Add staticcheck tool

vendor/honnef.co/go/tools/simple/s1018/s1018.go

@@ -0,0 +1,78 @@
+package s1018
+
+import (
+	"go/ast"
+
+	"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/go/types/typeutil"
+	"honnef.co/go/tools/pattern"
+
+	"golang.org/x/tools/go/analysis"
+)
+
+var SCAnalyzer = lint.InitializeAnalyzer(&lint.Analyzer{
+	Analyzer: &analysis.Analyzer{
+		Name:     "S1018",
+		Run:      run,
+		Requires: append([]*analysis.Analyzer{generated.Analyzer}, code.RequiredAnalyzers...),
+	},
+	Doc: &lint.RawDocumentation{
+		Title: `Use \"copy\" for sliding elements`,
+		Text: `\'copy()\' permits using the same source and destination slice, even with
+overlapping ranges. This makes it ideal for sliding elements in a
+slice.`,
+
+		Before: `
+for i := 0; i < n; i++ {
+    bs[i] = bs[offset+i]
+}`,
+		After:   `copy(bs[:n], bs[offset:])`,
+		Since:   "2017.1",
+		MergeIf: lint.MergeIfAny,
+	},
+})
+
+var Analyzer = SCAnalyzer.Analyzer
+
+var (
+	checkLoopSlideQ = pattern.MustParse(`
+		(ForStmt
+			(AssignStmt initvar@(Ident _) _ (IntegerLiteral "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 run(pass *analysis.Pass) (any, 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
+
+	for node, m := range code.Matches(pass, checkLoopSlideQ) {
+		typ := pass.TypesInfo.TypeOf(m.State["slice"].(*ast.Ident))
+		// The pattern probably needs a core type, but All is fine, too. Either way we only accept slices.
+		if !typeutil.All(typ, typeutil.IsSlice) {
+			continue
+		}
+
+		edits := code.EditMatch(pass, node, m, checkLoopSlideR)
+		report.Report(pass, node, "should use copy() instead of loop for sliding slice elements",
+			report.ShortRange(),
+			report.FilterGenerated(),
+			report.Fixes(edit.Fix("Use copy() instead of loop", edits...)))
+	}
+	return nil, nil
+}