feat(parser): add documentation to Midas parser

parser/midas.py

@@ -16,6 +16,8 @@ from parser.errors import ParsingError
 
 
 class MidasParser(Parser):
+    """A simple parser for midas type definitions"""
+
     SYNC_BOUNDARY: set[TokenType] = {TokenType.TYPE, TokenType.OP, TokenType.CONSTRAINT}
 
     def parse(self) -> list[Stmt]:
@@ -29,6 +31,11 @@ class MidasParser(Parser):
         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:
@@ -38,6 +45,13 @@ class MidasParser(Parser):
             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()
@@ -50,6 +64,13 @@ class MidasParser(Parser):
             return None
 
     def type_declaration(self) -> TypeStmt:
+        """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")
         self.consume(TokenType.LESS, "Expected '<' after type name")
         bases: list[TypeExpr] = []
@@ -66,6 +87,11 @@ class MidasParser(Parser):
         return TypeStmt(name=name, bases=bases, body=body)
 
     def type_expr(self) -> TypeExpr:
+        """Parse a type expression
+
+        Returns:
+            TypeExpr: the parsed type expression
+        """
         name: Token = self.consume(TokenType.IDENTIFIER, "Expected type name")
         constraints: list[ConstraintExpr] = []
 
@@ -75,10 +101,23 @@ class MidasParser(Parser):
         return TypeExpr(name=name, constraints=constraints)
 
     def constraint_expr(self) -> ConstraintExpr:
+        """Parse a type constraint
+
+        Returns:
+            ConstraintExpr: the parsed type constraint expression
+        """
         # TODO
         return ConstraintExpr()
 
     def type_body_expr(self) -> TypeBodyExpr:
+        """Parse a type definition body
+
+        A type definition body is a set of whitespace-separated
+        property statements enclosed in curly braces
+
+        Returns:
+            TypeBodyExpr: 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():
@@ -87,12 +126,26 @@ class MidasParser(Parser):
         return TypeBodyExpr(properties=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()
         return PropertyStmt(name=name, type=type)
 
     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.LESS, "Expected '<' before first type")
         left: TypeExpr = self.type_expr()
         self.consume(TokenType.GREATER, "Expected '>' after first type")
@@ -112,6 +165,13 @@ class MidasParser(Parser):
         return OpStmt(left=left, op=op, right=right, result=result)
 
     def constraint_declaration(self) -> ConstraintStmt:
+        """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 constraint name")
         self.consume(TokenType.EQUAL, "Expected '=' after constraint name")
         constraint: ConstraintExpr = self.constraint_expr()