go/types: temporarily pin the Checker to Interface during checking

While type checking expressions involving interface types, it is
possible that their type set is used before delayed actions are
processed. As a result, computeInterfaceTypeSet is called with a nil
checker, and errors in the interface type definition result in panics
(see #48234).

To avoid the panics, store a *Checker on Interface for use in between
checking of the interface type expression and processing of delayed
actions.

Fixes #48234

Change-Id: I5509bc1c01b55edac52446b9e075fbe8fcc01874
Reviewed-on: https://go-review.googlesource.com/c/go/+/348371
Trust: Robert Findley <rfindley@google.com>
Run-TryBot: Robert Findley <rfindley@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>

diff --git a/src/go/types/interface.go b/src/go/types/interface.go
index 2211e37c5981771a5adfdd7e10279003ab105962..c67aca7a2012427203fbeb7a566031587f5d80c4 100644 (file)
--- a/src/go/types/interface.go
+++ b/src/go/types/interface.go
@@ -14,6 +14,7 @@ import (
 
 // An Interface represents an interface type.
 type Interface struct {
+       check     *Checker     // for error reporting; nil once type set is computed
        obj       *TypeName    // type name object defining this interface; or nil (for better error messages)
        methods   []*Func      // ordered list of explicitly declared methods
        embeddeds []Type       // ordered list of explicitly embedded elements
@@ -24,7 +25,7 @@ type Interface struct {
 }
 
 // typeSet returns the type set for interface t.
-func (t *Interface) typeSet() *_TypeSet { return computeInterfaceTypeSet(nil, token.NoPos, t) }
+func (t *Interface) typeSet() *_TypeSet { return computeInterfaceTypeSet(t.check, token.NoPos, t) }
 
 // emptyInterface represents the empty (completed) interface
 var emptyInterface = Interface{complete: true, tset: &topTypeSet}
@@ -220,7 +221,7 @@ func (check *Checker) interfaceType(ityp *Interface, iface *ast.InterfaceType, d
        }
 
        // All methods and embedded elements for this interface are collected;
-       // i.e., this interface is may be used in a type set computation.
+       // i.e., this interface may be used in a type set computation.
        ityp.complete = true
 
        if len(ityp.methods) == 0 && len(ityp.embeddeds) == 0 {
@@ -236,7 +237,15 @@ func (check *Checker) interfaceType(ityp *Interface, iface *ast.InterfaceType, d
        // Compute type set with a non-nil *Checker as soon as possible
        // to report any errors. Subsequent uses of type sets will use
        // this computed type set and won't need to pass in a *Checker.
-       check.later(func() { computeInterfaceTypeSet(check, iface.Pos(), ityp) })
+       //
+       // Pin the checker to the interface type in the interim, in case the type set
+       // must be used before delayed funcs are processed (see issue #48234).
+       // TODO(rfindley): clean up use of *Checker with computeInterfaceTypeSet
+       ityp.check = check
+       check.later(func() {
+               computeInterfaceTypeSet(check, iface.Pos(), ityp)
+               ityp.check = nil
+       })
 }
 
 func flattenUnion(list []ast.Expr, x ast.Expr) []ast.Expr {

diff --git a/src/go/types/sizeof_test.go b/src/go/types/sizeof_test.go
index c2f5b3c3331e83a43642a7c1ae882830ee5af425..f64f732884609d50934930e621ce05887f81da61 100644 (file)
--- a/src/go/types/sizeof_test.go
+++ b/src/go/types/sizeof_test.go
@@ -27,7 +27,7 @@ func TestSizeof(t *testing.T) {
                {Tuple{}, 12, 24},
                {Signature{}, 28, 56},
                {Union{}, 16, 32},
-               {Interface{}, 40, 80},
+               {Interface{}, 44, 88},
                {Map{}, 16, 32},
                {Chan{}, 12, 24},
                {Named{}, 72, 136},

diff --git a/src/go/types/testdata/fixedbugs/issue48234.go2 b/src/go/types/testdata/fixedbugs/issue48234.go2
new file mode 100644 (file)
index 0000000..e069930
--- /dev/null
+++ b/src/go/types/testdata/fixedbugs/issue48234.go2
@@ -0,0 +1,10 @@
+// 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
+
+var _ = interface{
+       m()
+       m /* ERROR "duplicate method" */ ()
+}(nil)

diff --git a/src/go/types/universe.go b/src/go/types/universe.go
index a2acfb5f69dc3850d7e513fcfb47981f96066d2c..6045c61c301297a7c88ac85d7991dcd441781942 100644 (file)
--- a/src/go/types/universe.go
+++ b/src/go/types/universe.go
@@ -89,7 +89,7 @@ func defPredeclaredTypes() {
                res := NewVar(token.NoPos, nil, "", Typ[String])
                sig := NewSignature(nil, nil, NewTuple(res), false)
                err := NewFunc(token.NoPos, nil, "Error", sig)
-               ityp := &Interface{obj, []*Func{err}, nil, nil, true, nil}
+               ityp := &Interface{nil, obj, []*Func{err}, nil, nil, true, nil}
                computeInterfaceTypeSet(nil, token.NoPos, ityp) // prevent races due to lazy computation of tset
                typ := NewNamed(obj, ityp, nil)
                sig.recv = NewVar(token.NoPos, nil, "", typ)
@@ -100,7 +100,7 @@ func defPredeclaredTypes() {
        {
                obj := NewTypeName(token.NoPos, nil, "comparable", nil)
                obj.setColor(black)
-               ityp := &Interface{obj, nil, nil, nil, true, &_TypeSet{true, nil, allTermlist}}
+               ityp := &Interface{nil, obj, nil, nil, nil, true, &_TypeSet{true, nil, allTermlist}}
                NewNamed(obj, ityp, nil)
                def(obj)
        }