From 7517d8bae3f41c96cb511cf241a14fd807a2e103 Mon Sep 17 00:00:00 2001
From: Robert Griesemer <gri@golang.org>
Date: Tue, 18 Jun 2013 15:34:12 -0700
Subject: [PATCH] go.tools/go/types: catch cycles in function declarations

Fixes golang/go#5217.

R=adonovan
CC=golang-dev
https://golang.org/cl/10402044
---
 go/types/resolver.go         |  7 ++++---
 go/types/testdata/decls0.src | 12 ++++++++++++
 2 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/go/types/resolver.go b/go/types/resolver.go
index cb9caaa3..ac47ddde 100644
--- a/go/types/resolver.go
+++ b/go/types/resolver.go
@@ -347,7 +347,7 @@ func (check *checker) declareObject(obj Object, cycleOk bool) {
 	case *TypeName:
 		check.declareType(obj, d.typ, cycleOk)
 	case *Func:
-		check.declareFunc(obj, cycleOk)
+		check.declareFunc(obj)
 	default:
 		unreachable()
 	}
@@ -525,12 +525,13 @@ func (check *checker) declareType(obj *TypeName, typ ast.Expr, cycleOk bool) {
 	}
 }
 
-func (check *checker) declareFunc(obj *Func, cycleOk bool) {
+func (check *checker) declareFunc(obj *Func) {
 	fdecl := obj.decl
 	// methods are typechecked when their receivers are typechecked
 	// TODO(gri) there is no reason to make this a special case: receivers are simply parameters
 	if fdecl.Recv == nil {
-		sig := check.typ(fdecl.Type, cycleOk).(*Signature)
+		obj.typ = Typ[Invalid] // guard against cycles
+		sig := check.typ(fdecl.Type, false).(*Signature)
 		if obj.name == "init" && (sig.params.Len() > 0 || sig.results.Len() > 0) {
 			check.errorf(fdecl.Pos(), "func init must have no arguments and no return values")
 			// ok to continue
diff --git a/go/types/testdata/decls0.src b/go/types/testdata/decls0.src
index fe7995b9..f8a50482 100644
--- a/go/types/testdata/decls0.src
+++ b/go/types/testdata/decls0.src
@@ -186,6 +186,18 @@ type (
 	Last int
 )
 
+// cycles in function/method declarations
+// (test cases for issue 5217 and variants)
+func f1(x f1 /* ERROR "not a type" */ ) {}
+func f2(x *f2 /* ERROR "cannot indirect" */ ) {}
+func f3() (x f3 /* ERROR "not a type" */ ) { return }
+func f4() (x *f4 /* ERROR "cannot indirect" */ ) { return }
+
+func (S0) m1(x S0 /* ERROR "field or method" */ .m1) {}
+func (S0) m2(x *S0 /* ERROR "field or method" */ .m2) {}
+func (S0) m3() (x S0 /* ERROR "field or method" */ .m3) { return }
+func (S0) m4() (x *S0 /* ERROR "field or method" */ .m4) { return }
+
 // interfaces may have blank methods
 type BlankI interface {
 	_()