dev-lang/rust: 1.33.0 requires llvm:7 to build

improve llvm handling for future use, taken from mesa ebuild
make sure 1.33 pulls only llvm:7

Bug: https://bugs.gentoo.org/681108
Package-Manager: Portage-2.3.62, Repoman-2.3.12
Signed-off-by: Georgy Yakovlev <gyakovlev@gentoo.org>

diff --git a/dev-lang/rust/rust-1.33.0.ebuild b/dev-lang/rust/rust-1.33.0.ebuild
index aff9229221d00e70ee1167335485ac5e02250096..0cc4462509e3797ab1bd06c7531d6d4ef0016f3b 100644 (file)
--- a/dev-lang/rust/rust-1.33.0.ebuild
+++ b/dev-lang/rust/rust-1.33.0.ebuild
@@ -5,8 +5,6 @@ EAPI=6
 
 PYTHON_COMPAT=( python2_7 python3_{5,6,7} pypy )
 
-LLVM_MAX_SLOT=8
-
 inherit check-reqs eapi7-ver estack flag-o-matic llvm multiprocessing multilib-build python-any-r1 rust-toolchain toolchain-funcs
 
 if [[ ${PV} = *beta* ]]; then
@@ -40,13 +38,34 @@ LICENSE="|| ( MIT Apache-2.0 ) BSD-1 BSD-2 BSD-4 UoI-NCSA"
 
 IUSE="clippy cpu_flags_x86_sse2 debug doc libressl rls rustfmt system-llvm wasm ${ALL_LLVM_TARGETS[*]}"
 
-COMMON_DEPEND="sys-libs/zlib
-               !libressl? ( dev-libs/openssl:0= )
-               libressl? ( dev-libs/libressl:0= )
-               net-libs/libssh2
-               net-libs/http-parser:=
-               net-misc/curl[ssl]
-               system-llvm? ( >=sys-devel/llvm-7:= )"
+# Please keep the LLVM dependency block separate. Since LLVM is slotted,
+# we need to *really* make sure we're not pulling one than more slot
+# simultaneously.
+
+# How to use it:
+# 1. List all the working slots (with min versions) in ||, newest first.
+# 2. Update the := to specify *max* version, e.g. < 8.
+# 3. Specify LLVM_MAX_SLOT, e.g. 7.
+LLVM_DEPEND="
+       || (
+               sys-devel/llvm:7
+       )
+       <sys-devel/llvm-8:=
+"
+LLVM_MAX_SLOT=7
+
+COMMON_DEPEND="
+       sys-libs/zlib
+       !libressl? ( dev-libs/openssl:0= )
+       libressl? ( dev-libs/libressl:0= )
+       net-libs/libssh2
+       net-libs/http-parser:=
+       net-misc/curl[ssl]
+       system-llvm? (
+               ${LLVM_DEPEND}
+       )
+"
+
 DEPEND="${COMMON_DEPEND}
        ${PYTHON_DEPS}
        || (
@@ -91,9 +110,7 @@ pkg_pretend() {
 pkg_setup() {
        pre_build_checks
        python-any-r1_pkg_setup
-       if use system-llvm; then
-               llvm_pkg_setup
-       fi
+       use system-llvm && llvm_pkg_setup
 }
 
 src_prepare() {