X-Git-Url: https://git.josue.xyz/?p=dotfiles%2F.git;a=blobdiff_plain;f=.config%2Fcoc%2Fextensions%2Fcoc-go-data%2Ftools%2Fpkg%2Fmod%2Fhonnef.co%2Fgo%2Ftools%40v0.1.1%2Fsimple%2Flint.go;fp=.config%2Fcoc%2Fextensions%2Fcoc-go-data%2Ftools%2Fpkg%2Fmod%2Fhonnef.co%2Fgo%2Ftools%40v0.1.1%2Fsimple%2Flint.go;h=08c67cccb2c3ca9b3bd6af4f8024074b0cfeb407;hp=0000000000000000000000000000000000000000;hb=3c06164f15bd10aed7d66b6314764a2961a14762;hpb=0e9c3ceb40901f4d44981c1376cb9e23a248e006

diff --git a/.config/coc/extensions/coc-go-data/tools/pkg/mod/honnef.co/go/tools@v0.1.1/simple/lint.go b/.config/coc/extensions/coc-go-data/tools/pkg/mod/honnef.co/go/tools@v0.1.1/simple/lint.go
new file mode 100644
index 00000000..08c67ccc
--- /dev/null
+++ b/.config/coc/extensions/coc-go-data/tools/pkg/mod/honnef.co/go/tools@v0.1.1/simple/lint.go
@@ -0,0 +1,1904 @@
+// Package simple contains a linter for Go source code.
+package simple
+
+import (
+	"fmt"
+	"go/ast"
+	"go/constant"
+	"go/token"
+	"go/types"
+	"path/filepath"
+	"reflect"
+	"sort"
+	"strings"
+
+	"honnef.co/go/tools/analysis/code"
+	"honnef.co/go/tools/analysis/edit"
+	"honnef.co/go/tools/analysis/lint"
+	"honnef.co/go/tools/analysis/report"
+	"honnef.co/go/tools/go/ast/astutil"
+	"honnef.co/go/tools/go/types/typeutil"
+	"honnef.co/go/tools/internal/passes/buildir"
+	"honnef.co/go/tools/internal/sharedcheck"
+	"honnef.co/go/tools/knowledge"
+	"honnef.co/go/tools/pattern"
+
+	"golang.org/x/tools/go/analysis"
+	gotypeutil "golang.org/x/tools/go/types/typeutil"
+)
+
+var (
+	checkSingleCaseSelectQ1 = pattern.MustParse(`
+		(ForStmt
+			nil nil nil
+			select@(SelectStmt
+				(CommClause
+					(Or
+						(UnaryExpr "<-" _)
+						(AssignStmt _ _ (UnaryExpr "<-" _)))
+					_)))`)
+	checkSingleCaseSelectQ2 = pattern.MustParse(`(SelectStmt (CommClause _ _))`)
+)
+
+func CheckSingleCaseSelect(pass *analysis.Pass) (interface{}, error) {
+	seen := map[ast.Node]struct{}{}
+	fn := func(node ast.Node) {
+		if m, ok := code.Match(pass, checkSingleCaseSelectQ1, node); ok {
+			seen[m.State["select"].(ast.Node)] = struct{}{}
+			report.Report(pass, node, "should use for range instead of for { select {} }", report.FilterGenerated())
+		} else if _, ok := code.Match(pass, checkSingleCaseSelectQ2, node); ok {
+			if _, ok := seen[node]; !ok {
+				report.Report(pass, node, "should use a simple channel send/receive instead of select with a single case",
+					report.ShortRange(),
+					report.FilterGenerated())
+			}
+		}
+	}
+	code.Preorder(pass, fn, (*ast.ForStmt)(nil), (*ast.SelectStmt)(nil))
+	return nil, nil
+}
+
+var (
+	checkLoopCopyQ = pattern.MustParse(`
+		(Or
+			(RangeStmt
+				key value ":=" src@(Ident _)
+				[(AssignStmt
+					(IndexExpr dst@(Ident _) key)
+					"="
+					value)])
+			(RangeStmt
+				key nil ":=" src@(Ident _)
+				[(AssignStmt
+					(IndexExpr dst@(Ident _) key)
+					"="
+					(IndexExpr src key))]))`)
+	checkLoopCopyR = pattern.MustParse(`(CallExpr (Ident "copy") [dst src])`)
+)
+
+func CheckLoopCopy(pass *analysis.Pass) (interface{}, error) {
+	fn := func(node ast.Node) {
+		m, edits, ok := code.MatchAndEdit(pass, checkLoopCopyQ, checkLoopCopyR, node)
+		if !ok {
+			return
+		}
+		t1 := pass.TypesInfo.TypeOf(m.State["src"].(*ast.Ident))
+		t2 := pass.TypesInfo.TypeOf(m.State["dst"].(*ast.Ident))
+		if _, ok := t1.Underlying().(*types.Slice); !ok {
+			return
+		}
+		if !types.Identical(t1, t2) {
+			return
+		}
+
+		tv, err := types.Eval(pass.Fset, pass.Pkg, node.Pos(), "copy")
+		if err == nil && tv.IsBuiltin() {
+			report.Report(pass, node,
+				"should use copy() instead of a loop",
+				report.ShortRange(),
+				report.FilterGenerated(),
+				report.Fixes(edit.Fix("replace loop with call to copy()", edits...)))
+		} else {
+			report.Report(pass, node, "should use copy() instead of a loop", report.FilterGenerated())
+		}
+	}
+	code.Preorder(pass, fn, (*ast.RangeStmt)(nil))
+	return nil, nil
+}
+
+func CheckIfBoolCmp(pass *analysis.Pass) (interface{}, error) {
+	fn := func(node ast.Node) {
+		if code.IsInTest(pass, node) {
+			return
+		}
+
+		expr := node.(*ast.BinaryExpr)
+		if expr.Op != token.EQL && expr.Op != token.NEQ {
+			return
+		}
+		x := code.IsBoolConst(pass, expr.X)
+		y := code.IsBoolConst(pass, expr.Y)
+		if !x && !y {
+			return
+		}
+		var other ast.Expr
+		var val bool
+		if x {
+			val = code.BoolConst(pass, expr.X)
+			other = expr.Y
+		} else {
+			val = code.BoolConst(pass, expr.Y)
+			other = expr.X
+		}
+		basic, ok := pass.TypesInfo.TypeOf(other).Underlying().(*types.Basic)
+		if !ok || basic.Kind() != types.Bool {
+			return
+		}
+		op := ""
+		if (expr.Op == token.EQL && !val) || (expr.Op == token.NEQ && val) {
+			op = "!"
+		}
+		r := op + report.Render(pass, other)
+		l1 := len(r)
+		r = strings.TrimLeft(r, "!")
+		if (l1-len(r))%2 == 1 {
+			r = "!" + r
+		}
+		report.Report(pass, expr, fmt.Sprintf("should omit comparison to bool constant, can be simplified to %s", r),
+			report.FilterGenerated(),
+			report.Fixes(edit.Fix("simplify bool comparison", edit.ReplaceWithString(pass.Fset, expr, r))))
+	}
+	code.Preorder(pass, fn, (*ast.BinaryExpr)(nil))
+	return nil, nil
+}
+
+var (
+	checkBytesBufferConversionsQ  = pattern.MustParse(`(CallExpr _ [(CallExpr sel@(SelectorExpr recv _) [])])`)
+	checkBytesBufferConversionsRs = pattern.MustParse(`(CallExpr (SelectorExpr recv (Ident "String")) [])`)
+	checkBytesBufferConversionsRb = pattern.MustParse(`(CallExpr (SelectorExpr recv (Ident "Bytes")) [])`)
+)
+
+func CheckBytesBufferConversions(pass *analysis.Pass) (interface{}, error) {
+	if pass.Pkg.Path() == "bytes" || pass.Pkg.Path() == "bytes_test" {
+		// The bytes package can use itself however it wants
+		return nil, nil
+	}
+	fn := func(node ast.Node, stack []ast.Node) {
+		m, ok := code.Match(pass, checkBytesBufferConversionsQ, node)
+		if !ok {
+			return
+		}
+		call := node.(*ast.CallExpr)
+		sel := m.State["sel"].(*ast.SelectorExpr)
+
+		typ := pass.TypesInfo.TypeOf(call.Fun)
+		if typ == types.Universe.Lookup("string").Type() && code.IsCallTo(pass, call.Args[0], "(*bytes.Buffer).Bytes") {
+			if _, ok := stack[len(stack)-2].(*ast.IndexExpr); ok {
+				// Don't flag m[string(buf.Bytes())] – thanks to a
+				// compiler optimization, this is actually faster than
+				// m[buf.String()]
+				return
+			}
+
+			report.Report(pass, call, fmt.Sprintf("should use %v.String() instead of %v", report.Render(pass, sel.X), report.Render(pass, call)),
+				report.FilterGenerated(),
+				report.Fixes(edit.Fix("simplify conversion", edit.ReplaceWithPattern(pass, checkBytesBufferConversionsRs, m.State, node))))
+		} else if typ, ok := typ.(*types.Slice); ok && typ.Elem() == types.Universe.Lookup("byte").Type() && code.IsCallTo(pass, call.Args[0], "(*bytes.Buffer).String") {
+			report.Report(pass, call, fmt.Sprintf("should use %v.Bytes() instead of %v", report.Render(pass, sel.X), report.Render(pass, call)),
+				report.FilterGenerated(),
+				report.Fixes(edit.Fix("simplify conversion", edit.ReplaceWithPattern(pass, checkBytesBufferConversionsRb, m.State, node))))
+		}
+
+	}
+	code.PreorderStack(pass, fn, (*ast.CallExpr)(nil))
+	return nil, nil
+}
+
+func CheckStringsContains(pass *analysis.Pass) (interface{}, error) {
+	// map of value to token to bool value
+	allowed := map[int64]map[token.Token]bool{
+		-1: {token.GTR: true, token.NEQ: true, token.EQL: false},
+		0:  {token.GEQ: true, token.LSS: false},
+	}
+	fn := func(node ast.Node) {
+		expr := node.(*ast.BinaryExpr)
+		switch expr.Op {
+		case token.GEQ, token.GTR, token.NEQ, token.LSS, token.EQL:
+		default:
+			return
+		}
+
+		value, ok := code.ExprToInt(pass, expr.Y)
+		if !ok {
+			return
+		}
+
+		allowedOps, ok := allowed[value]
+		if !ok {
+			return
+		}
+		b, ok := allowedOps[expr.Op]
+		if !ok {
+			return
+		}
+
+		call, ok := expr.X.(*ast.CallExpr)
+		if !ok {
+			return
+		}
+		sel, ok := call.Fun.(*ast.SelectorExpr)
+		if !ok {
+			return
+		}
+		pkgIdent, ok := sel.X.(*ast.Ident)
+		if !ok {
+			return
+		}
+		funIdent := sel.Sel
+		if pkgIdent.Name != "strings" && pkgIdent.Name != "bytes" {
+			return
+		}
+
+		var r ast.Expr
+		switch funIdent.Name {
+		case "IndexRune":
+			r = &ast.SelectorExpr{
+				X:   pkgIdent,
+				Sel: &ast.Ident{Name: "ContainsRune"},
+			}
+		case "IndexAny":
+			r = &ast.SelectorExpr{
+				X:   pkgIdent,
+				Sel: &ast.Ident{Name: "ContainsAny"},
+			}
+		case "Index":
+			r = &ast.SelectorExpr{
+				X:   pkgIdent,
+				Sel: &ast.Ident{Name: "Contains"},
+			}
+		default:
+			return
+		}
+
+		r = &ast.CallExpr{
+			Fun:  r,
+			Args: call.Args,
+		}
+		if !b {
+			r = &ast.UnaryExpr{
+				Op: token.NOT,
+				X:  r,
+			}
+		}
+
+		report.Report(pass, node, fmt.Sprintf("should use %s instead", report.Render(pass, r)),
+			report.FilterGenerated(),
+			report.Fixes(edit.Fix(fmt.Sprintf("simplify use of %s", report.Render(pass, call.Fun)), edit.ReplaceWithNode(pass.Fset, node, r))))
+	}
+	code.Preorder(pass, fn, (*ast.BinaryExpr)(nil))
+	return nil, nil
+}
+
+var (
+	checkBytesCompareQ  = pattern.MustParse(`(BinaryExpr (CallExpr (Function "bytes.Compare") args) op@(Or "==" "!=") (BasicLit "INT" "0"))`)
+	checkBytesCompareRe = pattern.MustParse(`(CallExpr (SelectorExpr (Ident "bytes") (Ident "Equal")) args)`)
+	checkBytesCompareRn = pattern.MustParse(`(UnaryExpr "!" (CallExpr (SelectorExpr (Ident "bytes") (Ident "Equal")) args))`)
+)
+
+func CheckBytesCompare(pass *analysis.Pass) (interface{}, error) {
+	if pass.Pkg.Path() == "bytes" || pass.Pkg.Path() == "bytes_test" {
+		// the bytes package is free to use bytes.Compare as it sees fit
+		return nil, nil
+	}
+	fn := func(node ast.Node) {
+		m, ok := code.Match(pass, checkBytesCompareQ, node)
+		if !ok {
+			return
+		}
+
+		args := report.RenderArgs(pass, m.State["args"].([]ast.Expr))
+		prefix := ""
+		if m.State["op"].(token.Token) == token.NEQ {
+			prefix = "!"
+		}
+
+		var fix analysis.SuggestedFix
+		switch tok := m.State["op"].(token.Token); tok {
+		case token.EQL:
+			fix = edit.Fix("simplify use of bytes.Compare", edit.ReplaceWithPattern(pass, checkBytesCompareRe, m.State, node))
+		case token.NEQ:
+			fix = edit.Fix("simplify use of bytes.Compare", edit.ReplaceWithPattern(pass, checkBytesCompareRn, m.State, node))
+		default:
+			panic(fmt.Sprintf("unexpected token %v", tok))
+		}
+		report.Report(pass, node, fmt.Sprintf("should use %sbytes.Equal(%s) instead", prefix, args), report.FilterGenerated(), report.Fixes(fix))
+	}
+	code.Preorder(pass, fn, (*ast.BinaryExpr)(nil))
+	return nil, nil
+}
+
+func CheckForTrue(pass *analysis.Pass) (interface{}, error) {
+	fn := func(node ast.Node) {
+		loop := node.(*ast.ForStmt)
+		if loop.Init != nil || loop.Post != nil {
+			return
+		}
+		if !code.IsBoolConst(pass, loop.Cond) || !code.BoolConst(pass, loop.Cond) {
+			return
+		}
+		report.Report(pass, loop, "should use for {} instead of for true {}",
+			report.ShortRange(),
+			report.FilterGenerated())
+	}
+	code.Preorder(pass, fn, (*ast.ForStmt)(nil))
+	return nil, nil
+}
+
+func CheckRegexpRaw(pass *analysis.Pass) (interface{}, error) {
+	fn := func(node ast.Node) {
+		call := node.(*ast.CallExpr)
+		if !code.IsCallToAny(pass, call, "regexp.MustCompile", "regexp.Compile") {
+			return
+		}
+		sel, ok := call.Fun.(*ast.SelectorExpr)
+		if !ok {
+			return
+		}
+		lit, ok := call.Args[knowledge.Arg("regexp.Compile.expr")].(*ast.BasicLit)
+		if !ok {
+			// TODO(dominikh): support string concat, maybe support constants
+			return
+		}
+		if lit.Kind != token.STRING {
+			// invalid function call
+			return
+		}
+		if lit.Value[0] != '"' {
+			// already a raw string
+			return
+		}
+		val := lit.Value
+		if !strings.Contains(val, `\\`) {
+			return
+		}
+		if strings.Contains(val, "`") {
+			return
+		}
+
+		bs := false
+		for _, c := range val {
+			if !bs && c == '\\' {
+				bs = true
+				continue
+			}
+			if bs && c == '\\' {
+				bs = false
+				continue
+			}
+			if bs {
+				// backslash followed by non-backslash -> escape sequence
+				return
+			}
+		}
+
+		report.Report(pass, call, fmt.Sprintf("should use raw string (`...`) with regexp.%s to avoid having to escape twice", sel.Sel.Name), report.FilterGenerated())
+	}
+	code.Preorder(pass, fn, (*ast.CallExpr)(nil))
+	return nil, nil
+}
+
+var (
+	checkIfReturnQIf  = pattern.MustParse(`(IfStmt nil cond [(ReturnStmt [ret@(Ident _)])] nil)`)
+	checkIfReturnQRet = pattern.MustParse(`(ReturnStmt [ret@(Ident _)])`)
+)
+
+func CheckIfReturn(pass *analysis.Pass) (interface{}, error) {
+	fn := func(node ast.Node) {
+		block := node.(*ast.BlockStmt)
+		l := len(block.List)
+		if l < 2 {
+			return
+		}
+		n1, n2 := block.List[l-2], block.List[l-1]
+
+		if len(block.List) >= 3 {
+			if _, ok := block.List[l-3].(*ast.IfStmt); ok {
+				// Do not flag a series of if statements
+				return
+			}
+		}
+		m1, ok := code.Match(pass, checkIfReturnQIf, n1)
+		if !ok {
+			return
+		}
+		m2, ok := code.Match(pass, checkIfReturnQRet, n2)
+		if !ok {
+			return
+		}
+
+		if op, ok := m1.State["cond"].(*ast.BinaryExpr); ok {
+			switch op.Op {
+			case token.EQL, token.LSS, token.GTR, token.NEQ, token.LEQ, token.GEQ:
+			default:
+				return
+			}
+		}
+
+		ret1 := m1.State["ret"].(*ast.Ident)
+		if !code.IsBoolConst(pass, ret1) {
+			return
+		}
+		ret2 := m2.State["ret"].(*ast.Ident)
+		if !code.IsBoolConst(pass, ret2) {
+			return
+		}
+
+		if ret1.Name == ret2.Name {
+			// we want the function to return true and false, not the
+			// same value both times.
+			return
+		}
+
+		cond := m1.State["cond"].(ast.Expr)
+		origCond := cond
+		if ret1.Name == "false" {
+			cond = negate(cond)
+		}
+		report.Report(pass, n1,
+			fmt.Sprintf("should use 'return %s' instead of 'if %s { return %s }; return %s'",
+				report.Render(pass, cond),
+				report.Render(pass, origCond), report.Render(pass, ret1), report.Render(pass, ret2)),
+			report.FilterGenerated())
+	}
+	code.Preorder(pass, fn, (*ast.BlockStmt)(nil))
+	return nil, nil
+}
+
+func negate(expr ast.Expr) ast.Expr {
+	switch expr := expr.(type) {
+	case *ast.BinaryExpr:
+		out := *expr
+		switch expr.Op {
+		case token.EQL:
+			out.Op = token.NEQ
+		case token.LSS:
+			out.Op = token.GEQ
+		case token.GTR:
+			out.Op = token.LEQ
+		case token.NEQ:
+			out.Op = token.EQL
+		case token.LEQ:
+			out.Op = token.GTR
+		case token.GEQ:
+			out.Op = token.LSS
+		}
+		return &out
+	case *ast.Ident, *ast.CallExpr, *ast.IndexExpr:
+		return &ast.UnaryExpr{
+			Op: token.NOT,
+			X:  expr,
+		}
+	default:
+		return &ast.UnaryExpr{
+			Op: token.NOT,
+			X: &ast.ParenExpr{
+				X: expr,
+			},
+		}
+	}
+}
+
+// CheckRedundantNilCheckWithLen checks for the following redundant nil-checks:
+//
+//   if x == nil || len(x) == 0 {}
+//   if x != nil && len(x) != 0 {}
+//   if x != nil && len(x) == N {} (where N != 0)
+//   if x != nil && len(x) > N {}
+//   if x != nil && len(x) >= N {} (where N != 0)
+//
+func CheckRedundantNilCheckWithLen(pass *analysis.Pass) (interface{}, error) {
+	isConstZero := func(expr ast.Expr) (isConst bool, isZero bool) {
+		_, ok := expr.(*ast.BasicLit)
+		if ok {
+			return true, astutil.IsIntLiteral(expr, "0")
+		}
+		id, ok := expr.(*ast.Ident)
+		if !ok {
+			return false, false
+		}
+		c, ok := pass.TypesInfo.ObjectOf(id).(*types.Const)
+		if !ok {
+			return false, false
+		}
+		return true, c.Val().Kind() == constant.Int && c.Val().String() == "0"
+	}
+
+	fn := func(node ast.Node) {
+		// check that expr is "x || y" or "x && y"
+		expr := node.(*ast.BinaryExpr)
+		if expr.Op != token.LOR && expr.Op != token.LAND {
+			return
+		}
+		eqNil := expr.Op == token.LOR
+
+		// check that x is "xx == nil" or "xx != nil"
+		x, ok := expr.X.(*ast.BinaryExpr)
+		if !ok {
+			return
+		}
+		if eqNil && x.Op != token.EQL {
+			return
+		}
+		if !eqNil && x.Op != token.NEQ {
+			return
+		}
+		xx, ok := x.X.(*ast.Ident)
+		if !ok {
+			return
+		}
+		if !code.IsNil(pass, x.Y) {
+			return
+		}
+
+		// check that y is "len(xx) == 0" or "len(xx) ... "
+		y, ok := expr.Y.(*ast.BinaryExpr)
+		if !ok {
+			return
+		}
+		if eqNil && y.Op != token.EQL { // must be len(xx) *==* 0
+			return
+		}
+		yx, ok := y.X.(*ast.CallExpr)
+		if !ok {
+			return
+		}
+		yxFun, ok := yx.Fun.(*ast.Ident)
+		if !ok || yxFun.Name != "len" || len(yx.Args) != 1 {
+			return
+		}
+		yxArg, ok := yx.Args[knowledge.Arg("len.v")].(*ast.Ident)
+		if !ok {
+			return
+		}
+		if yxArg.Name != xx.Name {
+			return
+		}
+
+		if eqNil && !astutil.IsIntLiteral(y.Y, "0") { // must be len(x) == *0*
+			return
+		}
+
+		if !eqNil {
+			isConst, isZero := isConstZero(y.Y)
+			if !isConst {
+				return
+			}
+			switch y.Op {
+			case token.EQL:
+				// avoid false positive for "xx != nil && len(xx) == 0"
+				if isZero {
+					return
+				}
+			case token.GEQ:
+				// avoid false positive for "xx != nil && len(xx) >= 0"
+				if isZero {
+					return
+				}
+			case token.NEQ:
+				// avoid false positive for "xx != nil && len(xx) != <non-zero>"
+				if !isZero {
+					return
+				}
+			case token.GTR:
+				// ok
+			default:
+				return
+			}
+		}
+
+		// finally check that xx type is one of array, slice, map or chan
+		// this is to prevent false positive in case if xx is a pointer to an array
+		var nilType string
+		switch pass.TypesInfo.TypeOf(xx).(type) {
+		case *types.Slice:
+			nilType = "nil slices"
+		case *types.Map:
+			nilType = "nil maps"
+		case *types.Chan:
+			nilType = "nil channels"
+		default:
+			return
+		}
+		report.Report(pass, expr, fmt.Sprintf("should omit nil check; len() for %s is defined as zero", nilType), report.FilterGenerated())
+	}
+	code.Preorder(pass, fn, (*ast.BinaryExpr)(nil))
+	return nil, nil
+}
+
+var checkSlicingQ = pattern.MustParse(`(SliceExpr x@(Object _) low (CallExpr (Builtin "len") [x]) nil)`)
+
+func CheckSlicing(pass *analysis.Pass) (interface{}, error) {
+	fn := func(node ast.Node) {
+		if _, ok := code.Match(pass, checkSlicingQ, node); ok {
+			expr := node.(*ast.SliceExpr)
+			report.Report(pass, expr.High,
+				"should omit second index in slice, s[a:len(s)] is identical to s[a:]",
+				report.FilterGenerated(),
+				report.Fixes(edit.Fix("simplify slice expression", edit.Delete(expr.High))))
+		}
+	}
+	code.Preorder(pass, fn, (*ast.SliceExpr)(nil))
+	return nil, nil
+}
+
+func refersTo(pass *analysis.Pass, expr ast.Expr, ident types.Object) bool {
+	found := false
+	fn := func(node ast.Node) bool {
+		ident2, ok := node.(*ast.Ident)
+		if !ok {
+			return true
+		}
+		if ident == pass.TypesInfo.ObjectOf(ident2) {
+			found = true
+			return false
+		}
+		return true
+	}
+	ast.Inspect(expr, fn)
+	return found
+}
+
+var checkLoopAppendQ = pattern.MustParse(`
+	(RangeStmt
+		(Ident "_")
+		val@(Object _)
+		_
+		x
+		[(AssignStmt [lhs] "=" [(CallExpr (Builtin "append") [lhs val])])]) `)
+
+func CheckLoopAppend(pass *analysis.Pass) (interface{}, error) {
+	fn := func(node ast.Node) {
+		m, ok := code.Match(pass, checkLoopAppendQ, node)
+		if !ok {
+			return
+		}
+
+		val := m.State["val"].(types.Object)
+		if refersTo(pass, m.State["lhs"].(ast.Expr), val) {
+			return
+		}
+
+		src := pass.TypesInfo.TypeOf(m.State["x"].(ast.Expr))
+		dst := pass.TypesInfo.TypeOf(m.State["lhs"].(ast.Expr))
+		if !types.Identical(src, dst) {
+			return
+		}
+
+		r := &ast.AssignStmt{
+			Lhs: []ast.Expr{m.State["lhs"].(ast.Expr)},
+			Tok: token.ASSIGN,
+			Rhs: []ast.Expr{
+				&ast.CallExpr{
+					Fun: &ast.Ident{Name: "append"},
+					Args: []ast.Expr{
+						m.State["lhs"].(ast.Expr),
+						m.State["x"].(ast.Expr),
+					},
+					Ellipsis: 1,
+				},
+			},
+		}
+
+		report.Report(pass, node, fmt.Sprintf("should replace loop with %s", report.Render(pass, r)),
+			report.ShortRange(),
+			report.FilterGenerated(),
+			report.Fixes(edit.Fix("replace loop with call to append", edit.ReplaceWithNode(pass.Fset, node, r))))
+	}
+	code.Preorder(pass, fn, (*ast.RangeStmt)(nil))
+	return nil, nil
+}
+
+var (
+	checkTimeSinceQ = pattern.MustParse(`(CallExpr (SelectorExpr (CallExpr (Function "time.Now") []) (Function "(time.Time).Sub")) [arg])`)
+	checkTimeSinceR = pattern.MustParse(`(CallExpr (SelectorExpr (Ident "time") (Ident "Since")) [arg])`)
+)
+
+func CheckTimeSince(pass *analysis.Pass) (interface{}, error) {
+	fn := func(node ast.Node) {
+		if _, edits, ok := code.MatchAndEdit(pass, checkTimeSinceQ, checkTimeSinceR, node); ok {
+			report.Report(pass, node, "should use time.Since instead of time.Now().Sub",
+				report.FilterGenerated(),
+				report.Fixes(edit.Fix("replace with call to time.Since", edits...)))
+		}
+	}
+	code.Preorder(pass, fn, (*ast.CallExpr)(nil))
+	return nil, nil
+}
+
+var (
+	checkTimeUntilQ = pattern.MustParse(`(CallExpr (Function "(time.Time).Sub") [(CallExpr (Function "time.Now") [])])`)
+	checkTimeUntilR = pattern.MustParse(`(CallExpr (SelectorExpr (Ident "time") (Ident "Until")) [arg])`)
+)
+
+func CheckTimeUntil(pass *analysis.Pass) (interface{}, error) {
+	if !code.IsGoVersion(pass, 8) {
+		return nil, nil
+	}
+	fn := func(node ast.Node) {
+		if _, ok := code.Match(pass, checkTimeUntilQ, node); ok {
+			if sel, ok := node.(*ast.CallExpr).Fun.(*ast.SelectorExpr); ok {
+				r := pattern.NodeToAST(checkTimeUntilR.Root, map[string]interface{}{"arg": sel.X}).(ast.Node)
+				report.Report(pass, node, "should use time.Until instead of t.Sub(time.Now())",
+					report.FilterGenerated(),
+					report.Fixes(edit.Fix("replace with call to time.Until", edit.ReplaceWithNode(pass.Fset, node, r))))
+			} else {
+				report.Report(pass, node, "should use time.Until instead of t.Sub(time.Now())", report.FilterGenerated())
+			}
+		}
+	}
+	code.Preorder(pass, fn, (*ast.CallExpr)(nil))
+	return nil, nil
+}
+
+var (
+	checkUnnecessaryBlankQ1 = pattern.MustParse(`
+		(AssignStmt
+			[_ (Ident "_")]
+			_
+			(Or
+				(IndexExpr _ _)
+				(UnaryExpr "<-" _))) `)
+	checkUnnecessaryBlankQ2 = pattern.MustParse(`
+		(AssignStmt
+			(Ident "_") _ recv@(UnaryExpr "<-" _))`)
+)
+
+func CheckUnnecessaryBlank(pass *analysis.Pass) (interface{}, error) {
+	fn1 := func(node ast.Node) {
+		if _, ok := code.Match(pass, checkUnnecessaryBlankQ1, node); ok {
+			r := *node.(*ast.AssignStmt)
+			r.Lhs = r.Lhs[0:1]
+			report.Report(pass, node, "unnecessary assignment to the blank identifier",
+				report.FilterGenerated(),
+				report.Fixes(edit.Fix("remove assignment to blank identifier", edit.ReplaceWithNode(pass.Fset, node, &r))))
+		} else if m, ok := code.Match(pass, checkUnnecessaryBlankQ2, node); ok {
+			report.Report(pass, node, "unnecessary assignment to the blank identifier",
+				report.FilterGenerated(),
+				report.Fixes(edit.Fix("simplify channel receive operation", edit.ReplaceWithNode(pass.Fset, node, m.State["recv"].(ast.Node)))))
+		}
+	}
+
+	fn3 := func(node ast.Node) {
+		rs := node.(*ast.RangeStmt)
+
+		// for _
+		if rs.Value == nil && astutil.IsBlank(rs.Key) {
+			report.Report(pass, rs.Key, "unnecessary assignment to the blank identifier",
+				report.FilterGenerated(),
+				report.Fixes(edit.Fix("remove assignment to blank identifier", edit.Delete(edit.Range{rs.Key.Pos(), rs.TokPos + 1}))))
+		}
+
+		// for _, _
+		if astutil.IsBlank(rs.Key) && astutil.IsBlank(rs.Value) {
+			// FIXME we should mark both key and value
+			report.Report(pass, rs.Key, "unnecessary assignment to the blank identifier",
+				report.FilterGenerated(),
+				report.Fixes(edit.Fix("remove assignment to blank identifier", edit.Delete(edit.Range{rs.Key.Pos(), rs.TokPos + 1}))))
+		}
+
+		// for x, _
+		if !astutil.IsBlank(rs.Key) && astutil.IsBlank(rs.Value) {
+			report.Report(pass, rs.Value, "unnecessary assignment to the blank identifier",
+				report.FilterGenerated(),
+				report.Fixes(edit.Fix("remove assignment to blank identifier", edit.Delete(edit.Range{rs.Key.End(), rs.Value.End()}))))
+		}
+	}
+
+	code.Preorder(pass, fn1, (*ast.AssignStmt)(nil))
+	if code.IsGoVersion(pass, 4) {
+		code.Preorder(pass, fn3, (*ast.RangeStmt)(nil))
+	}
+	return nil, nil
+}
+
+func CheckSimplerStructConversion(pass *analysis.Pass) (interface{}, error) {
+	fn := func(node ast.Node, stack []ast.Node) {
+		if unary, ok := stack[len(stack)-2].(*ast.UnaryExpr); ok && unary.Op == token.AND {
+			// Do not suggest type conversion between pointers
+			return
+		}
+
+		lit := node.(*ast.CompositeLit)
+		typ1, _ := pass.TypesInfo.TypeOf(lit.Type).(*types.Named)
+		if typ1 == nil {
+			return
+		}
+		s1, ok := typ1.Underlying().(*types.Struct)
+		if !ok {
+			return
+		}
+
+		var typ2 *types.Named
+		var ident *ast.Ident
+		getSelType := func(expr ast.Expr) (types.Type, *ast.Ident, bool) {
+			sel, ok := expr.(*ast.SelectorExpr)
+			if !ok {
+				return nil, nil, false
+			}
+			ident, ok := sel.X.(*ast.Ident)
+			if !ok {
+				return nil, nil, false
+			}
+			typ := pass.TypesInfo.TypeOf(sel.X)
+			return typ, ident, typ != nil
+		}
+		if len(lit.Elts) == 0 {
+			return
+		}
+		if s1.NumFields() != len(lit.Elts) {
+			return
+		}
+		for i, elt := range lit.Elts {
+			var t types.Type
+			var id *ast.Ident
+			var ok bool
+			switch elt := elt.(type) {
+			case *ast.SelectorExpr:
+				t, id, ok = getSelType(elt)
+				if !ok {
+					return
+				}
+				if i >= s1.NumFields() || s1.Field(i).Name() != elt.Sel.Name {
+					return
+				}
+			case *ast.KeyValueExpr:
+				var sel *ast.SelectorExpr
+				sel, ok = elt.Value.(*ast.SelectorExpr)
+				if !ok {
+					return
+				}
+
+				if elt.Key.(*ast.Ident).Name != sel.Sel.Name {
+					return
+				}
+				t, id, ok = getSelType(elt.Value)
+			}
+			if !ok {
+				return
+			}
+			// All fields must be initialized from the same object
+			if ident != nil && ident.Obj != id.Obj {
+				return
+			}
+			typ2, _ = t.(*types.Named)
+			if typ2 == nil {
+				return
+			}
+			ident = id
+		}
+
+		if typ2 == nil {
+			return
+		}
+
+		if typ1.Obj().Pkg() != typ2.Obj().Pkg() {
+			// Do not suggest type conversions between different
+			// packages. Types in different packages might only match
+			// by coincidence. Furthermore, if the dependency ever
+			// adds more fields to its type, it could break the code
+			// that relies on the type conversion to work.
+			return
+		}
+
+		s2, ok := typ2.Underlying().(*types.Struct)
+		if !ok {
+			return
+		}
+		if typ1 == typ2 {
+			return
+		}
+		if code.IsGoVersion(pass, 8) {
+			if !types.IdenticalIgnoreTags(s1, s2) {
+				return
+			}
+		} else {
+			if !types.Identical(s1, s2) {
+				return
+			}
+		}
+
+		r := &ast.CallExpr{
+			Fun:  lit.Type,
+			Args: []ast.Expr{ident},
+		}
+		report.Report(pass, node,
+			fmt.Sprintf("should convert %s (type %s) to %s instead of using struct literal", ident.Name, typ2.Obj().Name(), typ1.Obj().Name()),
+			report.FilterGenerated(),
+			report.Fixes(edit.Fix("use type conversion", edit.ReplaceWithNode(pass.Fset, node, r))))
+	}
+	code.PreorderStack(pass, fn, (*ast.CompositeLit)(nil))
+	return nil, nil
+}
+
+func CheckTrim(pass *analysis.Pass) (interface{}, error) {
+	sameNonDynamic := func(node1, node2 ast.Node) bool {
+		if reflect.TypeOf(node1) != reflect.TypeOf(node2) {
+			return false
+		}
+
+		switch node1 := node1.(type) {
+		case *ast.Ident:
+			return node1.Obj == node2.(*ast.Ident).Obj
+		case *ast.SelectorExpr:
+			return report.Render(pass, node1) == report.Render(pass, node2)
+		case *ast.IndexExpr:
+			return report.Render(pass, node1) == report.Render(pass, node2)
+		}
+		return false
+	}
+
+	isLenOnIdent := func(fn ast.Expr, ident ast.Expr) bool {
+		call, ok := fn.(*ast.CallExpr)
+		if !ok {
+			return false
+		}
+		if fn, ok := call.Fun.(*ast.Ident); !ok || fn.Name != "len" {
+			return false
+		}
+		if len(call.Args) != 1 {
+			return false
+		}
+		return sameNonDynamic(call.Args[knowledge.Arg("len.v")], ident)
+	}
+
+	fn := func(node ast.Node) {
+		var pkg string
+		var fun string
+
+		ifstmt := node.(*ast.IfStmt)
+		if ifstmt.Init != nil {
+			return
+		}
+		if ifstmt.Else != nil {
+			return
+		}
+		if len(ifstmt.Body.List) != 1 {
+			return
+		}
+		condCall, ok := ifstmt.Cond.(*ast.CallExpr)
+		if !ok {
+			return
+		}
+
+		condCallName := code.CallName(pass, condCall)
+		switch condCallName {
+		case "strings.HasPrefix":
+			pkg = "strings"
+			fun = "HasPrefix"
+		case "strings.HasSuffix":
+			pkg = "strings"
+			fun = "HasSuffix"
+		case "strings.Contains":
+			pkg = "strings"
+			fun = "Contains"
+		case "bytes.HasPrefix":
+			pkg = "bytes"
+			fun = "HasPrefix"
+		case "bytes.HasSuffix":
+			pkg = "bytes"
+			fun = "HasSuffix"
+		case "bytes.Contains":
+			pkg = "bytes"
+			fun = "Contains"
+		default:
+			return
+		}
+
+		assign, ok := ifstmt.Body.List[0].(*ast.AssignStmt)
+		if !ok {
+			return
+		}
+		if assign.Tok != token.ASSIGN {
+			return
+		}
+		if len(assign.Lhs) != 1 || len(assign.Rhs) != 1 {
+			return
+		}
+		if !sameNonDynamic(condCall.Args[0], assign.Lhs[0]) {
+			return
+		}
+
+		switch rhs := assign.Rhs[0].(type) {
+		case *ast.CallExpr:
+			if len(rhs.Args) < 2 || !sameNonDynamic(condCall.Args[0], rhs.Args[0]) || !sameNonDynamic(condCall.Args[1], rhs.Args[1]) {
+				return
+			}
+
+			rhsName := code.CallName(pass, rhs)
+			if condCallName == "strings.HasPrefix" && rhsName == "strings.TrimPrefix" ||
+				condCallName == "strings.HasSuffix" && rhsName == "strings.TrimSuffix" ||
+				condCallName == "strings.Contains" && rhsName == "strings.Replace" ||
+				condCallName == "bytes.HasPrefix" && rhsName == "bytes.TrimPrefix" ||
+				condCallName == "bytes.HasSuffix" && rhsName == "bytes.TrimSuffix" ||
+				condCallName == "bytes.Contains" && rhsName == "bytes.Replace" {
+				report.Report(pass, ifstmt, fmt.Sprintf("should replace this if statement with an unconditional %s", rhsName), report.FilterGenerated())
+			}
+			return
+		case *ast.SliceExpr:
+			slice := rhs
+			if !ok {
+				return
+			}
+			if slice.Slice3 {
+				return
+			}
+			if !sameNonDynamic(slice.X, condCall.Args[0]) {
+				return
+			}
+			var index ast.Expr
+			switch fun {
+			case "HasPrefix":
+				// TODO(dh) We could detect a High that is len(s), but another
+				// rule will already flag that, anyway.
+				if slice.High != nil {
+					return
+				}
+				index = slice.Low
+			case "HasSuffix":
+				if slice.Low != nil {
+					n, ok := code.ExprToInt(pass, slice.Low)
+					if !ok || n != 0 {
+						return
+					}
+				}
+				index = slice.High
+			}
+
+			switch index := index.(type) {
+			case *ast.CallExpr:
+				if fun != "HasPrefix" {
+					return
+				}
+				if fn, ok := index.Fun.(*ast.Ident); !ok || fn.Name != "len" {
+					return
+				}
+				if len(index.Args) != 1 {
+					return
+				}
+				id3 := index.Args[knowledge.Arg("len.v")]
+				switch oid3 := condCall.Args[1].(type) {
+				case *ast.BasicLit:
+					if pkg != "strings" {
+						return
+					}
+					lit, ok := id3.(*ast.BasicLit)
+					if !ok {
+						return
+					}
+					s1, ok1 := code.ExprToString(pass, lit)
+					s2, ok2 := code.ExprToString(pass, condCall.Args[1])
+					if !ok1 || !ok2 || s1 != s2 {
+						return
+					}
+				default:
+					if !sameNonDynamic(id3, oid3) {
+						return
+					}
+				}
+			case *ast.BasicLit, *ast.Ident:
+				if fun != "HasPrefix" {
+					return
+				}
+				if pkg != "strings" {
+					return
+				}
+				string, ok1 := code.ExprToString(pass, condCall.Args[1])
+				int, ok2 := code.ExprToInt(pass, slice.Low)
+				if !ok1 || !ok2 || int != int64(len(string)) {
+					return
+				}
+			case *ast.BinaryExpr:
+				if fun != "HasSuffix" {
+					return
+				}
+				if index.Op != token.SUB {
+					return
+				}
+				if !isLenOnIdent(index.X, condCall.Args[0]) ||
+					!isLenOnIdent(index.Y, condCall.Args[1]) {
+					return
+				}
+			default:
+				return
+			}
+
+			var replacement string
+			switch fun {
+			case "HasPrefix":
+				replacement = "TrimPrefix"
+			case "HasSuffix":
+				replacement = "TrimSuffix"
+			}
+			report.Report(pass, ifstmt, fmt.Sprintf("should replace this if statement with an unconditional %s.%s", pkg, replacement),
+				report.ShortRange(),
+				report.FilterGenerated())
+		}
+	}
+	code.Preorder(pass, fn, (*ast.IfStmt)(nil))
+	return nil, nil
+}
+
+var (
+	checkLoopSlideQ = pattern.MustParse(`
+		(ForStmt
+			(AssignStmt initvar@(Ident _) _ (BasicLit "INT" "0"))
+			(BinaryExpr initvar "<" limit@(Ident _))
+			(IncDecStmt initvar "++")
+			[(AssignStmt
+				(IndexExpr slice@(Ident _) initvar)
+				"="
+				(IndexExpr slice (BinaryExpr offset@(Ident _) "+" initvar)))])`)
+	checkLoopSlideR = pattern.MustParse(`
+		(CallExpr
+			(Ident "copy")
+			[(SliceExpr slice nil limit nil)
+				(SliceExpr slice offset nil nil)])`)
+)
+
+func CheckLoopSlide(pass *analysis.Pass) (interface{}, error) {
+	// TODO(dh): detect bs[i+offset] in addition to bs[offset+i]
+	// TODO(dh): consider merging this function with LintLoopCopy
+	// TODO(dh): detect length that is an expression, not a variable name
+	// TODO(dh): support sliding to a different offset than the beginning of the slice
+
+	fn := func(node ast.Node) {
+		loop := node.(*ast.ForStmt)
+		m, edits, ok := code.MatchAndEdit(pass, checkLoopSlideQ, checkLoopSlideR, loop)
+		if !ok {
+			return
+		}
+		if _, ok := pass.TypesInfo.TypeOf(m.State["slice"].(*ast.Ident)).Underlying().(*types.Slice); !ok {
+			return
+		}
+
+		report.Report(pass, loop, "should use copy() instead of loop for sliding slice elements",
+			report.ShortRange(),
+			report.FilterGenerated(),
+			report.Fixes(edit.Fix("use copy() instead of loop", edits...)))
+	}
+	code.Preorder(pass, fn, (*ast.ForStmt)(nil))
+	return nil, nil
+}
+
+var (
+	checkMakeLenCapQ1 = pattern.MustParse(`(CallExpr (Builtin "make") [typ size@(BasicLit "INT" "0")])`)
+	checkMakeLenCapQ2 = pattern.MustParse(`(CallExpr (Builtin "make") [typ size size])`)
+)
+
+func CheckMakeLenCap(pass *analysis.Pass) (interface{}, error) {
+	fn := func(node ast.Node) {
+		if pass.Pkg.Path() == "runtime_test" && filepath.Base(pass.Fset.Position(node.Pos()).Filename) == "map_test.go" {
+			// special case of runtime tests testing map creation
+			return
+		}
+		if m, ok := code.Match(pass, checkMakeLenCapQ1, node); ok {
+			T := m.State["typ"].(ast.Expr)
+			size := m.State["size"].(ast.Node)
+			if _, ok := pass.TypesInfo.TypeOf(T).Underlying().(*types.Slice); ok {
+				return
+			}
+			report.Report(pass, size, fmt.Sprintf("should use make(%s) instead", report.Render(pass, T)), report.FilterGenerated())
+		} else if m, ok := code.Match(pass, checkMakeLenCapQ2, node); ok {
+			// TODO(dh): don't consider sizes identical if they're
+			// dynamic. for example: make(T, <-ch, <-ch).
+			T := m.State["typ"].(ast.Expr)
+			size := m.State["size"].(ast.Node)
+			report.Report(pass, size,
+				fmt.Sprintf("should use make(%s, %s) instead", report.Render(pass, T), report.Render(pass, size)),
+				report.FilterGenerated())
+		}
+	}
+	code.Preorder(pass, fn, (*ast.CallExpr)(nil))
+	return nil, nil
+}
+
+var (
+	checkAssertNotNilFn1Q = pattern.MustParse(`
+		(IfStmt
+			(AssignStmt [(Ident "_") ok@(Object _)] _ [(TypeAssertExpr assert@(Object _) _)])
+			(Or
+				(BinaryExpr ok "&&" (BinaryExpr assert "!=" (Builtin "nil")))
+				(BinaryExpr (BinaryExpr assert "!=" (Builtin "nil")) "&&" ok))
+			_
+			_)`)
+	checkAssertNotNilFn2Q = pattern.MustParse(`
+		(IfStmt
+			nil
+			(BinaryExpr lhs@(Object _) "!=" (Builtin "nil"))
+			[
+				ifstmt@(IfStmt
+					(AssignStmt [(Ident "_") ok@(Object _)] _ [(TypeAssertExpr lhs _)])
+					ok
+					_
+					_)
+			]
+			nil)`)
+)
+
+func CheckAssertNotNil(pass *analysis.Pass) (interface{}, error) {
+	fn1 := func(node ast.Node) {
+		m, ok := code.Match(pass, checkAssertNotNilFn1Q, node)
+		if !ok {
+			return
+		}
+		assert := m.State["assert"].(types.Object)
+		assign := m.State["ok"].(types.Object)
+		report.Report(pass, node, fmt.Sprintf("when %s is true, %s can't be nil", assign.Name(), assert.Name()),
+			report.ShortRange(),
+			report.FilterGenerated())
+	}
+	fn2 := func(node ast.Node) {
+		m, ok := code.Match(pass, checkAssertNotNilFn2Q, node)
+		if !ok {
+			return
+		}
+		ifstmt := m.State["ifstmt"].(*ast.IfStmt)
+		lhs := m.State["lhs"].(types.Object)
+		assignIdent := m.State["ok"].(types.Object)
+		report.Report(pass, ifstmt, fmt.Sprintf("when %s is true, %s can't be nil", assignIdent.Name(), lhs.Name()),
+			report.ShortRange(),
+			report.FilterGenerated())
+	}
+	// OPT(dh): merge fn1 and fn2
+	code.Preorder(pass, fn1, (*ast.IfStmt)(nil))
+	code.Preorder(pass, fn2, (*ast.IfStmt)(nil))
+	return nil, nil
+}
+
+func CheckDeclareAssign(pass *analysis.Pass) (interface{}, error) {
+	hasMultipleAssignments := func(root ast.Node, ident *ast.Ident) bool {
+		num := 0
+		ast.Inspect(root, func(node ast.Node) bool {
+			if num >= 2 {
+				return false
+			}
+			assign, ok := node.(*ast.AssignStmt)
+			if !ok {
+				return true
+			}
+			for _, lhs := range assign.Lhs {
+				if oident, ok := lhs.(*ast.Ident); ok {
+					if oident.Obj == ident.Obj {
+						num++
+					}
+				}
+			}
+
+			return true
+		})
+		return num >= 2
+	}
+	fn := func(node ast.Node) {
+		block := node.(*ast.BlockStmt)
+		if len(block.List) < 2 {
+			return
+		}
+		for i, stmt := range block.List[:len(block.List)-1] {
+			_ = i
+			decl, ok := stmt.(*ast.DeclStmt)
+			if !ok {
+				continue
+			}
+			gdecl, ok := decl.Decl.(*ast.GenDecl)
+			if !ok || gdecl.Tok != token.VAR || len(gdecl.Specs) != 1 {
+				continue
+			}
+			vspec, ok := gdecl.Specs[0].(*ast.ValueSpec)
+			if !ok || len(vspec.Names) != 1 || len(vspec.Values) != 0 {
+				continue
+			}
+
+			assign, ok := block.List[i+1].(*ast.AssignStmt)
+			if !ok || assign.Tok != token.ASSIGN {
+				continue
+			}
+			if len(assign.Lhs) != 1 || len(assign.Rhs) != 1 {
+				continue
+			}
+			ident, ok := assign.Lhs[0].(*ast.Ident)
+			if !ok {
+				continue
+			}
+			if vspec.Names[0].Obj != ident.Obj {
+				continue
+			}
+
+			if refersTo(pass, assign.Rhs[0], pass.TypesInfo.ObjectOf(ident)) {
+				continue
+			}
+			if hasMultipleAssignments(block, ident) {
+				continue
+			}
+
+			r := &ast.GenDecl{
+				Specs: []ast.Spec{
+					&ast.ValueSpec{
+						Names:  vspec.Names,
+						Values: []ast.Expr{assign.Rhs[0]},
+						Type:   vspec.Type,
+					},
+				},
+				Tok: gdecl.Tok,
+			}
+			report.Report(pass, decl, "should merge variable declaration with assignment on next line",
+				report.FilterGenerated(),
+				report.Fixes(edit.Fix("merge declaration with assignment", edit.ReplaceWithNode(pass.Fset, edit.Range{decl.Pos(), assign.End()}, r))))
+		}
+	}
+	code.Preorder(pass, fn, (*ast.BlockStmt)(nil))
+	return nil, nil
+}
+
+func CheckRedundantBreak(pass *analysis.Pass) (interface{}, error) {
+	fn1 := func(node ast.Node) {
+		clause := node.(*ast.CaseClause)
+		if len(clause.Body) < 2 {
+			return
+		}
+		branch, ok := clause.Body[len(clause.Body)-1].(*ast.BranchStmt)
+		if !ok || branch.Tok != token.BREAK || branch.Label != nil {
+			return
+		}
+		report.Report(pass, branch, "redundant break statement", report.FilterGenerated())
+	}
+	fn2 := func(node ast.Node) {
+		var ret *ast.FieldList
+		var body *ast.BlockStmt
+		switch x := node.(type) {
+		case *ast.FuncDecl:
+			ret = x.Type.Results
+			body = x.Body
+		case *ast.FuncLit:
+			ret = x.Type.Results
+			body = x.Body
+		default:
+			lint.ExhaustiveTypeSwitch(node)
+		}
+		// if the func has results, a return can't be redundant.
+		// similarly, if there are no statements, there can be
+		// no return.
+		if ret != nil || body == nil || len(body.List) < 1 {
+			return
+		}
+		rst, ok := body.List[len(body.List)-1].(*ast.ReturnStmt)
+		if !ok {
+			return
+		}
+		// we don't need to check rst.Results as we already
+		// checked x.Type.Results to be nil.
+		report.Report(pass, rst, "redundant return statement", report.FilterGenerated())
+	}
+	code.Preorder(pass, fn1, (*ast.CaseClause)(nil))
+	code.Preorder(pass, fn2, (*ast.FuncDecl)(nil), (*ast.FuncLit)(nil))
+	return nil, nil
+}
+
+func isStringer(T types.Type, msCache *gotypeutil.MethodSetCache) bool {
+	ms := msCache.MethodSet(T)
+	sel := ms.Lookup(nil, "String")
+	if sel == nil {
+		return false
+	}
+	fn, ok := sel.Obj().(*types.Func)
+	if !ok {
+		// should be unreachable
+		return false
+	}
+	sig := fn.Type().(*types.Signature)
+	if sig.Params().Len() != 0 {
+		return false
+	}
+	if sig.Results().Len() != 1 {
+		return false
+	}
+	if !typeutil.IsType(sig.Results().At(0).Type(), "string") {
+		return false
+	}
+	return true
+}
+
+func isFormatter(T types.Type, msCache *gotypeutil.MethodSetCache) bool {
+	// TODO(dh): this function also exists in staticcheck/lint.go – deduplicate.
+
+	ms := msCache.MethodSet(T)
+	sel := ms.Lookup(nil, "Format")
+	if sel == nil {
+		return false
+	}
+	fn, ok := sel.Obj().(*types.Func)
+	if !ok {
+		// should be unreachable
+		return false
+	}
+	sig := fn.Type().(*types.Signature)
+	if sig.Params().Len() != 2 {
+		return false
+	}
+	// TODO(dh): check the types of the arguments for more
+	// precision
+	if sig.Results().Len() != 0 {
+		return false
+	}
+	return true
+}
+
+var checkRedundantSprintfQ = pattern.MustParse(`(CallExpr (Function "fmt.Sprintf") [format arg])`)
+
+func CheckRedundantSprintf(pass *analysis.Pass) (interface{}, error) {
+	fn := func(node ast.Node) {
+		m, ok := code.Match(pass, checkRedundantSprintfQ, node)
+		if !ok {
+			return
+		}
+
+		format := m.State["format"].(ast.Expr)
+		arg := m.State["arg"].(ast.Expr)
+		if s, ok := code.ExprToString(pass, format); !ok || s != "%s" {
+			return
+		}
+		typ := pass.TypesInfo.TypeOf(arg)
+		irpkg := pass.ResultOf[buildir.Analyzer].(*buildir.IR).Pkg
+
+		if types.TypeString(typ, nil) == "reflect.Value" {
+			// printing with %s produces output different from using
+			// the String method
+			return
+		}
+
+		if isFormatter(typ, &irpkg.Prog.MethodSets) {
+			// the type may choose to handle %s in arbitrary ways
+			return
+		}
+
+		if isStringer(typ, &irpkg.Prog.MethodSets) {
+			replacement := &ast.CallExpr{
+				Fun: &ast.SelectorExpr{
+					X:   arg,
+					Sel: &ast.Ident{Name: "String"},
+				},
+			}
+			report.Report(pass, node, "should use String() instead of fmt.Sprintf",
+				report.Fixes(edit.Fix("replace with call to String method", edit.ReplaceWithNode(pass.Fset, node, replacement))))
+			return
+		}
+
+		if typ.Underlying() == types.Universe.Lookup("string").Type() {
+			if typ == types.Universe.Lookup("string").Type() {
+				report.Report(pass, node, "the argument is already a string, there's no need to use fmt.Sprintf",
+					report.FilterGenerated(),
+					report.Fixes(edit.Fix("remove unnecessary call to fmt.Sprintf", edit.ReplaceWithNode(pass.Fset, node, arg))))
+			} else {
+				replacement := &ast.CallExpr{
+					Fun:  &ast.Ident{Name: "string"},
+					Args: []ast.Expr{arg},
+				}
+				report.Report(pass, node, "the argument's underlying type is a string, should use a simple conversion instead of fmt.Sprintf",
+					report.FilterGenerated(),
+					report.Fixes(edit.Fix("replace with conversion to string", edit.ReplaceWithNode(pass.Fset, node, replacement))))
+			}
+		}
+	}
+	code.Preorder(pass, fn, (*ast.CallExpr)(nil))
+	return nil, nil
+}
+
+var (
+	checkErrorsNewSprintfQ = pattern.MustParse(`(CallExpr (Function "errors.New") [(CallExpr (Function "fmt.Sprintf") args)])`)
+	checkErrorsNewSprintfR = pattern.MustParse(`(CallExpr (SelectorExpr (Ident "fmt") (Ident "Errorf")) args)`)
+)
+
+func CheckErrorsNewSprintf(pass *analysis.Pass) (interface{}, error) {
+	fn := func(node ast.Node) {
+		if _, edits, ok := code.MatchAndEdit(pass, checkErrorsNewSprintfQ, checkErrorsNewSprintfR, node); ok {
+			// TODO(dh): the suggested fix may leave an unused import behind
+			report.Report(pass, node, "should use fmt.Errorf(...) instead of errors.New(fmt.Sprintf(...))",
+				report.FilterGenerated(),
+				report.Fixes(edit.Fix("use fmt.Errorf", edits...)))
+		}
+	}
+	code.Preorder(pass, fn, (*ast.CallExpr)(nil))
+	return nil, nil
+}
+
+func CheckRangeStringRunes(pass *analysis.Pass) (interface{}, error) {
+	return sharedcheck.CheckRangeStringRunes(pass)
+}
+
+var checkNilCheckAroundRangeQ = pattern.MustParse(`
+	(IfStmt
+		nil
+		(BinaryExpr x@(Object _) "!=" (Builtin "nil"))
+		[(RangeStmt _ _ _ x _)]
+		nil)`)
+
+func CheckNilCheckAroundRange(pass *analysis.Pass) (interface{}, error) {
+	fn := func(node ast.Node) {
+		m, ok := code.Match(pass, checkNilCheckAroundRangeQ, node)
+		if !ok {
+			return
+		}
+		switch m.State["x"].(types.Object).Type().Underlying().(type) {
+		case *types.Slice, *types.Map:
+			report.Report(pass, node, "unnecessary nil check around range",
+				report.ShortRange(),
+				report.FilterGenerated())
+
+		}
+	}
+	code.Preorder(pass, fn, (*ast.IfStmt)(nil))
+	return nil, nil
+}
+
+func isPermissibleSort(pass *analysis.Pass, node ast.Node) bool {
+	call := node.(*ast.CallExpr)
+	typeconv, ok := call.Args[0].(*ast.CallExpr)
+	if !ok {
+		return true
+	}
+
+	sel, ok := typeconv.Fun.(*ast.SelectorExpr)
+	if !ok {
+		return true
+	}
+	name := code.SelectorName(pass, sel)
+	switch name {
+	case "sort.IntSlice", "sort.Float64Slice", "sort.StringSlice":
+	default:
+		return true
+	}
+
+	return false
+}
+
+func CheckSortHelpers(pass *analysis.Pass) (interface{}, error) {
+	type Error struct {
+		node ast.Node
+		msg  string
+	}
+	var allErrors []Error
+	fn := func(node ast.Node) {
+		var body *ast.BlockStmt
+		switch node := node.(type) {
+		case *ast.FuncLit:
+			body = node.Body
+		case *ast.FuncDecl:
+			body = node.Body
+		default:
+			lint.ExhaustiveTypeSwitch(node)
+		}
+		if body == nil {
+			return
+		}
+
+		var errors []Error
+		permissible := false
+		fnSorts := func(node ast.Node) bool {
+			if permissible {
+				return false
+			}
+			if !code.IsCallTo(pass, node, "sort.Sort") {
+				return true
+			}
+			if isPermissibleSort(pass, node) {
+				permissible = true
+				return false
+			}
+			call := node.(*ast.CallExpr)
+			typeconv := call.Args[knowledge.Arg("sort.Sort.data")].(*ast.CallExpr)
+			sel := typeconv.Fun.(*ast.SelectorExpr)
+			name := code.SelectorName(pass, sel)
+
+			switch name {
+			case "sort.IntSlice":
+				errors = append(errors, Error{node, "should use sort.Ints(...) instead of sort.Sort(sort.IntSlice(...))"})
+			case "sort.Float64Slice":
+				errors = append(errors, Error{node, "should use sort.Float64s(...) instead of sort.Sort(sort.Float64Slice(...))"})
+			case "sort.StringSlice":
+				errors = append(errors, Error{node, "should use sort.Strings(...) instead of sort.Sort(sort.StringSlice(...))"})
+			}
+			return true
+		}
+		ast.Inspect(body, fnSorts)
+
+		if permissible {
+			return
+		}
+		allErrors = append(allErrors, errors...)
+	}
+	code.Preorder(pass, fn, (*ast.FuncLit)(nil), (*ast.FuncDecl)(nil))
+	sort.Slice(allErrors, func(i, j int) bool {
+		return allErrors[i].node.Pos() < allErrors[j].node.Pos()
+	})
+	var prev token.Pos
+	for _, err := range allErrors {
+		if err.node.Pos() == prev {
+			continue
+		}
+		prev = err.node.Pos()
+		report.Report(pass, err.node, err.msg, report.FilterGenerated())
+	}
+	return nil, nil
+}
+
+var checkGuardedDeleteQ = pattern.MustParse(`
+	(IfStmt
+		(AssignStmt
+			[(Ident "_") ok@(Ident _)]
+			":="
+			(IndexExpr m key))
+		ok
+		[call@(CallExpr (Builtin "delete") [m key])]
+		nil)`)
+
+func CheckGuardedDelete(pass *analysis.Pass) (interface{}, error) {
+	fn := func(node ast.Node) {
+		if m, ok := code.Match(pass, checkGuardedDeleteQ, node); ok {
+			report.Report(pass, node, "unnecessary guard around call to delete",
+				report.ShortRange(),
+				report.FilterGenerated(),
+				report.Fixes(edit.Fix("remove guard", edit.ReplaceWithNode(pass.Fset, node, m.State["call"].(ast.Node)))))
+		}
+	}
+
+	code.Preorder(pass, fn, (*ast.IfStmt)(nil))
+	return nil, nil
+}
+
+var (
+	checkSimplifyTypeSwitchQ = pattern.MustParse(`
+		(TypeSwitchStmt
+			nil
+			expr@(TypeAssertExpr ident@(Ident _) _)
+			body)`)
+	checkSimplifyTypeSwitchR = pattern.MustParse(`(AssignStmt ident ":=" expr)`)
+)
+
+func CheckSimplifyTypeSwitch(pass *analysis.Pass) (interface{}, error) {
+	fn := func(node ast.Node) {
+		m, ok := code.Match(pass, checkSimplifyTypeSwitchQ, node)
+		if !ok {
+			return
+		}
+		stmt := node.(*ast.TypeSwitchStmt)
+		expr := m.State["expr"].(ast.Node)
+		ident := m.State["ident"].(*ast.Ident)
+
+		x := pass.TypesInfo.ObjectOf(ident)
+		var allOffenders []*ast.TypeAssertExpr
+		canSuggestFix := true
+		for _, clause := range stmt.Body.List {
+			clause := clause.(*ast.CaseClause)
+			if len(clause.List) != 1 {
+				continue
+			}
+			hasUnrelatedAssertion := false
+			var offenders []*ast.TypeAssertExpr
+			ast.Inspect(clause, func(node ast.Node) bool {
+				assert2, ok := node.(*ast.TypeAssertExpr)
+				if !ok {
+					return true
+				}
+				ident, ok := assert2.X.(*ast.Ident)
+				if !ok {
+					hasUnrelatedAssertion = true
+					return false
+				}
+				if pass.TypesInfo.ObjectOf(ident) != x {
+					hasUnrelatedAssertion = true
+					return false
+				}
+
+				if !types.Identical(pass.TypesInfo.TypeOf(clause.List[0]), pass.TypesInfo.TypeOf(assert2.Type)) {
+					hasUnrelatedAssertion = true
+					return false
+				}
+				offenders = append(offenders, assert2)
+				return true
+			})
+			if !hasUnrelatedAssertion {
+				// don't flag cases that have other type assertions
+				// unrelated to the one in the case clause. often
+				// times, this is done for symmetry, when two
+				// different values have to be asserted to the same
+				// type.
+				allOffenders = append(allOffenders, offenders...)
+			}
+			canSuggestFix = canSuggestFix && !hasUnrelatedAssertion
+		}
+		if len(allOffenders) != 0 {
+			var opts []report.Option
+			for _, offender := range allOffenders {
+				opts = append(opts, report.Related(offender, "could eliminate this type assertion"))
+			}
+			opts = append(opts, report.FilterGenerated())
+
+			msg := fmt.Sprintf("assigning the result of this type assertion to a variable (switch %s := %s.(type)) could eliminate type assertions in switch cases",
+				report.Render(pass, ident), report.Render(pass, ident))
+			if canSuggestFix {
+				var edits []analysis.TextEdit
+				edits = append(edits, edit.ReplaceWithPattern(pass, checkSimplifyTypeSwitchR, m.State, expr))
+				for _, offender := range allOffenders {
+					edits = append(edits, edit.ReplaceWithNode(pass.Fset, offender, offender.X))
+				}
+				opts = append(opts, report.Fixes(edit.Fix("simplify type switch", edits...)))
+				report.Report(pass, expr, msg, opts...)
+			} else {
+				report.Report(pass, expr, msg, opts...)
+			}
+		}
+	}
+	code.Preorder(pass, fn, (*ast.TypeSwitchStmt)(nil))
+	return nil, nil
+}
+
+func CheckRedundantCanonicalHeaderKey(pass *analysis.Pass) (interface{}, error) {
+	fn := func(node ast.Node) {
+		call := node.(*ast.CallExpr)
+		callName := code.CallName(pass, call)
+		switch callName {
+		case "(net/http.Header).Add", "(net/http.Header).Del", "(net/http.Header).Get", "(net/http.Header).Set":
+		default:
+			return
+		}
+
+		if !code.IsCallTo(pass, call.Args[0], "net/http.CanonicalHeaderKey") {
+			return
+		}
+
+		report.Report(pass, call,
+			fmt.Sprintf("calling net/http.CanonicalHeaderKey on the 'key' argument of %s is redundant", callName),
+			report.FilterGenerated(),
+			report.Fixes(edit.Fix("remove call to CanonicalHeaderKey", edit.ReplaceWithNode(pass.Fset, call.Args[0], call.Args[0].(*ast.CallExpr).Args[0]))))
+	}
+	code.Preorder(pass, fn, (*ast.CallExpr)(nil))
+	return nil, nil
+}
+
+var checkUnnecessaryGuardQ = pattern.MustParse(`
+	(Or
+		(IfStmt
+			(AssignStmt [(Ident "_") ok@(Ident _)] ":=" indexexpr@(IndexExpr _ _))
+			ok
+			set@(AssignStmt indexexpr "=" (CallExpr (Builtin "append") indexexpr:values))
+			(AssignStmt indexexpr "=" (CompositeLit _ values)))
+		(IfStmt
+			(AssignStmt [(Ident "_") ok] ":=" indexexpr@(IndexExpr _ _))
+			ok
+			set@(AssignStmt indexexpr "+=" value)
+			(AssignStmt indexexpr "=" value))
+		(IfStmt
+			(AssignStmt [(Ident "_") ok] ":=" indexexpr@(IndexExpr _ _))
+			ok
+			set@(IncDecStmt indexexpr "++")
+			(AssignStmt indexexpr "=" (BasicLit "INT" "1"))))`)
+
+func CheckUnnecessaryGuard(pass *analysis.Pass) (interface{}, error) {
+	fn := func(node ast.Node) {
+		if m, ok := code.Match(pass, checkUnnecessaryGuardQ, node); ok {
+			if code.MayHaveSideEffects(pass, m.State["indexexpr"].(ast.Expr), nil) {
+				return
+			}
+			report.Report(pass, node, "unnecessary guard around map access",
+				report.ShortRange(),
+				report.Fixes(edit.Fix("simplify map access", edit.ReplaceWithNode(pass.Fset, node, m.State["set"].(ast.Node)))))
+		}
+	}
+	code.Preorder(pass, fn, (*ast.IfStmt)(nil))
+	return nil, nil
+}
+
+var (
+	checkElaborateSleepQ = pattern.MustParse(`(SelectStmt (CommClause (UnaryExpr "<-" (CallExpr (Function "time.After") [arg])) body))`)
+	checkElaborateSleepR = pattern.MustParse(`(CallExpr (SelectorExpr (Ident "time") (Ident "Sleep")) [arg])`)
+)
+
+func CheckElaborateSleep(pass *analysis.Pass) (interface{}, error) {
+	fn := func(node ast.Node) {
+		if m, ok := code.Match(pass, checkElaborateSleepQ, node); ok {
+			if body, ok := m.State["body"].([]ast.Stmt); ok && len(body) == 0 {
+				report.Report(pass, node, "should use time.Sleep instead of elaborate way of sleeping",
+					report.ShortRange(),
+					report.FilterGenerated(),
+					report.Fixes(edit.Fix("Use time.Sleep", edit.ReplaceWithPattern(pass, checkElaborateSleepR, m.State, node))))
+			} else {
+				// TODO(dh): we could make a suggested fix if the body
+				// doesn't declare or shadow any identifiers
+				report.Report(pass, node, "should use time.Sleep instead of elaborate way of sleeping",
+					report.ShortRange(),
+					report.FilterGenerated())
+			}
+		}
+	}
+	code.Preorder(pass, fn, (*ast.SelectStmt)(nil))
+	return nil, nil
+}
+
+var checkPrintSprintQ = pattern.MustParse(`
+	(Or
+		(CallExpr
+			fn@(Or
+				(Function "fmt.Print")
+				(Function "fmt.Sprint")
+				(Function "fmt.Println")
+				(Function "fmt.Sprintln"))
+			[(CallExpr (Function "fmt.Sprintf") f:_)])
+		(CallExpr
+			fn@(Or
+				(Function "fmt.Fprint")
+				(Function "fmt.Fprintln"))
+			[_ (CallExpr (Function "fmt.Sprintf") f:_)]))`)
+
+func CheckPrintSprintf(pass *analysis.Pass) (interface{}, error) {
+	fn := func(node ast.Node) {
+		m, ok := code.Match(pass, checkPrintSprintQ, node)
+		if !ok {
+			return
+		}
+
+		name := m.State["fn"].(*types.Func).Name()
+		var msg string
+		switch name {
+		case "Print", "Fprint", "Sprint":
+			newname := name + "f"
+			msg = fmt.Sprintf("should use fmt.%s instead of fmt.%s(fmt.Sprintf(...))", newname, name)
+		case "Println", "Fprintln", "Sprintln":
+			if _, ok := m.State["f"].(*ast.BasicLit); !ok {
+				// This may be an instance of
+				// fmt.Println(fmt.Sprintf(arg, ...)) where arg is an
+				// externally provided format string and the caller
+				// cannot guarantee that the format string ends with a
+				// newline.
+				return
+			}
+			newname := name[:len(name)-2] + "f"
+			msg = fmt.Sprintf("should use fmt.%s instead of fmt.%s(fmt.Sprintf(...)) (but don't forget the newline)", newname, name)
+		}
+		report.Report(pass, node, msg,
+			report.FilterGenerated())
+	}
+	code.Preorder(pass, fn, (*ast.CallExpr)(nil))
+	return nil, nil
+}
+
+var checkSprintLiteralQ = pattern.MustParse(`
+	(CallExpr
+		fn@(Or
+			(Function "fmt.Sprint")
+			(Function "fmt.Sprintf"))
+		[lit@(BasicLit "STRING" _)])`)
+
+func CheckSprintLiteral(pass *analysis.Pass) (interface{}, error) {
+	// We only flag calls with string literals, not expressions of
+	// type string, because some people use fmt.Sprint(s) as a pattern
+	// for copying strings, which may be useful when extracing a small
+	// substring from a large string.
+	fn := func(node ast.Node) {
+		m, ok := code.Match(pass, checkSprintLiteralQ, node)
+		if !ok {
+			return
+		}
+		callee := m.State["fn"].(*types.Func)
+		lit := m.State["lit"].(*ast.BasicLit)
+		if callee.Name() == "Sprintf" {
+			if strings.ContainsRune(lit.Value, '%') {
+				// This might be a format string
+				return
+			}
+		}
+		report.Report(pass, node, fmt.Sprintf("unnecessary use of fmt.%s", callee.Name()),
+			report.FilterGenerated(),
+			report.Fixes(edit.Fix("Replace with string literal", edit.ReplaceWithNode(pass.Fset, node, lit))))
+	}
+	code.Preorder(pass, fn, (*ast.CallExpr)(nil))
+	return nil, nil
+}