From 4f5194c89b20082940e66adcbb8bfb6ecf3d636e Mon Sep 17 00:00:00 2001
From: Danny McClanahan <1305167+cosmicexplorer@users.noreply.github.com>
Date: Tue, 24 Jul 2018 13:25:07 -0700
Subject: [PATCH] remove CToolchain/CppToolchain rules and add explanatory
 comment in environment.py

---
 .../pants/backend/native/config/environment.py     |  5 ++++-
 .../backend/native/subsystems/native_toolchain.py  | 14 --------------
 src/python/pants/backend/native/tasks/c_compile.py |  4 ++--
 .../pants/backend/native/tasks/cpp_compile.py      |  4 ++--
 4 files changed, 8 insertions(+), 19 deletions(-)

diff --git a/src/python/pants/backend/native/config/environment.py b/src/python/pants/backend/native/config/environment.py
index 70e9f3ba7a0b..a72c684cd68e 100644
--- a/src/python/pants/backend/native/config/environment.py
+++ b/src/python/pants/backend/native/config/environment.py
@@ -165,7 +165,10 @@ def as_invocation_environment_dict(self):
     return ret
 
 
-# TODO(#4020): These classes are performing the work of variants.
+# NB: These wrapper classes for LLVM and GCC toolchains are performing the work of variants. A
+# CToolchain cannot be requested directly, but native_toolchain.py provides an LLVMCToolchain,
+# which contains a CToolchain representing the clang compiler and a linker paired to work with
+# objects compiled by that compiler.
 class CToolchain(datatype([('c_compiler', CCompiler), ('c_linker', Linker)])): pass
 
 
diff --git a/src/python/pants/backend/native/subsystems/native_toolchain.py b/src/python/pants/backend/native/subsystems/native_toolchain.py
index 582ca564a001..c1e6279a5c72 100644
--- a/src/python/pants/backend/native/subsystems/native_toolchain.py
+++ b/src/python/pants/backend/native/subsystems/native_toolchain.py
@@ -291,18 +291,6 @@ def select_gcc_cpp_toolchain(platform, native_toolchain):
   yield GCCCppToolchain(CppToolchain(working_cpp_compiler, working_linker))
 
 
-@rule(CToolchain, [Select(NativeToolchain)])
-def select_default_c_toolchain(native_toolchain):
-  llvm_c_toolchain = yield Get(LLVMCToolchain, NativeToolchain, native_toolchain)
-  yield llvm_c_toolchain.c_toolchain
-
-
-@rule(CppToolchain, [Select(NativeToolchain)])
-def select_default_cpp_toolchain(native_toolchain):
-  llvm_cpp_toolchain = yield Get(LLVMCppToolchain, NativeToolchain, native_toolchain)
-  yield llvm_cpp_toolchain.cpp_toolchain
-
-
 def create_native_toolchain_rules():
   return [
     select_libc_dev,
@@ -313,7 +301,5 @@ def create_native_toolchain_rules():
     select_llvm_cpp_toolchain,
     select_gcc_c_toolchain,
     select_gcc_cpp_toolchain,
-    select_default_c_toolchain,
-    select_default_cpp_toolchain,
     RootRule(NativeToolchain),
   ]
diff --git a/src/python/pants/backend/native/tasks/c_compile.py b/src/python/pants/backend/native/tasks/c_compile.py
index 6f9471f971c1..d962687a9574 100644
--- a/src/python/pants/backend/native/tasks/c_compile.py
+++ b/src/python/pants/backend/native/tasks/c_compile.py
@@ -4,7 +4,7 @@
 
 from __future__ import absolute_import, division, print_function, unicode_literals
 
-from pants.backend.native.config.environment import CToolchain
+from pants.backend.native.config.environment import LLVMCToolchain
 from pants.backend.native.subsystems.native_compile_settings import CCompileSettings
 from pants.backend.native.subsystems.native_toolchain import NativeToolchain
 from pants.backend.native.targets.native_library import CLibrary
@@ -40,7 +40,7 @@ def get_compile_settings(self):
 
   @memoized_property
   def _c_toolchain(self):
-    return self._request_single(CToolchain, self._native_toolchain)
+    return self._request_single(LLVMCToolchain, self._native_toolchain).c_toolchain
 
   def get_compiler(self):
     return self._c_toolchain.c_compiler
diff --git a/src/python/pants/backend/native/tasks/cpp_compile.py b/src/python/pants/backend/native/tasks/cpp_compile.py
index 33aef5bfc249..322c62432c26 100644
--- a/src/python/pants/backend/native/tasks/cpp_compile.py
+++ b/src/python/pants/backend/native/tasks/cpp_compile.py
@@ -4,7 +4,7 @@
 
 from __future__ import absolute_import, division, print_function, unicode_literals
 
-from pants.backend.native.config.environment import CppToolchain
+from pants.backend.native.config.environment import LLVMCppToolchain
 from pants.backend.native.subsystems.native_compile_settings import CppCompileSettings
 from pants.backend.native.subsystems.native_toolchain import NativeToolchain
 from pants.backend.native.targets.native_library import CppLibrary
@@ -40,7 +40,7 @@ def get_compile_settings(self):
 
   @memoized_property
   def _cpp_toolchain(self):
-    return self._request_single(CppToolchain, self._native_toolchain)
+    return self._request_single(LLVMCppToolchain, self._native_toolchain).cpp_toolchain
 
   def get_compiler(self):
     return self._cpp_toolchain.cpp_compiler