Identifiers

Identifiers are names for variables, functions, classes, etc.

Syntax

identifier ::= (letter | '_') (letter | digit | '_')*
letter     ::= 'a'..'z' | 'A'..'Z'
digit      ::= '0'..'9'

Rules

• Must start with letter or underscore
• Can contain letters, digits, and underscores
• Case-sensitive: myVar, myvar, and MYVAR are different identifiers
• Cannot be a keyword
• Unicode letters are allowed but discouraged for interop. They are the letters of the Basic Multilingual Plane — C#'s identifier alphabet (Axiom 1): été is an identifier, while a letter outside the BMP, such as 𝒳 (U+1D4B3), is refused with SPY0015 although Python accepts it (deviation identifier-letters-bmp-only in docs/deviations.yaml)

Examples

# Valid identifiers
x
my_variable
_private
ClassName
MAX_SIZE
value2
_internal_counter

# Invalid identifiers
2fast      # Cannot start with digit
my-var     # Hyphen not allowed
class      # Keyword

Naming Conventions

See naming_conventions.md for naming conventions of various symbols.

Literal Names (Backtick Escaping)

Any symbol in Sharpy can be surrounded with backticks ` to tell the compiler not to transform the name during resolution. This is equivalent to C#'s @ prefix:

# Prevents case transformation
from foo_bar.`abc` import *

# Using a keyword as an identifier
def `class`():
    pass

# Using exact casing without transformation
def `ExactMethodName`():
    pass

An escaped name is an identifier at every site, including the sites where the bare spelling is a soft keyword (keywords.md): an escaped `_` in a call argument is the variable _, not a partial-application placeholder.

def f(a: int, b: int) -> int:
    return a * 10 + b

def main():
    _ = 3
    g = f(1, `_`)
    print(g)                # 13

Implementation - ✅ Native - Backtick names map to @name in C# when needed, or exact casing is preserved.