From 58f799c41cb71f167e6e82eb94b3cde1303de11e Mon Sep 17 00:00:00 2001
From: Laurenz <laurmaedje@gmail.com>
Date: Fri, 12 Feb 2021 23:06:04 +0100
Subject: [PATCH] =?UTF-8?q?Early=20quit=20loop=20when=20body=20returns=20e?=
 =?UTF-8?q?rror=20=F0=9F=9B=91?=
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---
 src/eval/mod.rs             | 38 +++++++++++++++++++------------------
 tests/lang/typ/for-loop.typ |  7 +++++++
 2 files changed, 27 insertions(+), 18 deletions(-)

diff --git a/src/eval/mod.rs b/src/eval/mod.rs
index 47f997eb4..98030b869 100644
--- a/src/eval/mod.rs
+++ b/src/eval/mod.rs
@@ -429,57 +429,59 @@ impl Eval for ExprFor {
 
     fn eval(&self, ctx: &mut EvalContext) -> Self::Output {
         macro_rules! iter {
-            (for ($($binding:ident => $value:ident),*) in $iter:expr) => {{
+            (for ($($binding:ident => $value:ident),*) in $iter:expr) => {
                 let mut output = vec![];
+                ctx.scopes.push();
 
                 #[allow(unused_parens)]
                 for ($($value),*) in $iter {
                     $(ctx.scopes.def_mut($binding.as_str(), $value);)*
 
-                    if let Value::Template(new) = self.body.eval(ctx) {
-                        output.extend(new);
+                    match self.body.eval(ctx) {
+                        Value::Template(new) => output.extend(new),
+                        Value::Error => {
+                            ctx.scopes.pop();
+                            return Value::Error;
+                        }
+                        _ => {}
                     }
                 }
 
-                Value::Template(output)
-            }};
+                ctx.scopes.pop();
+                return Value::Template(output);
+            };
         }
 
-        ctx.scopes.push();
-
         let iter = self.iter.eval(ctx);
-        let value = match (self.pattern.clone(), iter) {
+        match (self.pattern.clone(), iter) {
             (ForPattern::Value(v), Value::Str(string)) => {
-                iter!(for (v => value) in string.chars().map(|c| Value::Str(c.into())))
+                iter!(for (v => value) in string.chars().map(|c| Value::Str(c.into())));
             }
             (ForPattern::Value(v), Value::Array(array)) => {
-                iter!(for (v => value) in array.into_iter())
+                iter!(for (v => value) in array.into_iter());
             }
             (ForPattern::Value(v), Value::Dict(dict)) => {
-                iter!(for (v => value) in dict.into_iter().map(|p| p.1))
+                iter!(for (v => value) in dict.into_iter().map(|p| p.1));
             }
             (ForPattern::KeyValue(k, v), Value::Dict(dict)) => {
-                iter!(for (k => key, v => value) in dict.into_iter())
+                iter!(for (k => key, v => value) in dict.into_iter());
             }
 
             (ForPattern::KeyValue(_, _), Value::Str(_))
             | (ForPattern::KeyValue(_, _), Value::Array(_)) => {
                 ctx.diag(error!(self.pattern.span(), "mismatched pattern"));
-                Value::Error
             }
 
-            (_, Value::Error) => Value::Error,
+            (_, Value::Error) => {}
             (_, iter) => {
                 ctx.diag(error!(
                     self.iter.span(),
                     "cannot loop over {}",
                     iter.type_name(),
                 ));
-                Value::Error
             }
-        };
+        }
 
-        ctx.scopes.pop();
-        value
+        Value::Error
     }
 }
diff --git a/tests/lang/typ/for-loop.typ b/tests/lang/typ/for-loop.typ
index 944cef1ea..2af7ab04b 100644
--- a/tests/lang/typ/for-loop.typ
+++ b/tests/lang/typ/for-loop.typ
@@ -42,3 +42,10 @@
 // Make sure that we don't complain twice.
 // Error: 12-19 cannot add integer and string
 #for v #in 1 + "2" {}
+
+// Error: 14-17 cannot apply '-' to string
+#let error = -""
+#let result = #for v #in (1, 2, 3) {
+    #if v < 2 [Ok] #else {error}
+}
+#[test result, error]