Add compound arithmetic assignment operators

Close #5.

src/ast.rs

@@ -146,6 +146,7 @@ pub struct IfThenStmt {
 #[derive(Debug, Clone)]
 pub enum Stmt {
     Assign(LhsExprNode, ExprNode),
+    AssignOp(LhsExprNode, BinOp, ExprNode),
     VarDecl(Variable, ExprNode),
     Expr(ExprNode),
     Block(Vec<StmtNode>),

src/ast_walk_interpreter.rs

@@ -68,6 +68,9 @@ impl AstWalkInterpreter {
         match s.data {
             Stmt::VarDecl(ref variable, ref expr) => self.eval_stmt_var_decl(variable, expr),
             Stmt::Assign(ref lhs_expr, ref expr) => self.eval_stmt_assign(lhs_expr, expr),
+            Stmt::AssignOp(ref lhs_expr, ref op, ref expr) => {
+                self.eval_stmt_assign_with_op(lhs_expr, op, expr, s)
+            }
             Stmt::Block(ref statements) => self.eval_stmt_block(statements),
             Stmt::Expr(ref expr) => {
                 let val = self.eval_expr(expr)?;
@@ -149,6 +152,42 @@ impl AstWalkInterpreter {
         Ok(StmtResult::None)
     }
 
+    fn eval_stmt_assign_with_op(&mut self,
+                                lhs_expr: &LhsExprNode,
+                                op: &BinOp,
+                                expr: &ExprNode,
+                                stmt: &StmtNode)
+                                -> Result<StmtResult, RuntimeErrorWithPosition> {
+        let val = self.eval_expr_as_value(expr)?;
+        match lhs_expr.data {
+            LhsExpr::Identifier(ref id) => {
+                let prev_expr_val = match self.env.borrow_mut().get_value(id) {
+                    Some(v) => v,
+                    None => {
+                        return Err((RuntimeError::ReferenceError(id.to_owned()), lhs_expr.pos));
+                    }
+                };
+                let retval = match *op {
+                    BinOp::Add => operations::add(prev_expr_val, val),
+                    BinOp::Sub => operations::subtract(prev_expr_val, val),
+                    BinOp::Mul => operations::multiply(prev_expr_val, val),
+                    BinOp::Div => operations::divide(prev_expr_val, val),
+                    BinOp::Mod => operations::modulo(prev_expr_val, val),
+                    BinOp::Lt | BinOp::Lte | BinOp::Gt | BinOp::Gte | BinOp::Eq => unreachable!(),
+                };
+                let new_val = match retval {
+                    Ok(val) => val,
+                    Err(e) => {
+                        return Err((e, stmt.pos));
+                    }
+                };
+                // id must exist, because it was checked above
+                self.env.borrow_mut().set(id, new_val);
+            }
+        };
+        Ok(StmtResult::None)
+    }
+
     fn eval_stmt_block(&mut self,
                        statements: &[StmtNode])
                        -> Result<StmtResult, RuntimeErrorWithPosition> {

src/grammar.rustpeg

@@ -26,6 +26,16 @@ assignment_statement -> Stmt
     = lpos:#position i:identifier rpos:#position __ EQUALS __ e:expr_node __ TERMINATOR {
         Stmt::Assign(LhsExprNode { pos: (lpos, rpos), data: LhsExpr::Identifier(i) }, e)
     }
+    / lpos:#position i:identifier rpos:#position __ op:assign_with_op __ e:expr_node __ TERMINATOR {
+        Stmt::AssignOp(LhsExprNode { pos: (lpos, rpos), data: LhsExpr::Identifier(i) }, op, e)
+    }
+
+assign_with_op -> BinOp
+    = OP_PLUS __ EQUALS { BinOp::Add }
+    / OP_MINUS __ EQUALS { BinOp::Sub }
+    / OP_ASTERISK __ EQUALS { BinOp::Mul }
+    / OP_SLASH __ EQUALS { BinOp::Div }
+    / OP_MOD __ EQUALS { BinOp::Mod }
 
 variable_declaration -> Stmt
     = b:binding_type __ i:identifier __ EQUALS __ e:expr_node __ TERMINATOR {

src/typechecker.rs

@@ -289,6 +289,10 @@ impl TypeChecker {
                 self.check_statement_assignment(lhs_expr, expr);
                 StmtEffect::None
             }
+            Stmt::AssignOp(ref lhs_expr, ref op, ref expr) => {
+                self.check_statement_assignment_with_op(lhs_expr, op, expr, s);
+                StmtEffect::None
+            }
             Stmt::Block(ref statements) => {
                 let current_env = self.env.clone();
                 self.env = TypeEnvironment::create_child(current_env.clone());
@@ -392,6 +396,47 @@ impl TypeChecker {
         };
     }
 
+    fn check_statement_assignment_with_op(&mut self,
+                                          lhs_expr: &LhsExprNode,
+                                          op: &BinOp,
+                                          expr: &ExprNode,
+                                          stmt: &StmtNode) {
+        let checked_type = self.check_expr_as_value(expr);
+        match lhs_expr.data {
+            LhsExpr::Identifier(ref id) => {
+                let prev_type = match self.env.borrow_mut().get_type(id) {
+                    Some(t) => t,
+                    None => {
+                        self.issues
+                            .push((RuntimeError::ReferenceError(id.to_owned()).into(),
+                                   lhs_expr.pos));
+                        Type::Any
+                    }
+                };
+                let retval = match *op {
+                    BinOp::Add => check_add_for_types(&prev_type, &checked_type),
+                    ref op @ BinOp::Sub |
+                    ref op @ BinOp::Mul |
+                    ref op @ BinOp::Div |
+                    ref op @ BinOp::Mod => {
+                        check_binary_arithmetic_for_types(op.clone(), &prev_type, &checked_type)
+                    }
+                    _ => unreachable!(),
+                };
+                let new_type = match retval {
+                    Ok(t) => t,
+                    Err(issue) => {
+                        self.issues.push((issue, stmt.pos));
+                        Type::Any
+                    }
+                };
+
+                // if id does not exist, then error was reported above
+                self.env.borrow_mut().set(id, new_type);
+            }
+        };
+    }
+
     fn check_statement_if_then_else(&mut self,
                                     statement: &StmtNode,
                                     if_then_stmt: &IfThenStmt)

tests/run-pass/compound-assign.bl

@@ -0,0 +1,13 @@
+var s = "Hello";
+s += ", world!";
+assert_eq(s, "Hello, world!");
+
+var x = 5;
+x += 5;
+assert_eq(x, 10);
+x -= 5;
+assert_eq(x, 5);
+x *= 2;
+assert_eq(x, 10);
+x /= 2;
+assert_eq(x, 5);

tests/typecheck-fail/compound-assign-binary-error.bl

@@ -0,0 +1,2 @@
+var x = true;
+x += 1;

tests/typecheck-fail/compound-assign-binary-error.err

@@ -0,0 +1 @@
+[(RuntimeError(BinaryTypeError(Add, Bool, Number)), (14, 21))]

tests/typecheck-pass/compound-assign.bl

@@ -0,0 +1,8 @@
+var s = "Hello";
+s += ", world!";
+
+var x = 5;
+x += 5;
+x -= 5;
+x *= 2;
+x /= 2;