Make return statements legal in block expressions

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 `$$`.
 

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 "<"', () => {

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;