go.tools/go/types: add test cases for pending issues

The gc compiler is inconsistent how it handles method
"mentions" with respect to initialization cycle detection
(see issue 6703 for details). Pending a spec clarification,
this CL assumes that for a method to be "mentioned", it
must be mentioned as a method expression rather than a
method value (closer in intent to "syntactic" mention).

R=adonovan
CC=golang-dev
https://golang.org/cl/22050044

go/types/call.go

@@ -350,9 +350,6 @@ func (check *checker) selector(x *operand, e *ast.SelectorExpr) {
 			isVariadic: sig.isVariadic,
 		}
 
-		// TODO(gri) move this into exprInternal's call of check.selector
-		// since that's the only place where we need to record a dependency
-		// (requires that operands know method objects)
 		check.addDeclDep(m)
 
 	} else {
@@ -418,9 +415,6 @@ func (check *checker) selector(x *operand, e *ast.SelectorExpr) {
 			sig.recv = nil
 			x.typ = &sig
 
-			// TODO(gri) see comment above for addDeclDep
-			check.addDeclDep(obj)
-
 		default:
 			unreachable()
 		}

go/types/check_test.go

@@ -53,6 +53,7 @@ var tests = [][]string{
 	{"testdata/cycles3.src"},
 	{"testdata/cycles4.src"},
 	{"testdata/init0.src"},
+	{"testdata/init1.src"},
 	{"testdata/decls0.src"},
 	{"testdata/decls1.src"},
 	{"testdata/decls2a.src", "testdata/decls2b.src"},

go/types/stdlib_test.go

@@ -125,6 +125,7 @@ func TestStdtest(t *testing.T) {
 func TestStdfixed(t *testing.T) {
 	testTestDir(t, filepath.Join(runtime.GOROOT(), "test", "fixedbugs"),
 		"bug248.go", "bug302.go", "bug369.go", // complex test instructions - ignore
+		"bug459.go",    // incorrect test - see issue 6793 (pending spec clarification)
 		"issue3924.go", // incorrect test - see issue 6671
 		"issue4847.go", // TODO(gri) initialization cycle error not found
 	)

go/types/testdata/init0.src

@@ -68,12 +68,11 @@ func (T1) m() bool { _ = x11; return false }
 
 var x11 /* ERROR initialization cycle */ = T1.m(T1{})
 
-// cycles via method values
+// no cycles via method values
 
 type T2 struct{}
 
 func (T2) m() bool { _ = x12; return false }
 
 var t1 T2
-var x12 /* ERROR initialization cycle */ = t1.m
-
+var x12 = t1.m

go/types/testdata/init1.src

@@ -0,0 +1,73 @@
+// Copyright 2013 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.
+
+// initialization cycles
+
+package init1
+
+// issue 6683 (marked as WorkingAsIntended)
+
+type T0 struct{}
+
+func (T0) m() int { return y0 }
+
+var x0 = T0{}
+
+var y0 = x0.m() // no cycle reported
+
+type T1 struct{}
+
+func (T1) m() int { return y1 }
+
+var x1 interface {
+	m() int
+} = T1{}
+
+var y1 = x1.m() // no cycle reported
+
+// issue 6703 (modified)
+
+var x2 /* ERROR initialization cycle */ = T2.m
+
+var y2 = x2
+
+type T2 struct{}
+
+func (T2) m() int {
+	_ = y2
+	return 0
+}
+
+var x3 /* ERROR initialization cycle */ = T3.m(T3{}) // <<<< added (T3{})
+
+var y3 = x3
+
+type T3 struct{}
+
+func (T3) m() int {
+	_ = y3
+	return 0
+}
+
+var x4 = T4{}.m // <<<< added {}
+
+var y4 = x4
+
+type T4 struct{}
+
+func (T4) m() int {
+	_ = y4
+	return 0
+}
+
+var x5 = T5{}.m() // <<<< added ()
+
+var y5 = x5
+
+type T5 struct{}
+
+func (T5) m() int {
+	_ = y5
+	return 0
+}

go/types/typexpr.go

@@ -89,9 +89,6 @@ func (check *checker) ident(x *operand, e *ast.Ident, def *Named, cycleOk bool)
 	case *Var:
 		obj.used = true
 		x.mode = variable
-		// TODO(gri) move this into exprInternal's call of check.ident
-		// since that's the only place where we need to record a dependency
-		// (requires that operands know variable objects)
 		if typ != Typ[Invalid] {
 			check.addDeclDep(obj)
 		}
@@ -99,7 +96,6 @@ func (check *checker) ident(x *operand, e *ast.Ident, def *Named, cycleOk bool)
 	case *Func:
 		obj.used = true
 		x.mode = value
-		// TODO(gri) see comment above for addDeclDep
 		if typ != Typ[Invalid] {
 			check.addDeclDep(obj)
 		}