def visit_this_expr(self, expr):
if self.current_class == ClassType.NONE:
Error.error(expr.keyword, "Cannot use 'this' outside of a class.")
return None
self.resolve_local(expr, expr.keyword)
return None
def visit_class_stmt(self, stmt):
enclosing_class = self.current_class
self.current_class = ClassType.CLASS
self.declare(stmt.name)
self.define(stmt.name)
if stmt.superclass is not None:
if stmt.name.lexem == stmt.superclass.name.lexem:
Error.error(stmt.superclass.name,
"A class cannot inherit from itself.")
else:
self.current_class = ClassType.SUBCLASS
self.resolve(stmt.superclass)
self.begin_scope()
self.scopes[-1]["super"] = True
self.begin_scope()
self.scopes[-1]["this"] = True
for method in stmt.methods:
declaration = Function.method
if method.name.lexem == "init":
declaration = Function.initializer
self.resolve_function(method, declaration)
self.end_scope()
if stmt.superclass is not None:
self.end_scope()
self.current_class = enclosing_class
return None
def interpret(self, statements):
try:
for statement in statements:
if statement is not None:
self.execute(statement)
except RuntimeException as error:
Error.runtime_error(error)
def visit_variable_expr(self, expr):
if not len(self.scopes) == 0 and self.scopes[-1].keys().__contains__(expr.name.lexem) and \
not self.scopes[-1][expr.name.lexem]:
Error.error(expr.name,
"Cannot read local variable in its own initializer.")
self.resolve_local(expr, expr.name)
return None
def visit_super_expr(self, expr):
if self.current_class == ClassType.NONE:
Error.error(expr.keyword, "Cannot use 'super' outside of a class.")
elif self.current_class != ClassType.SUBCLASS:
Error.error(
expr.keyword,
"Cannot use 'super' in a class without a super class.")
self.resolve_local(expr, expr.keyword)
return None
def visit_return_stmt(self, stmt):
if self.current_function == Function.none:
Error.error(stmt.keyword, "Cannot return from top-level code")
if stmt.value is not None:
if self.current_function == Function.initializer:
Error.error(stmt.keyword, "Cannot return from an initializer.")
self.resolve(stmt.value)
return None
def scan_token(self):
c = self.advance()
if c == '(':
self.add_token(TokenType.LEFT_PAREN)
elif c == ')':
self.add_token(TokenType.RIGHT_PAREN)
elif c == '{':
self.add_token(TokenType.LEFT_BRACE)
elif c == '}':
self.add_token(TokenType.RIGHT_BRACE)
elif c == ',':
self.add_token(TokenType.COMMA)
elif c == '.':
self.add_token(TokenType.DOT)
elif c == '-':
self.add_token(TokenType.MINUS)
elif c == '%':
self.add_token(TokenType.MODULO)
elif c == '+':
self.add_token(TokenType.PLUS)
elif c == ';':
self.add_token(TokenType.SEMICOLON)
elif c == '*':
self.add_token(TokenType.STAR)
elif c == '!':
self.add_token(
TokenType.BANG_EQUAL if self.match('=') else TokenType.BANG)
elif c == '=':
self.add_token(
TokenType.EQUAL_EQUAL if self.match('=') else TokenType.EQUAL)
elif c == '<':
self.add_token(
TokenType.LESS_EQUAL if self.match('=') else TokenType.LESS)
elif c == '>':
self.add_token(TokenType.GREATER_EQUAL if self.
match('=') else TokenType.GREATER)
elif c == '/':
if self.match('/'):
while (not self.peek() == '\n') and not self.is_at_end():
self.advance()
else:
self.add_token(TokenType.SLASH)
elif c == ' ' or c == '\r' or c == '\t':
return
elif c == '"':
self.string()
elif c == '\n':
self.line += 1
else:
if c.isdigit():
self.number()
elif c.isalpha() or c == '_':
self.identifier()
else:
Error.error(self.line, "Unexpected character.")
def declare(self, name):
if len(self.scopes) == 0:
return
scope = self.scopes[-1]
if scope.keys().__contains__(name.lexem):
Error.error(
name,
"Variable with this name already declared in this scope.")
scope[name.lexem] = False
def string(self):
while not self.peek() == '"' and not self.is_at_end():
if self.peek() == '\n':
self.line += 1
self.advance()
if self.is_at_end():
Error.error(self.line, "Unterminated string.")
return
self.advance()
value = self.source[self.start + 1:self.current - 1]
self.add_token(TokenType.STRING, value)
def error(token, message):
Error.error(token, message)
raise ParseError()