feat(tazjin/rlox): Parse & interpret while statements r/2062

Change-Id: Iee772274de95dfd6a6d4af973402859aeda17b1d
Reviewed-on: https://cl.tvl.fyi/c/depot/+/2325
Reviewed-by: tazjin <mail@tazj.in>
Tested-by: BuildkiteCI

1 files changed, 31 insertions, 0 deletions

diff --git a/users/tazjin/rlox/src/parser.rs b/users/tazjin/rlox/src/parser.rs
index ac99f19cb2ee..62296ca02c3b 100644
--- a/users/tazjin/rlox/src/parser.rs
+++ b/users/tazjin/rlox/src/parser.rs
@@ -77,6 +77,12 @@ pub struct If<'a> {
     pub else_branch: Option<Box<Statement<'a>>>,
 }
 
+#[derive(Debug)]
+pub struct While<'a> {
+    pub condition: Expr<'a>,
+    pub body: Box<Statement<'a>>,
+}
+
 pub type Block<'a> = Vec<Statement<'a>>;
 
 #[derive(Debug)]
@@ -86,6 +92,7 @@ pub enum Statement<'a> {
     Var(Var<'a>),
     Block(Block<'a>),
     If(If<'a>),
+    While(While<'a>),
 }
 
 // Parser
@@ -99,8 +106,11 @@ declaration    → varDecl
 statement      → exprStmt
                | ifStmt
                | printStmt
+               | whileStmt
                | block ;
 
+whileStmt      → "while" "(" expression ")" statement ;
+
 exprStmt       → expression ";" ;
 
 ifStmt         → "if" "(" expression ")" statement
@@ -172,6 +182,8 @@ impl<'a> Parser<'a> {
             self.block_statement()
         } else if self.match_token(&[TokenKind::If]) {
             self.if_statement()
+        } else if self.match_token(&[TokenKind::While]) {
+            self.while_statement()
         } else {
             self.expr_statement()
         }
@@ -221,6 +233,25 @@ impl<'a> Parser<'a> {
         Ok(Statement::If(stmt))
     }
 
+    fn while_statement(&mut self) -> StmtResult<'a> {
+        self.consume(
+            &TokenKind::LeftParen,
+            ErrorKind::ExpectedToken("Expected '(' after 'while'"),
+        )?;
+
+        let condition = self.expression()?;
+
+        self.consume(
+            &TokenKind::RightParen,
+            ErrorKind::ExpectedToken("Expected ')' after 'while'"),
+        )?;
+
+        Ok(Statement::While(While {
+            condition,
+            body: Box::new(self.statement()?),
+        }))
+    }
+
     fn expr_statement(&mut self) -> StmtResult<'a> {
         let expr = self.expression()?;
         self.consume(&TokenKind::Semicolon, ErrorKind::ExpectedSemicolon)?;