^Syntax
LiteralExpression :
      CHAR_LITERAL
   | STRING_LITERAL
   | RAW_STRING_LITERAL
   | BYTE_LITERAL
   | BYTE_STRING_LITERAL
   | RAW_BYTE_STRING_LITERAL
   | INTEGER_LITERAL
   | FLOAT_LITERAL
   | BOOLEAN_LITERAL

A literal expression consists of one of the literal forms described earlier. It directly describes a number, character, string, or boolean value.

#![allow(unused_variables)]
fn main() {
"hello";   // string type
'5';       // character type
5;         // integer type
}