From d4c8d5dae38efb18e645ff140486f33b8860a17a Mon Sep 17 00:00:00 2001
From: David Symonds <dsymonds@golang.org>
Date: Thu, 13 Mar 2014 11:19:34 +1100
Subject: [PATCH] vet: Broaden suppression of recursive stringer warning.

Updates golang/go#6212.

LGTM=r, gri
R=r, gri
CC=golang-codereviews
https://golang.org/cl/75130043
---
 cmd/vet/print.go          |  9 +++++++++
 cmd/vet/testdata/print.go |  2 +-
 cmd/vet/types.go          | 17 +++++++----------
 3 files changed, 17 insertions(+), 11 deletions(-)

diff --git a/cmd/vet/print.go b/cmd/vet/print.go
index b47dbd02a3..38617eccde 100644
--- a/cmd/vet/print.go
+++ b/cmd/vet/print.go
@@ -408,6 +408,15 @@ func (f *File) recursiveStringer(e ast.Expr) bool {
 			obj = id.Obj
 		}
 	}
+
+	// It's unlikely to be a recursive stringer if it has a Format method.
+	if typ := f.pkg.types[e].Type; typ != nil {
+		// Not a perfect match; see issue 6259.
+		if f.hasMethod(typ, "Format") {
+			return false
+		}
+	}
+
 	// We compare the underlying Object, which checks that the identifier
 	// is the one we declared as the receiver for the String method in
 	// which this printf appears.
diff --git a/cmd/vet/testdata/print.go b/cmd/vet/testdata/print.go
index 1dd58d9f69..ab015af653 100644
--- a/cmd/vet/testdata/print.go
+++ b/cmd/vet/testdata/print.go
@@ -123,7 +123,7 @@ func PrintfTests() {
 	fmt.Printf("%t", stringerarrayv)           // ERROR "arg stringerarrayv for printf verb %t of wrong type"
 	fmt.Printf("%t", notstringerarrayv)        // ERROR "arg notstringerarrayv for printf verb %t of wrong type"
 	fmt.Printf("%q", notstringerarrayv)        // ERROR "arg notstringerarrayv for printf verb %q of wrong type"
-	fmt.Printf("%d", Formatter(true))          // ERROR "arg Formatter\(true\) for printf verb %d of wrong type"
+	fmt.Printf("%d", Formatter(true))          // correct (the type is responsible for formatting)
 	fmt.Printf("%s", nonemptyinterface)        // correct (the dynamic type of nonemptyinterface may be a stringer)
 	fmt.Printf("%.*s %d %g", 3, "hi", 23, 'x') // ERROR "arg 'x' for printf verb %g of wrong type"
 	fmt.Println()                              // not an error
diff --git a/cmd/vet/types.go b/cmd/vet/types.go
index 2cf4de4a92..6afc6ab975 100644
--- a/cmd/vet/types.go
+++ b/cmd/vet/types.go
@@ -103,7 +103,7 @@ func (f *File) matchArgTypeInternal(t printfArgType, typ types.Type, arg ast.Exp
 	// if its method set contains a Format function. We could do better,
 	// even now, but we don't need to be 100% accurate. Wait for 6259 to
 	// be fixed instead. TODO.
-	if hasMethod(typ, "Format") {
+	if f.hasMethod(typ, "Format") {
 		return true
 	}
 	// If we can use a string, might arg (dynamically) implement the Stringer or Error interface?
@@ -313,13 +313,10 @@ func (f *File) isErrorMethodCall(call *ast.CallExpr) bool {
 
 // hasMethod reports whether the type contains a method with the given name.
 // It is part of the workaround for Formatters and should be deleted when
-// that workaround is no longer necessary. TODO: delete when fixed.
-func hasMethod(typ types.Type, name string) bool {
-	set := types.NewMethodSet(typ)
-	for i := 0; i < set.Len(); i++ {
-		if set.At(i).Obj().Name() == name {
-			return true
-		}
-	}
-	return false
+// that workaround is no longer necessary.
+// TODO: This could be better once issue 6259 is fixed.
+func (f *File) hasMethod(typ types.Type, name string) bool {
+	obj, _, _ := types.LookupFieldOrMethod(typ, f.pkg.typesPkg, name)
+	_, ok := obj.(*types.Func)
+	return ok
 }