From 713a6da2b59e792af72d257d04feb709d5920d37 Mon Sep 17 00:00:00 2001
From: Erik Demaine <edemaine@mit.edu>
Date: Thu, 26 Dec 2024 08:37:40 -0500
Subject: [PATCH] Fix top-level `yield` in `iife` mode

Fixes #1659
---
 source/parser.hera        | 1 +
 source/parser/lib.civet   | 4 +++-
 source/parser/types.civet | 1 +
 test/iife.civet           | 9 +++++++++
 4 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/source/parser.hera b/source/parser.hera
index 63a70100..3155a6c7 100644
--- a/source/parser.hera
+++ b/source/parser.hera
@@ -222,6 +222,7 @@ Program
       bare: true,
       root: true,
       topLevelAwait: hasAwait(statements),
+      topLevelYield: hasYield(statements),
     }
     processProgram(program)
     return program
diff --git a/source/parser/lib.civet b/source/parser/lib.civet
index 4ddf2f57..2c9639ab 100644
--- a/source/parser/lib.civet
+++ b/source/parser/lib.civet
@@ -1549,8 +1549,10 @@ function processProgram(root: BlockStatement): void
   let rootIIFE: ASTNode
   if config.iife or config.repl
     // Avoid top-level await if code is async (same as CoffeeScript),
+    // and avoid top-level yield* if code is a generator,
     // so that code works in CommonJS environment and so REPL can eval it
-    rootIIFE = wrapIIFE root.expressions, root.topLevelAwait
+    rootIIFE = wrapIIFE root.expressions, root.topLevelAwait,
+      if root.topLevelYield then "*"
     newExpressions: StatementTuple[] := [['', rootIIFE]]
     root.children = root.children.map & is root.expressions ? newExpressions : &
     root.expressions = newExpressions
diff --git a/source/parser/types.civet b/source/parser/types.civet
index a007a685..933abf8c 100644
--- a/source/parser/types.civet
+++ b/source/parser/types.civet
@@ -601,6 +601,7 @@ export type BlockStatement =
   implicitlyReturned?: boolean  // fat arrow function with no braces
   root?: boolean  // is this the global root block for the program?
   topLevelAwait?: boolean // for root block, is there top-level `await`? (before any IIFE wrapping)
+  topLevelYield?: boolean // for root block, is there top-level `yield`? (before any IIFE wrapping)
   parent?: Parent
 
 export type ImportDeclaration
diff --git a/test/iife.civet b/test/iife.civet
index a1527292..5f29d3d4 100644
--- a/test/iife.civet
+++ b/test/iife.civet
@@ -38,6 +38,15 @@ describe "iife directive", ->
     (async ()=>{return console.log((await fetch('https://civet.dev')).status)})()
   """
 
+  testCase """
+    generator
+    ---
+    "civet iife"
+    yield 5
+    ---
+    (function*(){yield 5})()
+  """
+
 describe "repl directive", ->
   testCase """
     top-level declarations