Why doesnt this give a compile error, is it a bug in golang or do I miss something?
intPadded := fmt.Sprintf("%09d", "i am a string" )
fmt.Println("bah" + intPadded)
when executed it gives
bah%!d(string=i am a string)
"If an invalid argument is given for a verb, such as providing a string to %d, the generated string will contain a description of the problem" per http://golang.org/pkg/fmt/
It doesn't give a compile-time error because there is no compile-time error. fmt.Sprintf() is defined as taking ...interface{} for its last argument, which is valid for any sequence of types. The checking is done only at runtime.
It's your bug. The compiler can only check that the fmt.Sprintf arguments have the proper type; all types implement the empty interface. Use the Go vet command.
func Sprintf(format string, a ...interface{}) stringSprintf formats according to a format specifier and returns the resulting string.
An interface type specifies a method set called its interface. A variable of interface type can store a value of any type with a method set that is any superset of the interface. Such a type is said to implement the interface.
A type implements any interface comprising any subset of its methods and may therefore implement several distinct interfaces. For instance, all types implement the empty interface:
interface{}Vet examines Go source code and reports suspicious constructs, such as Printf calls whose arguments do not align with the format string.