Rollup merge of #41838 - z1mvader:fix_fn_args_coerce_closure, r=nikomatsakis

Fixed argument inference for closures when coercing into 'fn'

This fixes https://github.com/rust-lang/rust/issues/41755. The tests  `compile-fail/closure-no-fn.rs` and `compile-fail/issue-40000.rs` were modified. A new test `run-pass/closure_to_fn_coercion-expected-types.rs` was added

r? @nikomatsakis

1 files changed, 17 insertions, 0 deletions

diff --git a/src/test/run-pass/closure_to_fn_coercion-expected-types.rs b/src/test/run-pass/closure_to_fn_coercion-expected-types.rs
new file mode 100644
index 00000000000..7214ebfaf07
--- /dev/null
+++ b/src/test/run-pass/closure_to_fn_coercion-expected-types.rs
@@ -0,0 +1,17 @@
+// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+// Ensure that we deduce expected argument types when a `fn()` type is expected (#41755)
+
+#![feature(closure_to_fn_coercion)]
+fn foo(f: fn(Vec<u32>) -> usize) { }
+
+fn main() {
+    foo(|x| x.len())
+}