Add staticcheck tool

vendor/honnef.co/go/tools/staticcheck/sa4015/sa4015.go

@@ -0,0 +1,56 @@
+package sa4015
+
+import (
+	"fmt"
+	"go/types"
+
+	"honnef.co/go/tools/analysis/callcheck"
+	"honnef.co/go/tools/analysis/lint"
+	"honnef.co/go/tools/go/ir"
+	"honnef.co/go/tools/go/ir/irutil"
+	"honnef.co/go/tools/go/types/typeutil"
+	"honnef.co/go/tools/internal/passes/buildir"
+
+	"golang.org/x/tools/go/analysis"
+)
+
+var SCAnalyzer = lint.InitializeAnalyzer(&lint.Analyzer{
+	Analyzer: &analysis.Analyzer{
+		Name:     "SA4015",
+		Requires: []*analysis.Analyzer{buildir.Analyzer},
+		Run:      callcheck.Analyzer(checkMathIntRules),
+	},
+	Doc: &lint.RawDocumentation{
+		Title:    `Calling functions like \'math.Ceil\' on floats converted from integers doesn't do anything useful`,
+		Since:    "2017.1",
+		Severity: lint.SeverityWarning,
+		MergeIf:  lint.MergeIfAll,
+	},
+})
+
+var Analyzer = SCAnalyzer.Analyzer
+
+var checkMathIntRules = map[string]callcheck.Check{
+	"math.Ceil":  pointlessIntMath,
+	"math.Floor": pointlessIntMath,
+	"math.IsNaN": pointlessIntMath,
+	"math.Trunc": pointlessIntMath,
+	"math.IsInf": pointlessIntMath,
+}
+
+func pointlessIntMath(call *callcheck.Call) {
+	if ConvertedFromInt(call.Args[0].Value) {
+		call.Invalid(fmt.Sprintf("calling %s on a converted integer is pointless", irutil.CallName(call.Instr.Common())))
+	}
+}
+
+func ConvertedFromInt(v callcheck.Value) bool {
+	conv, ok := v.Value.(*ir.Convert)
+	if !ok {
+		return false
+	}
+	return typeutil.NewTypeSet(conv.X.Type()).All(func(t *types.Term) bool {
+		b, ok := t.Type().Underlying().(*types.Basic)
+		return ok && b.Info()&types.IsInteger != 0
+	})
+}