Better panic message (#117)

* Improve panic message when calling unloaded function

* Bump version

CHANGELOG.md

@@ -1,3 +1,8 @@
+## [1.0.1] - 2020-10-01
+
+### Changed
+- Improved panic error message when calling an unloaded function
+
 ## [1.0.0] - 2020-07-14
 
 ### Changed

Cargo.toml

@@ -3,7 +3,7 @@
 name = "clang-sys"
 authors = ["Kyle Mayes <kyle@mayeses.com>"]
 
-version = "1.0.0"
+version = "1.0.1"
 
 readme = "README.md"
 license = "Apache-2.0"

src/link.rs

@@ -155,10 +155,12 @@ macro_rules! link {
             $(#[doc=$doc] #[cfg($cfg)])*
             pub unsafe fn $name($($pname: $pty), *) $(-> $ret)* {
                 let f = with_library(|l| {
-                    match l.functions.$name {
-                        Some(f) => f,
-                        _ => panic!(concat!("function not loaded: ", stringify!($name))),
-                    }
+                    l.functions.$name.expect(concat!(
+                        "`libclang` function not loaded: `",
+                        stringify!($name),
+                        "`. This crate requires that `libclang` 3.9 or later be installed on your ",
+                        "system. For more information on how to accomplish this, see here: ",
+                        "https://rust-lang.github.io/rust-bindgen/requirements.html#installing-clang-39"))
                 }).expect("a `libclang` shared library is not loaded on this thread");
                 f($($pname), *)
             }