From 690faa6b79f6f70743fcc68b9a0a2730f0228019 Mon Sep 17 00:00:00 2001
From: Luke Boswell <lukewilliamboswell@gmail.com>
Date: Sat, 23 Nov 2024 12:22:54 +1100
Subject: [PATCH] add roc_expect_failed

---
 crates/roc_host/src/glue.rs | 20 ++++++++++++++++++++
 crates/roc_host/src/lib.rs  | 23 +++++++++++++++++++++++
 2 files changed, 43 insertions(+)

diff --git a/crates/roc_host/src/glue.rs b/crates/roc_host/src/glue.rs
index f81c9c3..f10a0ee 100644
--- a/crates/roc_host/src/glue.rs
+++ b/crates/roc_host/src/glue.rs
@@ -92,3 +92,23 @@ impl From<std::io::Error> for IOErr {
         }
     }
 }
+
+#[repr(C)]
+pub struct Variable {
+    pub name: RocStr,
+    pub value: RocStr,
+}
+
+impl roc_std::RocRefcounted for Variable {
+    fn inc(&mut self) {
+        self.name.inc();
+        self.value.inc();
+    }
+    fn dec(&mut self) {
+        self.name.dec();
+        self.value.dec();
+    }
+    fn is_refcounted() -> bool {
+        true
+    }
+}
diff --git a/crates/roc_host/src/lib.rs b/crates/roc_host/src/lib.rs
index dca4167..c130d76 100644
--- a/crates/roc_host/src/lib.rs
+++ b/crates/roc_host/src/lib.rs
@@ -129,6 +129,29 @@ pub unsafe extern "C" fn roc_dbg(loc: &RocStr, msg: &RocStr, src: &RocStr) {
     eprintln!("[{}] {} = {}", loc, src, msg);
 }
 
+/// # Safety
+///
+/// This function is unsafe.
+#[no_mangle]
+pub unsafe extern "C" fn roc_expect_failed(
+    loc: &RocStr,
+    src: &RocStr,
+    variables: &RocList<glue::Variable>,
+) {
+    eprintln!("\nExpectation failed at {}:", loc.as_str());
+    eprintln!("\nExpression:\n\t{}\n", src.as_str());
+
+    if !variables.is_empty() {
+        eprintln!("With values:");
+        for var in variables.iter() {
+            eprintln!("\t{} = {}", var.name.as_str(), var.value.as_str());
+        }
+        eprintln!();
+    }
+
+    std::process::exit(1);
+}
+
 /// # Safety
 ///
 /// This function is unsafe.