Add staticcheck tool

vendor/honnef.co/go/tools/simple/s1001/s1001.go

@@ -0,0 +1,190 @@
+package s1001
+
+import (
+	"fmt"
+	"go/ast"
+	"go/token"
+	"go/types"
+
+	"honnef.co/go/tools/analysis/code"
+	"honnef.co/go/tools/analysis/edit"
+	"honnef.co/go/tools/analysis/facts/generated"
+	"honnef.co/go/tools/analysis/lint"
+	"honnef.co/go/tools/analysis/report"
+	"honnef.co/go/tools/pattern"
+
+	"golang.org/x/tools/go/analysis"
+)
+
+var SCAnalyzer = lint.InitializeAnalyzer(&lint.Analyzer{
+	Analyzer: &analysis.Analyzer{
+		Name:     "S1001",
+		Run:      run,
+		Requires: append([]*analysis.Analyzer{generated.Analyzer}, code.RequiredAnalyzers...),
+	},
+	Doc: &lint.RawDocumentation{
+		Title: `Replace for loop with call to copy`,
+		Text: `
+Use \'copy()\' for copying elements from one slice to another. For
+arrays of identical size, you can use simple assignment.`,
+		Before: `
+for i, x := range src {
+    dst[i] = x
+}`,
+		After: `copy(dst, src)`,
+		Since: "2017.1",
+		// MergeIfAll because the types of src and dst might be different under different build tags.
+		// You shouldn't write code like that…
+		MergeIf: lint.MergeIfAll,
+	},
+})
+
+var Analyzer = SCAnalyzer.Analyzer
+
+var (
+	checkLoopCopyQ = pattern.MustParse(`
+		(Or
+			(RangeStmt
+				key@(Ident _) value@(Ident _) ":=" src
+				[(AssignStmt (IndexExpr dst key) "=" value)])
+			(RangeStmt
+				key@(Ident _) nil ":=" src
+				[(AssignStmt (IndexExpr dst key) "=" (IndexExpr src key))])
+			(ForStmt
+				(AssignStmt key@(Ident _) ":=" (IntegerLiteral "0"))
+				(BinaryExpr key "<" (CallExpr (Symbol "len") [src]))
+				(IncDecStmt key "++")
+				[(AssignStmt (IndexExpr dst key) "=" (IndexExpr src key))]))`)
+)
+
+func run(pass *analysis.Pass) (any, error) {
+	// TODO revisit once range doesn't require a structural type
+
+	isInvariant := func(k, v types.Object, node ast.Expr) bool {
+		if code.MayHaveSideEffects(pass, node, nil) {
+			return false
+		}
+		invariant := true
+		ast.Inspect(node, func(node ast.Node) bool {
+			if node, ok := node.(*ast.Ident); ok {
+				obj := pass.TypesInfo.ObjectOf(node)
+				if obj == k || obj == v {
+					// don't allow loop bodies like 'a[i][i] = v'
+					invariant = false
+					return false
+				}
+			}
+			return true
+		})
+		return invariant
+	}
+
+	var elType func(T types.Type) (el types.Type, isArray bool, isArrayPointer bool, ok bool)
+	elType = func(T types.Type) (el types.Type, isArray bool, isArrayPointer bool, ok bool) {
+		switch typ := T.Underlying().(type) {
+		case *types.Slice:
+			return typ.Elem(), false, false, true
+		case *types.Array:
+			return typ.Elem(), true, false, true
+		case *types.Pointer:
+			el, isArray, _, ok = elType(typ.Elem())
+			return el, isArray, true, ok
+		default:
+			return nil, false, false, false
+		}
+	}
+
+	for node, m := range code.Matches(pass, checkLoopCopyQ) {
+		src := m.State["src"].(ast.Expr)
+		dst := m.State["dst"].(ast.Expr)
+
+		k := pass.TypesInfo.ObjectOf(m.State["key"].(*ast.Ident))
+		var v types.Object
+		if value, ok := m.State["value"]; ok {
+			v = pass.TypesInfo.ObjectOf(value.(*ast.Ident))
+		}
+		if !isInvariant(k, v, dst) {
+			continue
+		}
+		if !isInvariant(k, v, src) {
+			// For example: 'for i := range foo()'
+			continue
+		}
+
+		Tsrc := pass.TypesInfo.TypeOf(src)
+		Tdst := pass.TypesInfo.TypeOf(dst)
+		TsrcElem, TsrcArray, TsrcPointer, ok := elType(Tsrc)
+		if !ok {
+			continue
+		}
+		if TsrcPointer {
+			Tsrc = Tsrc.Underlying().(*types.Pointer).Elem()
+		}
+		TdstElem, TdstArray, TdstPointer, ok := elType(Tdst)
+		if !ok {
+			continue
+		}
+		if TdstPointer {
+			Tdst = Tdst.Underlying().(*types.Pointer).Elem()
+		}
+
+		if !types.Identical(TsrcElem, TdstElem) {
+			continue
+		}
+
+		if TsrcArray && TdstArray && types.Identical(Tsrc, Tdst) {
+			if TsrcPointer {
+				src = &ast.StarExpr{
+					X: src,
+				}
+			}
+			if TdstPointer {
+				dst = &ast.StarExpr{
+					X: dst,
+				}
+			}
+			r := &ast.AssignStmt{
+				Lhs: []ast.Expr{dst},
+				Rhs: []ast.Expr{src},
+				Tok: token.ASSIGN,
+			}
+
+			report.Report(pass, node, "should copy arrays using assignment instead of using a loop",
+				report.FilterGenerated(),
+				report.ShortRange(),
+				report.Fixes(edit.Fix("Replace loop with assignment", edit.ReplaceWithNode(pass.Fset, node, r))))
+		} else {
+			tv, err := types.Eval(pass.Fset, pass.Pkg, node.Pos(), "copy")
+			if err == nil && tv.IsBuiltin() {
+				to := "to"
+				from := "from"
+				src := m.State["src"].(ast.Expr)
+				if TsrcArray {
+					from = "from[:]"
+					src = &ast.SliceExpr{
+						X: src,
+					}
+				}
+				dst := m.State["dst"].(ast.Expr)
+				if TdstArray {
+					to = "to[:]"
+					dst = &ast.SliceExpr{
+						X: dst,
+					}
+				}
+
+				r := &ast.CallExpr{
+					Fun:  &ast.Ident{Name: "copy"},
+					Args: []ast.Expr{dst, src},
+				}
+				opts := []report.Option{
+					report.ShortRange(),
+					report.FilterGenerated(),
+					report.Fixes(edit.Fix("Replace loop with call to copy()", edit.ReplaceWithNode(pass.Fset, node, r))),
+				}
+				report.Report(pass, node, fmt.Sprintf("should use copy(%s, %s) instead of a loop", to, from), opts...)
+			}
+		}
+	}
+	return nil, nil
+}