From afee5fb82dbf8d2be133a7ef112321b5ff961e2f Mon Sep 17 00:00:00 2001 From: Erin Date: Mon, 7 Jun 2021 00:09:45 +0200 Subject: [PATCH] Added basic parsing - Expressions - If, Functio --- src/ast.rs | 8 +- src/error.rs | 16 +++- src/lexer.rs | 8 +- src/parser.rs | 261 ++++++++++++++++++++++++++++++++++++++++++++++++++ 4 files changed, 286 insertions(+), 7 deletions(-) create mode 100644 src/parser.rs diff --git a/src/ast.rs b/src/ast.rs index a8643171..bbf6d691 100644 --- a/src/ast.rs +++ b/src/ast.rs @@ -5,7 +5,7 @@ //! //! Expressions are just operations and they cannot be //! used as statements. Functions in AbleScript are in fact -//! just plain subroutines and they do not return any value, +//! just plain subroutines and they do not return any value, //! so their calls are statements. use crate::variables::Value; @@ -18,6 +18,12 @@ pub struct Iden { pub span: Span, } +impl Iden { + pub fn new(iden: String, span: Span) -> Self { + Self { iden, span } + } +} + #[derive(Debug)] pub struct Block { pub block: Vec, diff --git a/src/error.rs b/src/error.rs index bd150013..6168f347 100644 --- a/src/error.rs +++ b/src/error.rs @@ -1,6 +1,6 @@ use std::ops::Range; -use crate::brian::InterpretError; +use crate::{brian::InterpretError, lexer::Token}; #[derive(Debug, Clone)] pub struct Error { @@ -11,7 +11,8 @@ pub struct Error { #[derive(Debug, Clone)] pub enum ErrorKind { SyntaxError(String), - EndOfTokenStream, + UnexpectedEof, + UnexpectedToken(Token), InvalidIdentifier, UnknownVariable(String), MeloVariable(String), @@ -19,4 +20,15 @@ pub enum ErrorKind { TopLevelBreak, ArithmeticError, BfInterpretError(InterpretError), + MissingLhs, +} + +impl Error { + pub fn new(kind: ErrorKind, span: Range) -> Self { + Self { kind, span } + } + + pub fn unexpected_eof() -> Self { + Self::new(ErrorKind::UnexpectedEof, 0..0) + } } diff --git a/src/lexer.rs b/src/lexer.rs index b04ff077..2ac317e2 100644 --- a/src/lexer.rs +++ b/src/lexer.rs @@ -6,10 +6,10 @@ use crate::variables::Abool; pub enum Token { // Symbols #[token("(")] - LeftParenthesis, + LeftParen, #[token(")")] - RightParenthesis, + RightParen, #[token("[")] LeftBracket, @@ -184,8 +184,8 @@ mod tests { let expected = &[ Functio, Identifier("test".to_owned()), - LeftParenthesis, - RightParenthesis, + LeftParen, + RightParen, LeftCurly, Variable, Identifier("a".to_owned()), diff --git a/src/parser.rs b/src/parser.rs new file mode 100644 index 00000000..0a51fc79 --- /dev/null +++ b/src/parser.rs @@ -0,0 +1,261 @@ +//! AbleScript Parser +//! +//! Type of this parser is recursive descent + +use logos::{Lexer, Logos}; + +use crate::ast::*; +use crate::error::{Error, ErrorKind}; +use crate::lexer::Token; +use crate::variables::Value; + +/// Parser structure which holds lexer and metadata +/// +/// Make one using [`Parser::new`] function +pub struct Parser<'source> { + lexer: Lexer<'source, Token>, +} + +impl<'source> Parser<'source> { + /// Create a new parser from source code + pub fn new(source: &'source str) -> Self { + Self { + lexer: Token::lexer(source), + } + } + + /// Start parsing tokens + /// + /// Loops trough lexer, parses statements, returns AST + pub fn init(&mut self) -> Result, Error> { + let mut ast = vec![]; + while let Some(token) = self.lexer.next() { + ast.push(self.parse(token)?); + } + Ok(ast) + } + + /// Parse a token + /// + /// This function will route to corresponding flow functions + /// which may advance the lexer iterator + fn parse(&mut self, token: Token) -> Result { + let start = self.lexer.span().start; + + match token { + Token::If => Ok(Stmt::new(self.if_flow()?, start..self.lexer.span().end)), + Token::Functio => Ok(Stmt::new( + self.functio_flow()?, + start..self.lexer.span().end, + )), + t => Err(Error { + kind: ErrorKind::UnexpectedToken(t), + span: start..self.lexer.span().end, + }), + } + } + + /// Require next item to be equal with expected one + fn require(&mut self, expected: Token) -> Result<(), Error> { + match self.lexer.next() { + Some(t) if t == expected => Ok(()), + Some(t) => Err(Error::new(ErrorKind::UnexpectedToken(t), self.lexer.span())), + None => Err(Error::unexpected_eof()), + } + } + + /// Get an Identifier + fn get_iden(&mut self) -> Result { + match self.lexer.next().ok_or(Error::unexpected_eof())? { + Token::Identifier(iden) => Ok(Iden { + iden, + span: self.lexer.span(), + }), + t => Err(Error::new(ErrorKind::UnexpectedToken(t), self.lexer.span())), + } + } + + /// Parse an expression + /// + /// AbleScript strongly separates expressions from statements. + /// Expressions do not have any side effects and the are + /// only mathematial and logical operations or values. + fn parse_expr(&mut self, token: Token, buf: &mut Option) -> Result { + let start = self.lexer.span().start; + + match token { + // Values + Token::Identifier(i) => Ok(Expr::new( + ExprKind::Variable(i), + start..self.lexer.span().end, + )), + Token::Abool(a) => Ok(Expr::new( + ExprKind::Literal(Value::Abool(a)), + start..self.lexer.span().end, + )), + Token::Bool(b) => Ok(Expr::new( + ExprKind::Literal(Value::Bool(b)), + start..self.lexer.span().end, + )), + Token::Integer(i) => Ok(Expr::new( + ExprKind::Literal(Value::Int(i)), + start..self.lexer.span().end, + )), + Token::String(s) => Ok(Expr::new( + ExprKind::Literal(Value::Str(s)), + start..self.lexer.span().end, + )), + Token::Nul => Ok(Expr::new( + ExprKind::Literal(Value::Nul), + start..self.lexer.span().end, + )), + + // Operations + Token::Plus => Ok(Expr::new( + self.op_flow(BinOpKind::Add, buf)?, + start..self.lexer.span().end, + )), + Token::Minus => Ok(Expr::new( + self.op_flow(BinOpKind::Subtract, buf)?, + start..self.lexer.span().end, + )), + Token::Star => Ok(Expr::new( + self.op_flow(BinOpKind::Multiply, buf)?, + start..self.lexer.span().end, + )), + Token::FwdSlash => Ok(Expr::new( + self.op_flow(BinOpKind::Divide, buf)?, + start..self.lexer.span().end, + )), + Token::EqualEqual => Ok(Expr::new( + self.op_flow(BinOpKind::Equal, buf)?, + start..self.lexer.span().end, + )), + Token::NotEqual => Ok(Expr::new( + self.op_flow(BinOpKind::NotEqual, buf)?, + start..self.lexer.span().end, + )), + Token::And => Ok(Expr::new( + self.op_flow(BinOpKind::And, buf)?, + start..self.lexer.span().end, + )), + Token::Or => Ok(Expr::new( + self.op_flow(BinOpKind::Or, buf)?, + start..self.lexer.span().end, + )), + Token::LessThan => Ok(Expr::new( + self.op_flow(BinOpKind::Less, buf)?, + start..self.lexer.span().end, + )), + Token::GreaterThan => Ok(Expr::new( + self.op_flow(BinOpKind::Greater, buf)?, + start..self.lexer.span().end, + )), + + Token::Not => Ok(Expr::new( + { + let next = self.lexer.next().ok_or(Error::unexpected_eof())?; + ExprKind::Not(Box::new(self.parse_expr(next, buf)?)) + }, + start..self.lexer.span().end, + )), + Token::LeftParen => self.expr_flow(Token::RightParen), + t => Err(Error::new( + ErrorKind::UnexpectedToken(t), + start..self.lexer.span().end, + )), + } + } + + /// Flow for operators + /// + /// Generates operation from LHS buffer and next expression as RHS + /// + /// This is unaware of precedence, as AbleScript do not have it + fn op_flow(&mut self, kind: BinOpKind, lhs: &mut Option) -> Result { + Ok(ExprKind::BinOp { + lhs: Box::new( + lhs.take() + .ok_or(Error::new(ErrorKind::MissingLhs, self.lexer.span()))?, + ), + rhs: { + let next = self.lexer.next().ok_or(Error::unexpected_eof())?; + Box::new(self.parse_expr(next, &mut None)?) + }, + kind, + }) + } + + /// Parse expressions until terminate token + fn expr_flow(&mut self, terminate: Token) -> Result { + let mut buf = None; + Ok(loop { + match self.lexer.next().ok_or(Error::unexpected_eof())? { + t if t == terminate => break buf.take().unwrap(), + t => buf = Some(self.parse_expr(t, &mut buf)?), + } + }) + } + + /// Parse a list of statements between curly braces + fn parse_block(&mut self) -> Result { + self.require(Token::LeftCurly)?; + let mut block = vec![]; + + loop { + match self.lexer.next().ok_or(Error::unexpected_eof())? { + Token::RightCurly => break, + t => block.push(self.parse(t)?), + } + } + Ok(Block { block }) + } + + /// Parse If flow + /// + /// Consists of condition and block, there is no else + fn if_flow(&mut self) -> Result { + self.require(Token::LeftParen)?; + + let cond = self.expr_flow(Token::RightParen)?; + + let body = self.parse_block()?; + + Ok(StmtKind::If { cond, body }) + } + + /// Parse functio flow + /// + /// functio $iden (a, b, c) { ... } + fn functio_flow(&mut self) -> Result { + let iden = self.get_iden()?; + + self.require(Token::LeftParen)?; + + let mut args = vec![]; + loop { + match self.lexer.next().ok_or(Error::unexpected_eof())? { + Token::RightParen => break, + Token::Identifier(i) => { + args.push(Iden::new(i, self.lexer.span())); + + match self.lexer.next().ok_or(Error::unexpected_eof())? { + Token::Comma => continue, + Token::RightParen => break, + t => { + return Err(Error::new( + ErrorKind::UnexpectedToken(t), + self.lexer.span(), + )) + } + } + } + t => return Err(Error::new(ErrorKind::UnexpectedToken(t), self.lexer.span())), + } + } + + let body = self.parse_block()?; + + Ok(StmtKind::Functio { iden, args, body }) + } +}