print the value using (in effect) %v when Printf is given mismatched args for its format

Printf("%s", 2) gives %s(int=2)

R=rsc
DELTA=12  (10 added, 0 deleted, 2 changed)
OCL=34042
CL=34044

src/pkg/fmt/fmt_test.go

@@ -85,6 +85,10 @@ var fmttests = []fmtTest{
 	fmtTest{ "%v",		&array,			"&[1 2 3 4 5]" },
 	fmtTest{ "%v",		&iarray,			"&[1 hello 2.5 <nil>]" },
 
+	// erroneous formats
+	fmtTest{ "",		2,			"?(extra int=2)" },
+	fmtTest{ "%d",		"hello",		"%d(string=hello)%" },
+
 	// old test/fmt_test.go
 	fmtTest{ "%d",		1234,			"1234" },
 	fmtTest{ "%d",		-1234,			"-1234" },

src/pkg/fmt/print.go

@@ -700,14 +700,20 @@ func (p *pp) doprintf(format string, v *reflect.StructValue) {
 
 			default:
 			badtype:
-				s = "%" + string(c) + "(" + field.Type().String() + ")%";
+				s = "%" + string(c) + "(" + field.Type().String() + "=";
+				p.addstr(s);
+				p.printField(field);
+				s= ")%";
 		}
 		p.addstr(s);
 	}
 	if fieldnum < v.NumField() {
 		p.addstr("?(extra ");
 		for ; fieldnum < v.NumField(); fieldnum++ {
-			p.addstr(getField(v, fieldnum).Type().String());
+			field := getField(v, fieldnum);
+			p.addstr(field.Type().String());
+			p.addstr("=");
+			p.printField(field);
 			if fieldnum + 1 < v.NumField() {
 				p.addstr(", ");
 			}