From 44bc51ba4fef66b7778668b3877a65425ac2eedc Mon Sep 17 00:00:00 2001
From: Leedehai <18319900+Leedehai@users.noreply.github.com>
Date: Tue, 30 Apr 2024 08:30:38 -0400
Subject: [PATCH] Let let-binding raise error on unexpected keywords (#4034)

---
 crates/typst-syntax/src/parser.rs | 11 +++++------
 tests/suite/scripting/let.typ     | 17 +++++++++++++++++
 2 files changed, 22 insertions(+), 6 deletions(-)

diff --git a/crates/typst-syntax/src/parser.rs b/crates/typst-syntax/src/parser.rs
index e61618e0..d8ac1198 100644
--- a/crates/typst-syntax/src/parser.rs
+++ b/crates/typst-syntax/src/parser.rs
@@ -1452,12 +1452,11 @@ fn pattern_leaf<'s>(
     seen: &mut HashSet<&'s str>,
     dupe: Option<&'s str>,
 ) {
-    if !p.at_set(set::PATTERN_LEAF) {
-        if p.current().is_keyword() {
-            p.eat_and_get().expected("pattern");
-        } else {
-            p.expected("pattern");
-        }
+    if p.current().is_keyword() {
+        p.eat_and_get().expected("pattern");
+        return;
+    } else if !p.at_set(set::PATTERN_LEAF) {
+        p.expected("pattern");
         return;
     }
 
diff --git a/tests/suite/scripting/let.typ b/tests/suite/scripting/let.typ
index 2604c4ea..aafc6579 100644
--- a/tests/suite/scripting/let.typ
+++ b/tests/suite/scripting/let.typ
@@ -141,3 +141,20 @@ Three
 // ... where this wasn't.
 // Error: 12 expected equals sign
 #let (a, b)
+
+--- issue-4027-let-binding-with-keyword-context ---
+// Error: 6-13 expected pattern, found keyword `context`
+// Hint: 6-13 keyword `context` is not allowed as an identifier; try `context_` instead
+#let context = 5
+
+--- issue-4027-let-binding-with-keyword-let ---
+// Error: 6-9 expected pattern, found keyword `let`
+// Hint: 6-9 keyword `let` is not allowed as an identifier; try `let_` instead
+#let let = 5
+
+--- issue-4027-let-binding-with-destructured-keywords ---
+// Error: 7-14 expected pattern, found keyword `context`
+// Hint: 7-14 keyword `context` is not allowed as an identifier; try `context_` instead
+// Error: 21-24 expected pattern, found keyword `let`
+// Hint: 21-24 keyword `let` is not allowed as an identifier; try `let_` instead
+#let (context, foo, let) = (5, 6, 7)