From f0e02a3aa32bee42b57d409f572dbd83ae227aa6 Mon Sep 17 00:00:00 2001
From: Olivier Goffart <olivier.goffart@slint.dev>
Date: Tue, 15 Oct 2024 11:15:41 +0200
Subject: [PATCH] Fix panic with invalid code

Fix #6518
---
 internal/compiler/passes/purity_check.rs      | 41 ++++++++++---------
 .../compiler/tests/syntax/fuzzing/6518.slint  | 14 +++++++
 2 files changed, 36 insertions(+), 19 deletions(-)
 create mode 100644 internal/compiler/tests/syntax/fuzzing/6518.slint

diff --git a/internal/compiler/passes/purity_check.rs b/internal/compiler/passes/purity_check.rs
index efdb7aa5981..fcd8fdc22a5 100644
--- a/internal/compiler/passes/purity_check.rs
+++ b/internal/compiler/passes/purity_check.rs
@@ -70,28 +70,31 @@ fn ensure_pure(
                 }
                 None => {
                     if recursion_test.insert(nr.clone()) {
-                        if !ensure_pure(
-                            &nr.element()
-                                .borrow()
-                                .bindings
-                                .get(nr.name())
-                                .expect("private function must be local and defined")
-                                .borrow()
-                                .expression,
-                            None,
-                            level,
-                            recursion_test,
-                        ) {
-                            if let Some(diag) = diag.as_deref_mut() {
-                                diag.push_diagnostic(
-                                    format!("Call of impure function '{}'", nr.name()),
-                                    node,
-                                    level,
+                        match nr.element().borrow().bindings.get(nr.name()) {
+                            None => {
+                                debug_assert!(
+                                    diag.as_ref().map_or(true, |d| d.has_errors()),
+                                    "private functions must be local and defined"
                                 );
                             }
-                            r = false;
+                            Some(binding) => {
+                                if !ensure_pure(
+                                    &binding.borrow().expression,
+                                    None,
+                                    level,
+                                    recursion_test,
+                                ) {
+                                    if let Some(diag) = diag.as_deref_mut() {
+                                        diag.push_diagnostic(
+                                            format!("Call of impure function '{}'", nr.name()),
+                                            node,
+                                            level,
+                                        );
+                                    }
+                                    r = false;
+                                }
+                            }
                         }
-                        recursion_test.remove(nr);
                     }
                 }
             }
diff --git a/internal/compiler/tests/syntax/fuzzing/6518.slint b/internal/compiler/tests/syntax/fuzzing/6518.slint
new file mode 100644
index 00000000000..362a90967ae
--- /dev/null
+++ b/internal/compiler/tests/syntax/fuzzing/6518.slint
@@ -0,0 +1,14 @@
+// Copyright © SixtyFPS GmbH <info@slint.dev>
+// SPDX-License-Identifier: GPL-3.0-only OR LicenseRef-Slint-Royalty-free-2.0 OR LicenseRef-Slint-Software-3.0
+
+Compo1:=R{property<int b;function bb)i{}}c:=Compo1{b:self.bb
+//                     ^error{Syntax error: expected '>'}
+//                                  ^^error{Syntax error: expected '\('}
+//                                  ^^^error{Syntax error: expected '\{'}
+//                                  ^^^^error{invalid expression}
+//                                  ^^^^^error{Syntax error: expected '\}'}
+//                                  ^^^^^^error{Parse error}
+
+   }
+// ^error{Syntax error: expected ';'}
+    /**/