Add some type annotations and fix lints

Some things, like `method[...](...)` or `x: ... = ...` python 3.5
doesn't support, so I made a comment instead with the intention that it
can someday be made into a real annotation.

8 files changed, 20 insertions, 21 deletions

diff --git a/mesonbuild/build.py b/mesonbuild/build.py
index 5248d97..4c8e50b 100644
--- a/mesonbuild/build.py
+++ b/mesonbuild/build.py
@@ -28,7 +28,7 @@ from .mesonlib import (
     get_filenames_templates_dict, substitute_values,
     for_windows, for_darwin, for_cygwin, for_android, has_path_sep
 )
-from .compilers import is_object, clink_langs, sort_clink, lang_suffixes, get_macos_dylib_install_name
+from .compilers import Compiler, is_object, clink_langs, sort_clink, lang_suffixes, get_macos_dylib_install_name
 from .interpreterbase import FeatureNew
 
 pch_kwargs = set(['c_pch', 'cpp_pch'])
@@ -450,7 +450,7 @@ class BuildTarget(Target):
         self.is_unity = unity_opt == 'on' or (unity_opt == 'subprojects' and subproject != '')
         self.environment = environment
         self.sources = []
-        self.compilers = OrderedDict()
+        self.compilers = OrderedDict() # type: OrderedDict[str, Compiler]
         self.objects = []
         self.external_deps = []
         self.include_dirs = []
diff --git a/mesonbuild/compilers/cpp.py b/mesonbuild/compilers/cpp.py
index 7c2253d..2b2c4a0 100644
--- a/mesonbuild/compilers/cpp.py
+++ b/mesonbuild/compilers/cpp.py
@@ -23,7 +23,6 @@ from .c import CCompiler, VisualStudioCCompiler, ClangClCCompiler, IntelClCCompi
 from .compilers import (
     gnu_winlibs,
     msvc_winlibs,
-    CompilerType,
     ClangCompiler,
     GnuCompiler,
     ElbrusCompiler,
diff --git a/mesonbuild/coredata.py b/mesonbuild/coredata.py
index 9281019..b836086 100644
--- a/mesonbuild/coredata.py
+++ b/mesonbuild/coredata.py
@@ -20,7 +20,7 @@ from pathlib import PurePath
 from collections import OrderedDict
 from .mesonlib import (
     MesonException, MachineChoice, PerMachine,
-    default_libdir, default_libexecdir, default_prefix, stringlistify
+    default_libdir, default_libexecdir, default_prefix
 )
 from .wrap import WrapMode
 import ast
diff --git a/mesonbuild/dependencies/base.py b/mesonbuild/dependencies/base.py
index 6063fd3..1a60a16 100644
--- a/mesonbuild/dependencies/base.py
+++ b/mesonbuild/dependencies/base.py
@@ -14,7 +14,6 @@
 
 # This file contains the detection logic for external dependencies.
 # Custom logic for several other packages are in separate files.
-from typing import Dict, Any
 import copy
 import functools
 import os
@@ -26,7 +25,7 @@ import textwrap
 import platform
 import itertools
 import ctypes
-from typing import List, Tuple
+from typing import Any, Dict, List, Tuple
 from enum import Enum
 from pathlib import Path, PurePath
 
@@ -2302,7 +2301,7 @@ class ExtraFrameworkDependency(ExternalDependency):
         return 'framework'
 
 
-def get_dep_identifier(name, kwargs, want_cross):
+def get_dep_identifier(name, kwargs, want_cross: bool) -> Tuple:
     identifier = (name, want_cross)
     for key, value in kwargs.items():
         # 'version' is irrelevant for caching; the caller must check version matches
diff --git a/mesonbuild/envconfig.py b/mesonbuild/envconfig.py
index f4c371f..977d930 100644
--- a/mesonbuild/envconfig.py
+++ b/mesonbuild/envconfig.py
@@ -255,7 +255,7 @@ class MachineInfo:
     def libdir_layout_is_win(self) -> bool:
         return self.is_windows() or self.is_cygwin()
 
-class PerMachineDefaultable(PerMachine[_T]):
+class PerMachineDefaultable(PerMachine[typing.Optional[_T]]):
     """Extends `PerMachine` with the ability to default from `None`s.
     """
     def __init__(self) -> None:
@@ -285,7 +285,7 @@ class PerMachineDefaultable(PerMachine[_T]):
         if self.host == self.build:
             self.host = None
 
-class MachineInfos(PerMachineDefaultable[typing.Optional[MachineInfo]]):
+class MachineInfos(PerMachineDefaultable[MachineInfo]):
     def matches_build_machine(self, machine: MachineChoice) -> bool:
         return self.build == self[machine]
 
diff --git a/mesonbuild/environment.py b/mesonbuild/environment.py
index bf2cce9..462672e 100644
--- a/mesonbuild/environment.py
+++ b/mesonbuild/environment.py
@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-import os, platform, re, sys, shlex, shutil, subprocess
+import os, platform, re, sys, shlex, shutil, subprocess, typing
 
 from . import coredata
 from .linkers import ArLinker, ArmarLinker, VisualStudioLinker, DLinker, CcrxLinker
@@ -28,6 +28,7 @@ from .envconfig import (
 )
 from . import compilers
 from .compilers import (
+    Compiler,
     CompilerType,
     is_assembly,
     is_header,
@@ -83,6 +84,8 @@ from .compilers import (
 
 build_filename = 'meson.build'
 
+CompilersDict = typing.Dict[str, Compiler]
+
 def detect_gcovr(min_version='3.3', new_rootdir_version='4.2', log=False):
     gcovr_exe = 'gcovr'
     try:
@@ -150,7 +153,7 @@ def detect_native_windows_arch():
             raise EnvironmentException('Unable to detect native OS architecture')
     return arch
 
-def detect_windows_arch(compilers):
+def detect_windows_arch(compilers: CompilersDict) -> str:
     """
     Detecting the 'native' architecture of Windows is not a trivial task. We
     cannot trust that the architecture that Python is built for is the 'native'
@@ -190,7 +193,7 @@ def detect_windows_arch(compilers):
             return 'x86'
     return os_arch
 
-def any_compiler_has_define(compilers, define):
+def any_compiler_has_define(compilers: CompilersDict, define):
     for c in compilers.values():
         try:
             if c.has_builtin_define(define):
@@ -200,7 +203,7 @@ def any_compiler_has_define(compilers, define):
             pass
     return False
 
-def detect_cpu_family(compilers):
+def detect_cpu_family(compilers: CompilersDict) -> str:
     """
     Python is inconsistent in its platform module.
     It returns different values for the same cpu.
@@ -262,7 +265,7 @@ def detect_cpu_family(compilers):
 
     return trial
 
-def detect_cpu(compilers):
+def detect_cpu(compilers: CompilersDict):
     if mesonlib.is_windows():
         trial = detect_windows_arch(compilers)
     else:
@@ -295,7 +298,7 @@ def detect_msys2_arch():
         return os.environ['MSYSTEM_CARCH']
     return None
 
-def detect_machine_info(compilers = None) -> MachineInfo:
+def detect_machine_info(compilers: typing.Optional[CompilersDict] = None) -> MachineInfo:
     """Detect the machine we're running on
 
     If compilers are not provided, we cannot know as much. None out those
diff --git a/mesonbuild/mesonlib.py b/mesonbuild/mesonlib.py
index e389fb1..1e776e4 100644
--- a/mesonbuild/mesonlib.py
+++ b/mesonbuild/mesonlib.py
@@ -323,22 +323,20 @@ class MachineChoice(OrderedEnum):
     HOST = 1
     TARGET = 2
 
-_T = typing.TypeVar('_T')
-
 class PerMachine(typing.Generic[_T]):
-    def __init__(self, build: typing.Optional[_T], host: typing.Optional[_T], target: typing.Optional[_T]):
+    def __init__(self, build: _T, host: _T, target: _T):
         self.build = build
         self.host = host
         self.target = target
 
-    def __getitem__(self, machine: MachineChoice) -> typing.Optional[_T]:
+    def __getitem__(self, machine: MachineChoice) -> _T:
         return {
             MachineChoice.BUILD:  self.build,
             MachineChoice.HOST:   self.host,
             MachineChoice.TARGET: self.target
         }[machine]
 
-    def __setitem__(self, machine: MachineChoice, val: typing.Optional[_T]) -> None:
+    def __setitem__(self, machine: MachineChoice, val: _T) -> None:
         key = {
             MachineChoice.BUILD:  'build',
             MachineChoice.HOST:   'host',
diff --git a/mesonbuild/mintro.py b/mesonbuild/mintro.py
index a4a6978..c47fffd 100644
--- a/mesonbuild/mintro.py
+++ b/mesonbuild/mintro.py
@@ -27,7 +27,7 @@ from . import mlog
 from .backend import backends
 from .mparser import FunctionNode, ArrayNode, ArgumentNode, StringNode
 from typing import List, Optional
-import sys, os
+import os
 import pathlib
 
 def get_meson_info_file(info_dir: str):