From 065c0e874abefedde129d33fe3bf3e16b2409acc Mon Sep 17 00:00:00 2001
From: Aaron Long <aaron.long.c@gmail.com>
Date: Fri, 5 Mar 2021 22:56:48 -0500
Subject: [PATCH] Begin async list comprehension implementation

---
 compiler/src/compile.rs | 38 +++++++++++++++++++++++++++-----------
 1 file changed, 27 insertions(+), 11 deletions(-)

diff --git a/compiler/src/compile.rs b/compiler/src/compile.rs
index e25bd7c01f..70a5b56022 100644
--- a/compiler/src/compile.rs
+++ b/compiler/src/compile.rs
@@ -2258,9 +2258,9 @@ impl Compiler {
 
         let mut loop_labels = vec![];
         for generator in generators {
-            if generator.is_async {
-                unimplemented!("async for comprehensions");
-            }
+            // if generator.is_async {
+            //     unimplemented!("async for comprehensions");
+            // }
 
             // Setup for loop:
             self.emit(Instruction::SetupLoop);
@@ -2271,21 +2271,37 @@ impl Compiler {
             } else {
                 // Evaluate iterated item:
                 self.compile_expression(&generator.iter)?;
-
-                // Get iterator / turn item into an iterator
-                self.emit(Instruction::GetIter);
             }
 
             let loop_block = self.new_block();
             let after_block = self.new_block();
             loop_labels.push((loop_block, after_block));
 
-            self.switch_to_block(loop_block);
-            self.emit(Instruction::ForIter {
-                target: after_block,
-            });
+            if generator.is_async {
+                let check_asynciter_block = self.new_block();
+
+                self.emit(Instruction::GetAIter);
+                self.switch_to_block(loop_block);
+                self.emit(Instruction::SetupExcept {
+                    handler: check_asynciter_block,
+                });
+                self.emit(Instruction::GetANext);
+                self.emit_constant(ConstantData::None);
+                self.emit(Instruction::YieldFrom);
+                self.compile_store(&generator.target)?;
+                self.emit(Instruction::PopBlock);
+
+            } else {
+                // Get iterator / turn item into an iterator
+                self.emit(Instruction::GetIter);
 
-            self.compile_store(&generator.target)?;
+                self.switch_to_block(loop_block);
+                self.emit(Instruction::ForIter {
+                    target: after_block,
+                });
+
+                self.compile_store(&generator.target)?;
+            }
 
             // Now evaluate the ifs:
             for if_condition in &generator.ifs {