moved renamed docs formatted | diverging-fallback-method-chain.rs

Author: Kivooeo

tests/ui/diverging-fallback-method-chain.rs

@@ -0,0 +1,21 @@
+//! Test type inference in method chains with diverging fallback.
+//! Verifies that closure type in `unwrap_or_else` is properly inferred
+//! when chained with other combinators and contains a diverging path.
+
+#![allow(unused)] // Less intrusive than allow(unused_imports)
+
+use std::num::ParseIntError;
+
+fn produce<T>() -> Result<&'static str, T> {
+    Ok("22")
+}
+
+fn main() {
+    // The closure's error type `T` must unify with `ParseIntError`,
+    // while the success type must be `usize` (from parse())
+    let x: usize = produce()
+        .and_then(|x| x.parse::<usize>()) // Explicit turbofish for clarity
+        .unwrap_or_else(|_| panic!());    // Diverging fallback
+
+    assert_eq!(x, 22);
+}