From 8915cd6fba9a7d449efc13543d7d0db4fca9d0d5 Mon Sep 17 00:00:00 2001
From: Vincent Ambo <mail@tazj.in>
Date: Thu, 31 Dec 2020 18:05:58 +0300
Subject: [PATCH] feat(tazjin/rlox): Implement block parsing

Change-Id: I1b7235ed71fa36120984a36f22cd564f59581352
Reviewed-on: https://cl.tvl.fyi/c/depot/+/2303
Reviewed-by: tazjin <mail@tazj.in>
Tested-by: BuildkiteCI
---
 users/tazjin/rlox/src/errors.rs      |  1 +
 users/tazjin/rlox/src/interpreter.rs |  5 +++--
 users/tazjin/rlox/src/parser.rs      | 23 +++++++++++++++++++----
 3 files changed, 23 insertions(+), 6 deletions(-)

diff --git a/users/tazjin/rlox/src/errors.rs b/users/tazjin/rlox/src/errors.rs
index 162b80dc0..10fc0a352 100644
--- a/users/tazjin/rlox/src/errors.rs
+++ b/users/tazjin/rlox/src/errors.rs
@@ -5,6 +5,7 @@ pub enum ErrorKind {
     UnmatchedParens,
     ExpectedExpression(String),
     ExpectedSemicolon,
+    ExpectedClosingBrace,
     ExpectedVariableName,
     TypeError(String),
     UndefinedVariable(String),
diff --git a/users/tazjin/rlox/src/interpreter.rs b/users/tazjin/rlox/src/interpreter.rs
index edaa5e28f..ba66faf79 100644
--- a/users/tazjin/rlox/src/interpreter.rs
+++ b/users/tazjin/rlox/src/interpreter.rs
@@ -1,5 +1,5 @@
 use crate::errors::{Error, ErrorKind};
-use crate::parser::{self, Expr, Literal, Program, Statement};
+use crate::parser::{self, Block, Expr, Literal, Statement};
 use crate::scanner::{self, TokenKind};
 use std::collections::HashMap;
 use std::rc::Rc;
@@ -78,7 +78,7 @@ pub struct Interpreter {
 }
 
 impl Interpreter {
-    pub fn interpret<'a>(&mut self, program: &Program<'a>) -> Result<(), Error> {
+    pub fn interpret<'a>(&mut self, program: &Block<'a>) -> Result<(), Error> {
         for stmt in program {
             self.interpret_stmt(stmt)?;
         }
@@ -96,6 +96,7 @@ impl Interpreter {
                 println!("{:?}", result)
             }
             Statement::Var(var) => return self.interpret_var(var),
+            Statement::Block(_) => unimplemented!(),
         }
 
         Ok(())
diff --git a/users/tazjin/rlox/src/parser.rs b/users/tazjin/rlox/src/parser.rs
index 1a271fd0a..94ad2f4c4 100644
--- a/users/tazjin/rlox/src/parser.rs
+++ b/users/tazjin/rlox/src/parser.rs
@@ -62,15 +62,16 @@ pub struct Var<'a> {
     pub initialiser: Option<Expr<'a>>,
 }
 
+pub type Block<'a> = Vec<Statement<'a>>;
+
 #[derive(Debug)]
 pub enum Statement<'a> {
     Expr(Expr<'a>),
     Print(Expr<'a>),
     Var(Var<'a>),
+    Block(Block<'a>),
 }
 
-pub type Program<'a> = Vec<Statement<'a>>;
-
 // Parser
 
 /*
@@ -143,6 +144,8 @@ impl<'a> Parser<'a> {
     fn statement(&mut self) -> StmtResult<'a> {
         if self.match_token(&[TokenKind::Print]) {
             self.print_statement()
+        } else if self.match_token(&[TokenKind::LeftBrace]) {
+            self.block_statement()
         } else {
             self.expr_statement()
         }
@@ -154,6 +157,18 @@ impl<'a> Parser<'a> {
         Ok(Statement::Print(expr))
     }
 
+    fn block_statement(&mut self) -> StmtResult<'a> {
+        let mut block: Block<'a> = vec![];
+
+        while !self.check_token(&TokenKind::RightBrace) && !self.is_at_end() {
+            block.push(self.declaration()?);
+        }
+
+        self.consume(&TokenKind::RightBrace, ErrorKind::ExpectedClosingBrace)?;
+
+        Ok(Statement::Block(block))
+    }
+
     fn expr_statement(&mut self) -> StmtResult<'a> {
         let expr = self.expression()?;
         self.consume(&TokenKind::Semicolon, ErrorKind::ExpectedSemicolon)?;
@@ -349,9 +364,9 @@ impl<'a> Parser<'a> {
     }
 }
 
-pub fn parse<'a>(tokens: Vec<Token<'a>>) -> Result<Program<'a>, Vec<Error>> {
+pub fn parse<'a>(tokens: Vec<Token<'a>>) -> Result<Block<'a>, Vec<Error>> {
     let mut parser = Parser { tokens, current: 0 };
-    let mut program: Program<'a> = vec![];
+    let mut program: Block<'a> = vec![];
     let mut errors: Vec<Error> = vec![];
 
     while !parser.is_at_end() {