From 5ba51116ee39a14a475d7f92a16dd676fccd0729 Mon Sep 17 00:00:00 2001
From: Rob Pike <r@golang.org>
Date: Tue, 30 Jul 2013 14:00:52 +1000
Subject: [PATCH] go.tools/cmd/vet: treat arrays like slices in the printf
 checks. The analysis for types.Array was just missing. It's the same as a
 slice, but we can't share code easily because the types differ, so we just
 dup it.

R=dsymonds
CC=golang-dev
https://golang.org/cl/12041045
---
 cmd/vet/testdata/print.go | 21 +++++++++++++++++++++
 cmd/vet/types.go          | 15 ++++++++++++---
 2 files changed, 33 insertions(+), 3 deletions(-)

diff --git a/cmd/vet/testdata/print.go b/cmd/vet/testdata/print.go
index f41e7543..0440e348 100644
--- a/cmd/vet/testdata/print.go
+++ b/cmd/vet/testdata/print.go
@@ -79,9 +79,15 @@ func PrintfTests() {
 	fmt.Printf("%X %X %X %X", 3, i, "hi", s)
 	fmt.Printf("%.*s %d %g", 3, "hi", 23, 2.3)
 	fmt.Printf("%s", &stringerv)
+	fmt.Printf("%v", &stringerv)
 	fmt.Printf("%T", &stringerv)
 	fmt.Printf("%v", notstringerv)
 	fmt.Printf("%T", notstringerv)
+	fmt.Printf("%q", stringerarrayv)
+	fmt.Printf("%v", stringerarrayv)
+	fmt.Printf("%s", stringerarrayv)
+	fmt.Printf("%v", notstringerarrayv)
+	fmt.Printf("%T", notstringerarrayv)
 	fmt.Printf("%*%", 2) // Ridiculous but allowed.
 
 	fmt.Printf("%g", 1+2i)
@@ -111,6 +117,9 @@ func PrintfTests() {
 	fmt.Printf("%t", stringerv)                // ERROR "arg stringerv for printf verb %t of wrong type"
 	fmt.Printf("%q", notstringerv)             // ERROR "arg notstringerv for printf verb %q of wrong type"
 	fmt.Printf("%t", notstringerv)             // ERROR "arg notstringerv for printf verb %t of wrong type"
+	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("%.*s %d %g", 3, "hi", 23, 'x') // ERROR "arg 'x' for printf verb %g of wrong type"
 	fmt.Println()                              // not an error
 	fmt.Println("%s", "hi")                    // ERROR "possible formatting directive in Println call"
@@ -206,3 +215,15 @@ func (*stringer) Warnf(int, string, ...interface{}) string {
 type notstringer struct{}
 
 var notstringerv notstringer
+
+type stringerarray [4]float64
+
+func (stringerarray) String() string {
+	return "string"
+}
+
+var stringerarrayv stringerarray
+
+type notstringerarray [4]float64
+
+var notstringerarrayv notstringerarray
diff --git a/cmd/vet/types.go b/cmd/vet/types.go
index 263f8534..9fd00ee7 100644
--- a/cmd/vet/types.go
+++ b/cmd/vet/types.go
@@ -98,18 +98,27 @@ func (f *File) matchArgType(t printfArgType, typ types.Type, arg ast.Expr) bool
 		return t&argPointer != 0
 
 	case *types.Map:
-		// Recurse: map[int]int matches %d.
+		// Recur: map[int]int matches %d.
 		return t&argPointer != 0 ||
 			(f.matchArgType(t, typ.Key(), arg) && f.matchArgType(t, typ.Elem(), arg))
 
 	case *types.Chan:
 		return t&argPointer != 0
 
-	case *types.Slice:
+	case *types.Array:
+		// Same as slice.
 		if types.IsIdentical(typ.Elem().Underlying(), types.Typ[types.Byte]) && t&argString != 0 {
 			return true // %s matches []byte
 		}
-		// Recurse: []int matches %d.
+		// Recur: []int matches %d.
+		return t&argPointer != 0 || f.matchArgType(t, typ.Elem(), arg)
+
+	case *types.Slice:
+		// Same as array.
+		if types.IsIdentical(typ.Elem().Underlying(), types.Typ[types.Byte]) && t&argString != 0 {
+			return true // %s matches []byte
+		}
+		// Recur: []int matches %d.
 		return t&argPointer != 0 || f.matchArgType(t, typ.Elem(), arg)
 
 	case *types.Pointer: