gnu: rust: Bootstrap (only) Rust 1.19.0 by mrustc.

* gnu/packages/patches/rust-1.19-mrustc.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add it.
* gnu/packages/rust.scm (rust-1.19)[source]: Add patch
"rust-1.19-mrustc.patch".
[arguments]<#:modules>: New field.
<#:phases>[patch-cargo-tomls]: New phase.
<#:phases>[build]: Modify.
<#:phases>[install]: Modify.
[native-inputs]: Replace rust-bootstrap by mrustc.
(rust-1.23)[native-inputs]: New field.
[arguments]<#:phases>: Delete phase "patch-cargo-tomls".

1 files changed, 28 insertions, 0 deletions

diff --git a/gnu/packages/patches/rust-1.19-mrustc.patch b/gnu/packages/patches/rust-1.19-mrustc.patch
new file mode 100644
index 0000000000..261162172e
--- /dev/null
+++ b/gnu/packages/patches/rust-1.19-mrustc.patch
@@ -0,0 +1,28 @@
+See https://github.com/thepowersgang/mrustc/archive/v0.8.0.tar.gz
+
+--- rustc-1.19.0-src-orig/src/libcore/intrinsics.rs
++++ rustc-1.19.0-src/src/libcore/intrinsics.rs
+@@ -678,5 +678,9 @@
+     pub fn min_align_of_val<T: ?Sized>(_: &T) -> usize;
+ 
++    /// Obtain the length of a slice pointer
++    #[cfg(rust_compiler="mrustc")]
++    pub fn mrustc_slice_len<T>(pointer: *const [T]) -> usize;
++
+     /// Gets a static string slice containing the name of a type.
+     pub fn type_name<T: ?Sized>() -> &'static str;
+
+--- rustc-1.19.0-src-orig/src/libcore/slice/mod.rs
++++ rustc-1.19.0-src/src/libcore/slice/mod.rs
+@@ -413,6 +413,8 @@
+     #[inline]
+     fn len(&self) -> usize {
+-        unsafe {
+-            mem::transmute::<&[T], Repr<T>>(self).len
+-        }
++        #[cfg(not(rust_compiler="mrustc"))]
++        let rv = unsafe { mem::transmute::<&[T], Repr<T>>(self).len };
++        #[cfg(rust_compiler="mrustc")]
++        let rv = unsafe { ::intrinsics::mrustc_slice_len(self) };
++        rv
+     }