WIP: Implement the return statement

sixtyfps_compiler/expression_tree.rs

@@ -363,6 +363,8 @@ pub enum Expression {
     EasingCurve(EasingCurve),
 
     EnumerationValue(EnumerationValue),
+
+    ReturnStatement(Option<Box<Expression>>),
 }
 
 impl Default for Expression {
@@ -469,6 +471,7 @@ impl Expression {
             Expression::ReadLocalVariable { ty, .. } => ty.clone(),
             Expression::EasingCurve(_) => Type::Easing,
             Expression::EnumerationValue(value) => Type::Enumeration(value.enumeration.clone()),
+            Expression::ReturnStatement(expr) => expr.as_ref().map_or(Type::Void, |expr| expr.ty()),
         }
     }
 
@@ -542,6 +545,9 @@ impl Expression {
             Expression::ReadLocalVariable { .. } => {}
             Expression::EasingCurve(_) => {}
             Expression::EnumerationValue(_) => {}
+            Expression::ReturnStatement(expr) => {
+                expr.as_deref().map(|expr| visitor(expr));
+            }
         }
     }
 
@@ -614,6 +620,9 @@ impl Expression {
             Expression::ReadLocalVariable { .. } => {}
             Expression::EasingCurve(_) => {}
             Expression::EnumerationValue(_) => {}
+            Expression::ReturnStatement(expr) => {
+                expr.as_deref_mut().map(|expr| visitor(expr));
+            }
         }
     }
 
@@ -666,6 +675,9 @@ impl Expression {
             Expression::ReadLocalVariable { .. } => false,
             Expression::EasingCurve(_) => true,
             Expression::EnumerationValue(_) => true,
+            Expression::ReturnStatement(expr) => {
+                expr.as_ref().map_or(true, |expr| expr.is_constant())
+            }
         }
     }
 
@@ -676,6 +688,13 @@ impl Expression {
         node: &impl SpannedWithSourceFile,
         diag: &mut BuildDiagnostics,
     ) -> Expression {
+        if let Expression::ReturnStatement(expr) = self {
+            return Expression::ReturnStatement(expr.map(|mut expr| {
+                let expr = std::mem::replace(&mut *expr, Expression::Invalid);
+                Box::new(expr.maybe_convert_to(target_type, node, diag))
+            }));
+        }
+
         let ty = self.ty();
         if ty == target_type || target_type == Type::Void || target_type == Type::Invalid {
             self

sixtyfps_compiler/generator/cpp.rs

@@ -1452,8 +1452,18 @@ fn compile_expression(
             }
         }
         Expression::CodeBlock(sub) => {
-            let mut x = sub.iter().map(|e| compile_expression(e, component)).collect::<Vec<_>>();
+            let len = sub.len();
+            let mut x = sub.iter().enumerate().map(|(i, e)| {
+                match e {
+                    Expression::ReturnStatement(return_expr) if i == len - 1 => {
+                        return_expr.as_ref().map_or_else(String::new, |return_expr| compile_expression(return_expr, component))
+                    },
+                    e => compile_expression(e, component)
+                }
+
+            }).collect::<Vec<_>>();
             if let Some(s) = x.last_mut() { *s = format!("return {};", s) };
+
             format!("[&]{{ {} }}()", x.join(";"))
         }
         Expression::FunctionCall { function, arguments, source_location: _  } => match &**function {
@@ -1608,6 +1618,7 @@ fn compile_expression(
         }
         Expression::Uncompiled(_) | Expression::TwoWayBinding(..) => panic!(),
         Expression::Invalid => "\n#error invalid expression\n".to_string(),
+        Expression::ReturnStatement(expr) => format!("return {};", expr.as_ref().map_or_else(String::new, |expr| compile_expression(expr, component))),
     }
 }
 

sixtyfps_compiler/generator/rust.rs

@@ -1296,6 +1296,10 @@ fn compile_expression(expr: &Expression, component: &Rc<Component>) -> TokenStre
             let value_ident = format_ident!("{}", value.to_string());
             quote!(sixtyfps::re_exports::#base_ident::#value_ident)
         }
+        Expression::ReturnStatement(expr) => {
+            let return_expr = expr.as_ref().map(|expr| compile_expression(expr, component));
+            quote!(return (#return_expr) as _;)
+        },
     }
 }
 

sixtyfps_compiler/passes/resolving.rs

@@ -269,11 +269,49 @@ impl Expression {
 
     fn from_codeblock_node(node: syntax_nodes::CodeBlock, ctx: &mut LookupCtx) -> Expression {
         debug_assert_eq!(node.kind(), SyntaxKind::CodeBlock);
-        Expression::CodeBlock(
-            node.children()
-                .filter(|n| n.kind() == SyntaxKind::Expression)
-                .map(|n| Self::from_expression_node(n.into(), ctx))
-                .collect(),
+
+        let mut statements_or_exprs = node
+            .children()
+            .filter_map(|n| match n.kind() {
+                SyntaxKind::Expression => Some(Self::from_expression_node(n.into(), ctx)),
+                SyntaxKind::ReturnStatement => Some(Self::from_return_statement(n.into(), ctx)),
+                _ => None,
+            })
+            .collect::<Vec<_>>();
+
+        let exit_points_and_return_types = statements_or_exprs
+            .iter()
+            .enumerate()
+            .filter_map(|(index, statement_or_expr)| {
+                if index == statements_or_exprs.len()
+                    || matches!(statement_or_expr, Expression::ReturnStatement(..))
+                {
+                    Some((index, statement_or_expr.ty()))
+                } else {
+                    None
+                }
+            })
+            .collect::<Vec<_>>();
+
+        let common_return_type = Self::common_target_type_for_type_list(
+            exit_points_and_return_types.iter().map(|(_, ty)| ty.clone()),
+        );
+
+        exit_points_and_return_types.into_iter().for_each(|(index, _)| {
+            let mut expr = std::mem::replace(&mut statements_or_exprs[index], Expression::Invalid);
+            expr = expr.maybe_convert_to(common_return_type.clone(), &node, &mut ctx.diag);
+            statements_or_exprs[index] = expr;
+        });
+
+        Expression::CodeBlock(statements_or_exprs)
+    }
+
+    fn from_return_statement(
+        node: syntax_nodes::ReturnStatement,
+        ctx: &mut LookupCtx,
+    ) -> Expression {
+        Expression::ReturnStatement(
+            node.Expression().map(|n| Box::new(Self::from_expression_node(n.into(), ctx))),
         )
     }
 

sixtyfps_runtime/interpreter/eval.rs

@@ -360,6 +360,9 @@ pub fn eval_expression(e: &Expression, local_context: &mut EvalLocalContext) ->
         Expression::CodeBlock(sub) => {
             let mut v = Value::Void;
             for e in sub {
+                if let Expression::ReturnStatement(expr) = e {
+                    return expr.as_ref().map_or(Value::Void, |expr| eval_expression(expr, local_context))
+                }
                 v = eval_expression(e, local_context);
             }
             v
@@ -606,6 +609,7 @@ pub fn eval_expression(e: &Expression, local_context: &mut EvalLocalContext) ->
         Expression::EnumerationValue(value) => {
             Value::EnumerationValue(value.enumeration.name.clone(), value.to_string())
         }
+        Expression::ReturnStatement(_) => panic!("internal error: return statement must only appear inside code block and handled there")
     }
 }
 

tests/cases/expr/return.60

@@ -0,0 +1,46 @@
+/* LICENSE BEGIN
+    This file is part of the SixtyFPS Project -- https://sixtyfps.io
+    Copyright (c) 2020 Olivier Goffart <olivier.goffart@sixtyfps.io>
+    Copyright (c) 2020 Simon Hausmann <simon.hausmann@sixtyfps.io>
+
+    SPDX-License-Identifier: GPL-3.0-only
+    This file is also available under commercial licensing terms.
+    Please contact info@sixtyfps.io for more information.
+LICENSE END */
+ TestCase := Rectangle {
+    property <bool> toggle;
+    property <int> value: {
+        if (toggle) {
+            return 42;
+        }
+        return 100;
+    }
+
+    signal test_signal;
+    property <bool> block_signal;
+    property <bool> signal_handled;
+    test_signal => {
+        if (block_signal) {
+            return;
+        }
+        signal_handled = true;
+    }
+}
+/*
+```cpp
+auto handle = TestCase::create();
+const TestCase &instance = *handle;
+assert_eq(instance.get_value(), 100);
+instance.set_toggle(true);
+assert_eq(instance.get_value(), 42);
+
+instance.emit_test_signal();
+assert(instance.get_signal_handled());
+
+instance.set_signal_handled(false);
+instance.set_block_signal(true);
+instance.emit_test_signal();
+assert(!instance.get_signal_handled());
+```
+
+*/