Add make lint command. Make Go code golint clean.

Makefile

@@ -81,7 +81,7 @@ watch:
 	-@$(MAKE) test
 	@while inotifywait -q -e modify --exclude '^\./(build|\.git)/' --recursive .; do sleep 0.2; $(MAKE) test; done
 
-.PHONY: all benchmarks clean cover run test watch
+.PHONY: all benchmarks clean cover lint run test watch
 
 # ------------------------------------------------------------------------------
 # grumpc compiler
@@ -140,6 +140,12 @@ $(RUNTIME_COVER_FILE): $(RUNTIME) $(filter %_test.go,$(RUNTIME_SRCS))
 cover: $(RUNTIME_COVER_FILE) $(TOOL_BINS)
 	@bash -c 'comm -12 <(coverparse $< | sed "s/^grumpy/runtime/" | sort) <(git diff --dst-prefix= $(DIFF_COMMIT) | diffrange | sort)' | sort -t':' -k1,1 -k2n,2 | sed 's/$$/: missing coverage/' | tee errors.err
 
+build/bin/golint:
+	@go get -u github.com/golang/lint/golint
+
+lint: build/bin/golint
+	@golint runtime
+
 # ------------------------------------------------------------------------------
 # Standard library
 # ------------------------------------------------------------------------------

runtime/code.go

@@ -8,13 +8,17 @@ import (
 // CodeType is the object representing the Python 'code' type.
 var CodeType = newBasisType("code", reflect.TypeOf(Code{}), toCodeUnsafe, ObjectType)
 
+// CodeFlag is a switch controlling the behavior of a Code object.
 type CodeFlag int
 
 const (
+	// CodeFlagVarArg means a Code object accepts *arg parameters.
 	CodeFlagVarArg CodeFlag = 4
-	CodeFlagKWArg  CodeFlag = 8
+	// CodeFlagKWArg means a Code object accepts **kwarg parameters.
+	CodeFlagKWArg CodeFlag = 8
 )
 
+// Code represents Python 'code' objects.
 type Code struct {
 	Object
 	name     string `attr:"co_name"`
@@ -29,6 +33,7 @@ type Code struct {
 	fn      func(*Frame, []*Object) (*Object, *BaseException)
 }
 
+// NewCode creates a new Code object that executes the given fn.
 func NewCode(name, filename string, args []FunctionArg, flags CodeFlag, fn func(*Frame, []*Object) (*Object, *BaseException)) *Code {
 	argc := len(args)
 	minArgc := 0
@@ -50,7 +55,9 @@ func toCodeUnsafe(o *Object) *Code {
 	return (*Code)(o.toPointer())
 }
 
+// Eval runs the code object c in the context of the given globals.
 func (c *Code) Eval(f *Frame, globals *Dict, args Args, kwargs KWArgs) (*Object, *BaseException) {
+	// Validate parameters.
 	argc := len(args)
 	if argc > c.argc && c.flags&CodeFlagVarArg == 0 {
 		format := "%s() takes %d arguments (%d given)"