go/types: don't panic if targs don't match tparams when substituting

Invalid code may produce instances where the number of type arguments
does not match the number of type parameters. Such code will cause an
error, but should not cause a panic when substituting in those invalid
instances.

Fixes #48529

Change-Id: Ie5ff5ace55921540a7224cc5022ef9ff7649361a
Reviewed-on: https://go-review.googlesource.com/c/go/+/351337
Trust: Robert Findley <rfindley@google.com>
Run-TryBot: Robert Findley <rfindley@google.com>
Reviewed-by: Robert Griesemer <gri@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>

diff --git a/src/go/types/named.go b/src/go/types/named.go
index 07c837d14a44f6d694a4e323bb50093e7f2b9208..d29c67d4eb3f618f03c2dd0d5a9098d7534e1efc 100644 (file)
--- a/src/go/types/named.go
+++ b/src/go/types/named.go
@@ -332,7 +332,7 @@ func (check *Checker) completeMethod(env *Environment, m *Func) {
 // TODO(rfindley): eliminate this function or give it a better name.
 func safeUnderlying(typ Type) Type {
        if t, _ := typ.(*Named); t != nil {
-               return t.resolve(nil).underlying
+               return t.underlying
        }
        return typ.Underlying()
 }

diff --git a/src/go/types/subst.go b/src/go/types/subst.go
index 999099572c7539cf181c0c291673550a172ec2f1..25629dca8ac541cc7b294790aae51c6f716e28d1 100644 (file)
--- a/src/go/types/subst.go
+++ b/src/go/types/subst.go
@@ -177,7 +177,9 @@ func (subst *subster) typ(typ Type) Type {
                }
 
                var newTArgs []Type
-               assert(t.targs.Len() == t.orig.TypeParams().Len())
+               if t.targs.Len() != t.orig.TypeParams().Len() {
+                       return Typ[Invalid] // error reported elsewhere
+               }
 
                // already instantiated
                dump(">>> %s already instantiated", t)

diff --git a/src/go/types/testdata/fixedbugs/issue46461.go2 b/src/go/types/testdata/fixedbugs/issue46461.go2
new file mode 100644 (file)
index 0000000..bfeaf3a
--- /dev/null
+++ b/src/go/types/testdata/fixedbugs/issue46461.go2
@@ -0,0 +1,11 @@
+// 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[U interface{ M() T[U] }] int
+
+type X int
+
+func (X) M() T[X] { return 0 }

diff --git a/src/go/types/testdata/fixedbugs/issue48529.go2 b/src/go/types/testdata/fixedbugs/issue48529.go2
new file mode 100644 (file)
index 0000000..4f92dec
--- /dev/null
+++ b/src/go/types/testdata/fixedbugs/issue48529.go2
@@ -0,0 +1,11 @@
+// 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[U interface{ M() T /* ERROR "got 2 arguments but 1 type parameters" */ [U, int] }] int
+
+type X int
+
+func (X) M() T[X] { return 0 }