add assignments

grammar.txt

@@ -13,13 +13,13 @@
               | <break-stmt>
               | <return-stmt>
               | <block>
-              | <expression-statement>
 
 
 <declaration> ::= "let" <IDENT> "=" <expression> ";"
 
 
 <assignment> ::= { call "." } <IDENT> "=" <expression> ";"
+               | <expression> ";"
 
 
 <fn-decl> ::= "fn" <IDENT> <fn-args> <block>

src/parse/mod.rs

@@ -75,9 +75,8 @@ impl<'code> Parser<'code> {
             TokenType::Return => self.return_stmt(),
             TokenType::BraceO => Ok(Stmt::Block(self.block()?)),
             _ => {
-                let expr = self.expression()?;
-                self.expect(TokenType::Semi)?;
-                Ok(Stmt::Expr(expr))
+                let stmt = self.assignment()?;
+                Ok(stmt)
             }
         }
     }
@@ -95,10 +94,6 @@ impl<'code> Parser<'code> {
         }))
     }
 
-    fn assignment(&mut self) -> ParseResult<'code, Stmt> {
-        todo!("oh god no")
-    }
-
     fn fn_decl(&mut self) -> ParseResult<'code, Stmt> {
         let keyword_span = self.expect(TokenType::Fn)?.span;
         let name = self.ident()?;
@@ -215,6 +210,24 @@ impl<'code> Parser<'code> {
         }
     }
 
+    fn assignment(&mut self) -> ParseResult<'code, Stmt> {
+        let expr = self.expression()?;
+
+        if let Some(TokenType::Equal) = self.peek_kind() {
+            let _ = self.expect(TokenType::Equal)?;
+            let init = self.expression()?;
+            let semi_span = self.expect(TokenType::Semi)?.span;
+            Ok(Stmt::Assignment(Assignment {
+                span: expr.span().extend(semi_span),
+                lhs: expr,
+                rhs: init,
+            }))
+        } else {
+            let _ = self.expect(TokenType::Semi)?;
+            Ok(Stmt::Expr(expr))
+        }
+    }
+
     fn expression(&mut self) -> ParseResult<'code, Expr> {
         self.logical_or()
     }

src/parse/test.rs

@@ -73,6 +73,63 @@ fn test_number_literal<F: FnOnce(Vec<Token<'_>>) -> Expr>(parser: F) {
     assert_eq!(num_lit(10.0), unary);
 }
 
+mod assignment {
+    use super::prelude::*;
+
+    fn parse_assignment(tokens: Vec<Token>) -> Stmt {
+        let mut parser = parser(tokens);
+        parser.assignment().unwrap()
+    }
+
+    #[test]
+    fn simple() {
+        let tokens = [Ident("hugo"), Equal, Number(10.0), Semi].map(token).into();
+        let ast = parse_assignment(tokens);
+        assert_eq!(
+            Stmt::Assignment(Assignment {
+                span: Default::default(),
+                lhs: Expr::Ident(ident("hugo")),
+                rhs: num_lit(10.0)
+            }),
+            ast
+        );
+    }
+
+    #[test]
+    fn call_expr() {
+        let tokens = [
+            Ident("hugo"),
+            Dot,
+            Ident("age"),
+            Equal,
+            Number(2021.0),
+            Minus,
+            Number(1986.0),
+            Semi,
+        ]
+        .map(token)
+        .into();
+        let ast = parse_assignment(tokens);
+        assert_eq!(
+            Stmt::Assignment(Assignment {
+                span: Default::default(),
+                lhs: Expr::Call(Box::new(Call {
+                    callee: Expr::Ident(ident("hugo")),
+                    span: Default::default(),
+                    kind: CallKind::Field(ident("age"))
+                })),
+                rhs: Expr::BinaryOp(Box::new(BinaryOp {
+                    span: Default::default(),
+                    lhs: num_lit(2021.0),
+                    rhs: num_lit(1986.0),
+                    kind: BinaryOpKind::Sub
+                }))
+            }),
+            ast
+        );
+    }
+}
+
 mod r#fn {
     use super::prelude::*;