283 lines
10 KiB
Python
283 lines
10 KiB
Python
from typing import Optional
|
|
|
|
from core.ast.midas import (
|
|
BinaryExpr,
|
|
ComplexTypeStmt,
|
|
Expr,
|
|
ExtendStmt,
|
|
GetExpr,
|
|
GroupingExpr,
|
|
LiteralExpr,
|
|
LogicalExpr,
|
|
OpStmt,
|
|
PredicateStmt,
|
|
PropertyStmt,
|
|
SimpleTypeExpr,
|
|
SimpleTypeStmt,
|
|
Stmt,
|
|
TemplateExpr,
|
|
TypeExpr,
|
|
UnaryExpr,
|
|
VariableExpr,
|
|
WildcardExpr,
|
|
)
|
|
from lexer.token import Token, TokenType
|
|
from parser.base import Parser
|
|
from parser.errors import ParsingError
|
|
|
|
|
|
class MidasParser(Parser):
|
|
"""A simple parser for midas type definitions"""
|
|
|
|
SYNC_BOUNDARY: set[TokenType] = {
|
|
TokenType.TYPE,
|
|
TokenType.OP,
|
|
TokenType.EXTEND,
|
|
TokenType.PREDICATE,
|
|
}
|
|
|
|
def parse(self) -> list[Stmt]:
|
|
statements: list[Stmt] = []
|
|
while not self.is_at_end():
|
|
stmt: Optional[Stmt] = self.declaration()
|
|
if stmt is None:
|
|
print("Early stop")
|
|
break
|
|
statements.append(stmt)
|
|
return statements
|
|
|
|
def synchronize(self):
|
|
"""Skip tokens until a synchronization boundary is found
|
|
|
|
This method allows gracefully recovering from a parse error
|
|
to a safe place and continue parsing
|
|
"""
|
|
self.advance()
|
|
while not self.is_at_end():
|
|
if self.previous().type == TokenType.NEWLINE:
|
|
return
|
|
if self.peek().type in self.SYNC_BOUNDARY:
|
|
return
|
|
self.advance()
|
|
|
|
def declaration(self) -> Optional[Stmt]:
|
|
"""Try and parse a declaration
|
|
|
|
Any parsing error is caught and None is returned
|
|
|
|
Returns:
|
|
Optional[Stmt]: the parsed Midas statement, or None if a ParsingError was raised
|
|
"""
|
|
try:
|
|
if self.match(TokenType.TYPE):
|
|
return self.type_declaration()
|
|
if self.match(TokenType.EXTEND):
|
|
return self.extend_declaration()
|
|
if self.match(TokenType.PREDICATE):
|
|
return self.predicate_declaration()
|
|
raise self.error(self.peek(), "Unexpected token")
|
|
except ParsingError:
|
|
self.synchronize()
|
|
return None
|
|
|
|
def type_declaration(self) -> SimpleTypeStmt | ComplexTypeStmt:
|
|
"""Parse a type declaration
|
|
|
|
A type declaration is written `type Name<TypeExpr, ...>` optionally followed by a brace-wrapped body
|
|
|
|
Returns:
|
|
TypeStmt: the parsed type declaration statement
|
|
"""
|
|
name: Token = self.consume(TokenType.IDENTIFIER, "Expected type name")
|
|
template: Optional[TemplateExpr] = None
|
|
if self.check(TokenType.LEFT_BRACKET):
|
|
template = self.template_expr()
|
|
|
|
if self.match(TokenType.LEFT_PAREN):
|
|
base: TypeExpr = self.type_expr()
|
|
self.consume(TokenType.RIGHT_PAREN, "Unclosed base type parenthesis")
|
|
constraint: Optional[Expr] = None
|
|
if self.match(TokenType.WHERE):
|
|
constraint = self.constraint()
|
|
return SimpleTypeStmt(
|
|
name=name, template=template, base=base, constraint=constraint
|
|
)
|
|
else:
|
|
properties: list[PropertyStmt] = self.type_properties()
|
|
return ComplexTypeStmt(name=name, template=template, properties=properties)
|
|
|
|
def template_expr(self) -> TemplateExpr:
|
|
self.consume(TokenType.LEFT_BRACKET, "Missing '[' before template expression")
|
|
type: TypeExpr = self.type_expr()
|
|
self.consume(TokenType.RIGHT_BRACKET, "Missing ']' after template expression")
|
|
return TemplateExpr(type=type)
|
|
|
|
def type_expr(self) -> TypeExpr:
|
|
"""Parse a type expression
|
|
|
|
Returns:
|
|
TypeExpr: the parsed type expression
|
|
"""
|
|
name: Token = self.consume(TokenType.IDENTIFIER, "Expected type name")
|
|
template: Optional[TemplateExpr] = None
|
|
if self.check(TokenType.LEFT_BRACKET):
|
|
template = self.template_expr()
|
|
optional: bool = self.match(TokenType.QMARK)
|
|
return TypeExpr(name=name, template=template, optional=optional)
|
|
|
|
def simple_type_expr(self) -> SimpleTypeExpr:
|
|
name: Token = self.consume(TokenType.IDENTIFIER, "Expected type name")
|
|
optional: bool = self.match(TokenType.QMARK)
|
|
return SimpleTypeExpr(name=name, optional=optional)
|
|
|
|
def constraint(self) -> Expr:
|
|
return self.and_()
|
|
|
|
def and_(self) -> Expr:
|
|
expr: Expr = self.equality()
|
|
while self.match(TokenType.AND):
|
|
operator: Token = self.previous()
|
|
right: Expr = self.equality()
|
|
expr = LogicalExpr(left=expr, operator=operator, right=right)
|
|
return expr
|
|
|
|
def equality(self) -> Expr:
|
|
expr: Expr = self.comparison()
|
|
while self.match(TokenType.BANG_EQUAL, TokenType.EQUAL_EQUAL):
|
|
operator: Token = self.previous()
|
|
right: Expr = self.comparison()
|
|
expr = BinaryExpr(left=expr, operator=operator, right=right)
|
|
return expr
|
|
|
|
def comparison(self) -> Expr:
|
|
expr: Expr = self.unary()
|
|
while self.match(
|
|
TokenType.LESS,
|
|
TokenType.LESS_EQUAL,
|
|
TokenType.GREATER,
|
|
TokenType.GREATER_EQUAL,
|
|
):
|
|
operator: Token = self.previous()
|
|
right: Expr = self.unary()
|
|
expr = BinaryExpr(left=expr, operator=operator, right=right)
|
|
return expr
|
|
|
|
def unary(self) -> Expr:
|
|
if self.match(TokenType.MINUS):
|
|
operator: Token = self.previous()
|
|
right: Expr = self.unary()
|
|
return UnaryExpr(operator=operator, right=right)
|
|
return self.reference()
|
|
|
|
def reference(self) -> Expr:
|
|
expr: Expr = self.primary()
|
|
while self.match(TokenType.DOT):
|
|
name: Token = self.consume(
|
|
TokenType.IDENTIFIER, "Expected property name after '.'"
|
|
)
|
|
expr = GetExpr(expr=expr, name=name)
|
|
return expr
|
|
|
|
def primary(self) -> Expr:
|
|
if self.match(TokenType.FALSE):
|
|
return LiteralExpr(False)
|
|
if self.match(TokenType.TRUE):
|
|
return LiteralExpr(True)
|
|
if self.match(TokenType.NONE):
|
|
return LiteralExpr(None)
|
|
|
|
if self.match(TokenType.NUMBER):
|
|
return LiteralExpr(self.previous().value)
|
|
|
|
if self.match(TokenType.IDENTIFIER):
|
|
return VariableExpr(self.previous())
|
|
|
|
if self.match(TokenType.UNDERSCORE):
|
|
return WildcardExpr(self.previous())
|
|
|
|
if self.match(TokenType.LEFT_PAREN):
|
|
expr: Expr = self.constraint()
|
|
self.consume(TokenType.RIGHT_PAREN, "Unclosed parenthesis")
|
|
return GroupingExpr(expr)
|
|
|
|
raise self.error(self.peek(), "Expected expression")
|
|
|
|
def type_properties(self) -> list[PropertyStmt]:
|
|
"""Parse a type definition body
|
|
|
|
A type definition body is a set of whitespace-separated
|
|
property statements enclosed in curly braces
|
|
|
|
Returns:
|
|
TypeBodyStmt: the parsed type body expression
|
|
"""
|
|
self.consume(TokenType.LEFT_BRACE, "Expected '{' to start type body")
|
|
properties: list[PropertyStmt] = []
|
|
while not self.check(TokenType.RIGHT_BRACE) and not self.is_at_end():
|
|
properties.append(self.property_stmt())
|
|
self.consume(TokenType.RIGHT_BRACE, "Unclosed type body")
|
|
return properties
|
|
|
|
def property_stmt(self) -> PropertyStmt:
|
|
"""Parse a property statement
|
|
|
|
A type property statement is written `name: Type`
|
|
|
|
Returns:
|
|
PropertyStmt: the parsed property statement
|
|
"""
|
|
name: Token = self.consume(TokenType.IDENTIFIER, "Expected property name")
|
|
self.consume(TokenType.COLON, "Expected ':' after property name")
|
|
type: TypeExpr = self.type_expr()
|
|
constraint: Optional[Expr] = None
|
|
if self.match(TokenType.WHERE):
|
|
constraint = self.constraint()
|
|
return PropertyStmt(name=name, type=type, constraint=constraint)
|
|
|
|
def extend_declaration(self) -> ExtendStmt:
|
|
type: TypeExpr = self.type_expr()
|
|
self.consume(TokenType.LEFT_BRACE, "Expected '{' to start extend body")
|
|
operations: list[OpStmt] = []
|
|
while not self.is_at_end() and not self.check(TokenType.RIGHT_BRACE):
|
|
operations.append(self.op_declaration())
|
|
self.consume(TokenType.RIGHT_BRACE, "Unclosed extend body")
|
|
return ExtendStmt(type=type, operations=operations)
|
|
|
|
def op_declaration(self) -> OpStmt:
|
|
"""Parse an operation definition
|
|
|
|
An operation is written `op <Type1> operator <Type2> = <Type3>` where `operator` can be any single token
|
|
|
|
Returns:
|
|
OpStmt: the parsed operation statement
|
|
"""
|
|
self.consume(TokenType.OP, "Expected 'op' keyword")
|
|
|
|
name: Token = self.consume(TokenType.IDENTIFIER, "Expected operation name")
|
|
self.consume(TokenType.LEFT_PAREN, "Expected '(' before operand type")
|
|
operand: TypeExpr = self.type_expr()
|
|
self.consume(TokenType.RIGHT_PAREN, "Expected ')' after operand type")
|
|
|
|
self.consume(TokenType.ARROW, "Expected '->' before result type")
|
|
result: TypeExpr = self.type_expr()
|
|
|
|
return OpStmt(name=name, operand=operand, result=result)
|
|
|
|
def predicate_declaration(self) -> PredicateStmt:
|
|
"""Parse a type constraint declaration
|
|
|
|
A constraint is written `constraint Name = constraint_expression`
|
|
|
|
Returns:
|
|
ConstraintStmt: the parsed constraint declaration statement
|
|
"""
|
|
name: Token = self.consume(TokenType.IDENTIFIER, "Expected predicate name")
|
|
self.consume(TokenType.LEFT_PAREN, "Expected '(' before predicate subject")
|
|
subject: Token = self.consume(TokenType.IDENTIFIER, "Expected subject name")
|
|
self.consume(TokenType.COLON, "Expected ':' after subject name")
|
|
type: TypeExpr = self.type_expr()
|
|
self.consume(TokenType.RIGHT_PAREN, "Expected ')' after predicate subject")
|
|
self.consume(TokenType.EQUAL, "Expected '=' after predicate subject")
|
|
condition: Expr = self.constraint()
|
|
return PredicateStmt(name=name, subject=subject, type=type, condition=condition)
|