throw takes an expression

src/parser/parser2.ts

@@ -729,7 +729,7 @@ export class Parser {
   // throw blah
   throw(): SyntaxNode {
     const keyword = this.keyword('throw')
-    const val = this.value()
+    const val = this.expression()
     const node = new SyntaxNode('Throw', keyword.from, val.to)
     return node.push(keyword, val)
   }

src/parser/tests/exceptions.test.ts

@@ -139,6 +139,18 @@ describe('try/catch/finally/throw', () => {
     `)
   })
 
+  test('parses throw statement with BinOp', () => {
+    expect("throw 'error message:' + msg").toMatchTree(`
+      Throw
+        keyword throw
+        BinOp
+          String
+            StringFragment error message:
+          Plus +
+          Identifier msg
+    `)
+  })
+
   test('parses throw statement with identifier', () => {
     expect('throw error-object').toMatchTree(`
       Throw