Function is_default_for_syntax 

fn is_default_for_syntax(lit: &LiteralType) -> bool

Whether this type is the default interpretation for its value syntax.

Each literal value syntax has a default type that the parser assumes when no explicit type suffix is present:

• true/false → boolean
• bare integers (42) → i64
• bare floats (3.19) → fp64
• single-quoted strings ('hello') → string
• hex literals (0x...) → binary

Non-default types (e.g., i32, fp32, date) always need an explicit suffix to distinguish them from the default.