Add control flow types

schala-lang/language/src/ast/mod.rs

@@ -54,6 +54,14 @@ pub enum StatementKind {
     Declaration(Declaration),
     Import(ImportSpecifier),
     Module(ModuleSpecifier),
+    Flow(FlowControl),
+}
+
+#[derive(Debug, Clone, PartialEq)]
+pub enum FlowControl {
+    Continue,
+    Break,
+    Return(Option<Expression>),
 }
 
 #[derive(Debug, Clone, PartialEq, Default)]

schala-lang/language/src/ast/visitor.rs

@@ -47,6 +47,9 @@ pub fn walk_block<V: ASTVisitor>(v: &mut V, block: &Block) {
                 if let Recursion::Continue = v.module(module_spec) {
                     walk_block(v, &module_spec.contents);
                 },
+            Flow(ref _flow_control) => {
+                //TODO do something with flow control in Visitor
+            }
         }
     }
 }

schala-lang/language/src/ast/visualize.rs

@@ -1,7 +1,9 @@
 #![allow(clippy::single_char_add_str)]
+use std::fmt::Write;
+
 use super::{
-    Block, Declaration, Expression, ExpressionKind, ImportSpecifier, InvocationArgument, ModuleSpecifier,
-    Signature, Statement, StatementKind, AST,
+    Block, Declaration, Expression, ExpressionKind, FlowControl, ImportSpecifier, InvocationArgument,
+    ModuleSpecifier, Signature, Statement, StatementKind, AST,
 };
 
 const LEVEL: usize = 2;
@@ -35,6 +37,7 @@ fn render_statement(stmt: &Statement, indent: usize, buf: &mut String) {
         Declaration(ref decl) => render_declaration(decl, indent, buf),
         Import(ref spec) => render_import(spec, indent, buf),
         Module(ref spec) => render_module(spec, indent, buf),
+        Flow(ref flow_control) => render_flow_control(flow_control, indent, buf),
     }
 }
 
@@ -191,6 +194,15 @@ fn render_module(_expr: &ModuleSpecifier, _indent: usize, buf: &mut String) {
     buf.push_str("(Module <some mod>)");
 }
 
+fn render_flow_control(flow: &FlowControl, _indent: usize, buf: &mut String) {
+    use FlowControl::*;
+    match flow {
+        Return(ref _expr) => write!(buf, "return <expr>").unwrap(),
+        Break => write!(buf, "break").unwrap(),
+        Continue => write!(buf, "continue").unwrap(),
+    }
+}
+
 #[cfg(test)]
 mod test {
     use super::render_ast;

schala-lang/language/src/parsing/mod.rs

@@ -15,7 +15,7 @@
 //! ```text
 //! program := (statement delimiter)* EOF
 //! delimiter := NEWLINE | ";"
-//! statement := expression | declaration | import | module
+//! statement := expression | declaration | import | module | flow
 //! block := "{" (statement delimiter)* "}"
 //! declaration := type_declaration | func_declaration | binding_declaration | impl_declaration
 //! ```
@@ -401,12 +401,28 @@ impl Parser {
             Keyword(Impl) => self.impl_declaration().map(StatementKind::Declaration),
             Keyword(Import) => self.import_declaration().map(StatementKind::Import),
             Keyword(Module) => self.module_declaration().map(StatementKind::Module),
+            Keyword(Continue) | Keyword(Return) | Keyword(Break) =>
+                self.flow_control().map(StatementKind::Flow),
             _ => self.expression().map(StatementKind::Expression),
         }?;
         let id = self.id_store.fresh();
         Ok(Statement { kind, id, location: tok.location })
     }
 
+    #[recursive_descent_method]
+    fn flow_control(&mut self) -> ParseResult<FlowControl> {
+        let tok = self.token_handler.next();
+        Ok(match tok.get_kind() {
+            Keyword(Continue) => FlowControl::Continue,
+            Keyword(Break) => FlowControl::Break,
+            Keyword(Return) => match self.token_handler.peek_kind() {
+                Semicolon | Newline => FlowControl::Return(None),
+                _ => FlowControl::Return(Some(self.expression()?)),
+            },
+            _ => unreachable!(),
+        })
+    }
+
     #[recursive_descent_method]
     fn annotation(&mut self) -> ParseResult<Declaration> {
         expect!(self, AtSign);

schala-lang/language/src/parsing/test.rs

@@ -1215,3 +1215,38 @@ if (45, "panda", false, 2.2) {
       )
     };
 }
+
+#[test]
+fn flow_control() {
+    use ExpressionKind::*;
+
+    // This is an incorrect program, but shoudl parse correctly.
+    let source = r#"
+    fn test() {
+        let a = 10;
+        break;
+        continue;
+        return;
+        return 10;
+    }"#;
+
+    assert_ast!(
+        source,
+        vec![fn_decl(
+            Signature { name: rc("test"), operator: false, type_anno: None, params: vec![] },
+            vec![
+                decl(Declaration::Binding {
+                    name: rc("a"),
+                    constant: true,
+                    type_anno: None,
+                    expr: expr(NatLiteral(10))
+                }),
+                stmt(StatementKind::Flow(FlowControl::Break)),
+                stmt(StatementKind::Flow(FlowControl::Continue)),
+                stmt(StatementKind::Flow(FlowControl::Return(None))),
+                stmt(StatementKind::Flow(FlowControl::Return(Some(expr(NatLiteral(10)))))),
+            ]
+            .into()
+        )]
+    );
+}

schala-lang/language/src/reduced_ir/mod.rs

@@ -80,6 +80,9 @@ impl<'a, 'b> Reducer<'a, 'b> {
             ast::StatementKind::Module(_modspec) => {
                 //TODO handle modules
             }
+            ast::StatementKind::Flow(..) => {
+                //TODO this should be an error
+            }
         }
     }
 
@@ -100,7 +103,18 @@ impl<'a, 'b> Reducer<'a, 'b> {
 
                 _ => None,
             },
-            _ => None,
+            ast::StatementKind::Module(_) | ast::StatementKind::Import(_) => {
+                //TODO need to handle function-internal modules, imports
+                None
+            }
+            ast::StatementKind::Flow(ast::FlowControl::Return(expr)) =>
+                if let Some(expr) = expr {
+                    Some(Statement::Return(self.expression(expr)))
+                } else {
+                    Some(Statement::Return(Expression::unit()))
+                },
+            ast::StatementKind::Flow(ast::FlowControl::Break) => Some(Statement::Break),
+            ast::StatementKind::Flow(ast::FlowControl::Continue) => Some(Statement::Continue),
         }
     }
 

schala-lang/language/src/reduced_ir/types.rs

@@ -42,6 +42,9 @@ impl ReducedIR {
 pub enum Statement {
     Expression(Expression),
     Binding { id: DefId, constant: bool, expr: Expression },
+    Return(Expression),
+    Continue,
+    Break,
 }
 
 #[derive(Debug, Clone)]

schala-lang/language/src/tokenizing.rs

@@ -86,11 +86,12 @@ pub enum Kw {
     Func,
     For,
     While,
-    Const,
     Let,
     In,
     Mut,
     Return,
+    Continue,
+    Break,
     Alias,
     Type,
     SelfType,
@@ -115,11 +116,12 @@ impl TryFrom<&str> for Kw {
             "fn" => Kw::Func,
             "for" => Kw::For,
             "while" => Kw::While,
-            "const" => Kw::Const,
             "let" => Kw::Let,
             "in" => Kw::In,
             "mut" => Kw::Mut,
             "return" => Kw::Return,
+            "break" => Kw::Break,
+            "continue" => Kw::Continue,
             "alias" => Kw::Alias,
             "type" => Kw::Type,
             "Self" => Kw::SelfType,

schala-lang/language/src/tree_walk_eval/evaluator.rs

@@ -58,6 +58,9 @@ impl<'a, 'b> Evaluator<'a, 'b> {
                 let evaluated = self.expression(expr)?;
                 Ok(Some(evaluated.into()))
             }
+            Statement::Return(expr) => unimplemented!(),
+            Statement::Break => unimplemented!(),
+            Statement::Continue => unimplemented!(),
         }
     }