python3Packages.mypy: compile with mypyc

Mypy includes mypyc, a compiler that translates annotated Python to C,
which can be compiled into a Python module. When mypy is compiled with
mypyc, it is about 4 times faster than the interpreted mypy, so using
the compiled version is especially useful on large codebases where
typechecking may take a long time.

The wheels distributed on Pypi have included a mypyc-compiled mypy by
default since version 0.700 [1].

[1]: http://mypy-lang.blogspot.com/2019/04/mypy-0700-released-up-to-4x-faster.html

pkgs/development/python-modules/mypy/default.nix

@@ -1,16 +1,22 @@
-{ stdenv, fetchPypi, buildPythonPackage, typed-ast, psutil, isPy3k
+{ stdenv, fetchFromGitHub, buildPythonPackage, typed-ast, psutil, isPy3k
 , mypy-extensions
 , typing-extensions
+, fetchpatch
 }:
-
 buildPythonPackage rec {
   pname = "mypy";
   version = "0.790";
   disabled = !isPy3k;
 
-  src = fetchPypi {
-    inherit pname version;
-    sha256 = "sha256-KyG6Ra2e8uLriM5K6t0BEtD1AmQYMkF2/UlKaCS3SXU=";
+  # Fetch 0.790 from GitHub temporarily because mypyc.analysis is missing from
+  # the Pip package (see also https://github.com/python/mypy/issues/9584). It
+  # should be possible to move back to Pypi for the next release.
+  src = fetchFromGitHub {
+    owner = "python";
+    repo = pname;
+    rev = "v${version}";
+    sha256 = "0zq3lpdf9hphcklk40wz444h8w3dkhwa12mqba5j9lmg11klnhz7";
+    fetchSubmodules = true;
   };
 
   propagatedBuildInputs = [ typed-ast psutil mypy-extensions typing-extensions ];
@@ -24,8 +30,31 @@ buildPythonPackage rec {
     "mypy.api"
     "mypy.fastparse"
     "mypy.report"
+    "mypyc"
+    "mypyc.analysis"
+  ];
+
+  # These three patches are required to make compilation with mypyc work for
+  # 0.790, see also https://github.com/python/mypy/issues/9584.
+  patches = [
+    (fetchpatch {
+      url = "https://github.com/python/mypy/commit/f6522ae646a8d87ce10549f29fcf961dc014f154.patch";
+      sha256 = "0d3jp4d0b7vdc0prk07grhajsy7x3wcynn2xysnszawiww93bfrh";
+    })
+    (fetchpatch {
+      url = "https://github.com/python/mypy/commit/acd603496237a78b109ca9d89991539633cbbb99.patch";
+      sha256 = "0ry1rxpz2ws7zzrmq09pra9dlzxb84zhs8kxwf5xii1k1bgmrljr";
+    })
+    (fetchpatch {
+      url = "https://github.com/python/mypy/commit/81818b23b5d53f31caf3515d6f0b54e3c018d790.patch";
+      sha256 = "002y24kfscywkw4mz9lndsps543j4xhr2kcnfbrqr4i0yxlvdbca";
+    })
   ];
 
+  # Compile mypy with mypyc, which makes mypy about 4 times faster. The compiled
+  # version is also the default in the wheels on Pypi that include binaries.
+  MYPY_USE_MYPYC = "1";
+
   meta = with stdenv.lib; {
     description = "Optional static typing for Python";
     homepage    = "http://www.mypy-lang.org";