From 0a7f0bc095465f5812341bad4c172b7a7d3055f5 Mon Sep 17 00:00:00 2001
From: Lumi Pakkanen <lumi.pakkanen@gmail.com>
Date: Tue, 18 Jun 2024 09:18:55 +0300
Subject: [PATCH] Make return statements legal in block expressions

---
 documentation/advanced-dsl.md           | 11 +++++++++++
 src/parser/__tests__/expression.spec.ts | 12 ++++++++++++
 src/parser/expression.ts                |  4 +++-
 3 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/documentation/advanced-dsl.md b/documentation/advanced-dsl.md
index cf76db4c..74744676 100644
--- a/documentation/advanced-dsl.md
+++ b/documentation/advanced-dsl.md
@@ -50,6 +50,17 @@ Blocks are valid expressions and evaluate to arrays. They have the lowest preced
 (* $ = [10, 20, 30] *)
 ```
 
+#### Block expression return value
+Use a `return` statement inside a block expression to evaluate to the returned value.
+```ocaml
+const foo = {
+  const bar = 2
+  const baz = 3
+  return bar + baz
+}
+(* const foo = 5 *)
+```
+
 ### Parent scale
 The current scale of the parent block can be accessed using `$$`.
 
diff --git a/src/parser/__tests__/expression.spec.ts b/src/parser/__tests__/expression.spec.ts
index 03d5ad38..79349cba 100644
--- a/src/parser/__tests__/expression.spec.ts
+++ b/src/parser/__tests__/expression.spec.ts
@@ -2460,6 +2460,18 @@ describe('SonicWeave expression evaluator', () => {
     expect(interval.value).toBeInstanceOf(TimeReal);
     expect(interval.valueOf()).toBeCloseTo(1.000000745, 10);
   });
+
+  it('allows return from block expressions', () => {
+    const foo = evaluate(`
+      const foo = ({
+        const ba = "ba"
+        return ba "r"
+        throw "not executed"
+      })
+      foo
+    `);
+    expect(foo).toBe('bar');
+  });
 });
 
 describe('Poor grammar / Fun with "<"', () => {
diff --git a/src/parser/expression.ts b/src/parser/expression.ts
index efa5d503..04184c45 100644
--- a/src/parser/expression.ts
+++ b/src/parser/expression.ts
@@ -429,7 +429,9 @@ export class ExpressionVisitor {
     const scale = this.currentScale;
     subVisitor.mutables.set('$$', scale);
     const interrupt = subVisitor.executeStatements(node.body);
-    if (interrupt) {
+    if (interrupt?.type === 'ReturnStatement') {
+      return interrupt.value;
+    } else if (interrupt) {
       throw new Error('Illegal interupt.');
     }
     return subVisitor.currentScale;