata/fixedbugs/issue47031.go2
new file mode 100644 (file)
index 0000000..b184f9b
--- /dev/null
+++ b/src/cmd/compile/internal/types2/testdata/fixedbugs/issue47031.go2
@@ -0,0 +1,20 @@
+// 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 Mer interface { M() }
+
+func F[T Mer](p *T) {
+       p.M /* ERROR p\.M undefined */ ()
+}
+
+type MyMer int
+
+func (MyMer) M() {}
+
+func _() {
+       F(new(MyMer))
+       F[Mer](nil)
+}

diff --git a/src/cmd/compile/internal/types2/type.go b/src/cmd/compile/internal/types2/type.go
index e3f63f63b558afc7008a8c62c86dbbeb6b65a711..c2da97605b133e1dcef6d5289c9df028ddf30920 100644 (file)
--- a/src/cmd/compile/internal/types2/type.go
+++ b/src/cmd/compile/internal/types2/type.go
@@ -112,11 +112,6 @@ func asSignature(t Type) *Signature {
        return op
 }
 
-func asInterface(t Type) *Interface {
-       op, _ := optype(t).(*Interface)
-       return op
-}
-
 func asMap(t Type) *Map {
        op, _ := optype(t).(*Map)
        return op
@@ -127,10 +122,16 @@ func asChan(t Type) *Chan {
        return op
 }
 
-// If the argument to asNamed and asTypeParam is of the respective types
+// If the argument to asInterface, asNamed, or asTypeParam is of the respective type
 // (possibly after expanding an instance type), these methods return that type.
 // Otherwise the result is nil.
 
+// asInterface does not need to look at optype (type sets don't contain interfaces)
+func asInterface(t Type) *Interface {
+       u, _ := under(t).(*Interface)
+       return u
+}
+
 func asNamed(t Type) *Named {
        e, _ := expand(t).(*Named)
        return e