Add staticcheck tool

vendor/honnef.co/go/tools/staticcheck/sa6002/sa6002.go

@@ -0,0 +1,52 @@
+package sa6002
+
+import (
+	"go/types"
+
+	"honnef.co/go/tools/analysis/callcheck"
+	"honnef.co/go/tools/analysis/lint"
+	"honnef.co/go/tools/go/types/typeutil"
+	"honnef.co/go/tools/internal/passes/buildir"
+	"honnef.co/go/tools/knowledge"
+
+	"golang.org/x/tools/go/analysis"
+)
+
+var SCAnalyzer = lint.InitializeAnalyzer(&lint.Analyzer{
+	Analyzer: &analysis.Analyzer{
+		Name:     "SA6002",
+		Requires: []*analysis.Analyzer{buildir.Analyzer},
+		Run:      callcheck.Analyzer(rules),
+	},
+	Doc: &lint.RawDocumentation{
+		Title: `Storing non-pointer values in \'sync.Pool\' allocates memory`,
+		Text: `A \'sync.Pool\' is used to avoid unnecessary allocations and reduce the
+amount of work the garbage collector has to do.
+
+When passing a value that is not a pointer to a function that accepts
+an interface, the value needs to be placed on the heap, which means an
+additional allocation. Slices are a common thing to put in sync.Pools,
+and they're structs with 3 fields (length, capacity, and a pointer to
+an array). In order to avoid the extra allocation, one should store a
+pointer to the slice instead.
+
+See the comments on https://go-review.googlesource.com/c/go/+/24371
+that discuss this problem.`,
+		Since:    "2017.1",
+		Severity: lint.SeverityWarning,
+		MergeIf:  lint.MergeIfAny,
+	},
+})
+
+var Analyzer = SCAnalyzer.Analyzer
+
+var rules = map[string]callcheck.Check{
+	"(*sync.Pool).Put": func(call *callcheck.Call) {
+		arg := call.Args[knowledge.Arg("(*sync.Pool).Put.x")]
+		typ := arg.Value.Value.Type()
+		_, isSlice := typ.Underlying().(*types.Slice)
+		if !typeutil.IsPointerLike(typ) || isSlice {
+			arg.Invalid("argument should be pointer-like to avoid allocations")
+		}
+	},
+}