Add staticcheck tool

vendor/honnef.co/go/tools/simple/s1011/s1011.go

@@ -0,0 +1,137 @@
+package s1011
+
+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/facts/purity"
+	"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:     "S1011",
+		Run:      run,
+		Requires: append([]*analysis.Analyzer{generated.Analyzer, purity.Analyzer}, code.RequiredAnalyzers...),
+	},
+	Doc: &lint.RawDocumentation{
+		Title: `Use a single \'append\' to concatenate two slices`,
+		Before: `
+for _, e := range y {
+    x = append(x, e)
+}
+
+for i := range y {
+    x = append(x, y[i])
+}
+
+for i := range y {
+    v := y[i]
+    x = append(x, v)
+}`,
+
+		After: `
+x = append(x, y...)
+x = append(x, y...)
+x = append(x, y...)`,
+		Since: "2017.1",
+		// MergeIfAll because y might not be a slice under all build tags.
+		MergeIf: lint.MergeIfAll,
+	},
+})
+
+var Analyzer = SCAnalyzer.Analyzer
+
+var checkLoopAppendQ = pattern.MustParse(`
+(Or
+	(RangeStmt
+		(Ident "_")
+		val@(Object _)
+		_
+		x
+		[(AssignStmt [lhs] "=" [(CallExpr (Builtin "append") [lhs val])])])
+	(RangeStmt
+		idx@(Object _)
+		nil
+		_
+		x
+		[(AssignStmt [lhs] "=" [(CallExpr (Builtin "append") [lhs (IndexExpr x idx)])])])
+	(RangeStmt
+		idx@(Object _)
+		nil
+		_
+		x
+		[(AssignStmt val@(Object _) ":=" (IndexExpr x idx))
+		(AssignStmt [lhs] "=" [(CallExpr (Builtin "append") [lhs val])])]))`)
+
+func run(pass *analysis.Pass) (any, error) {
+	pure := pass.ResultOf[purity.Analyzer].(purity.Result)
+
+	for node, m := range code.Matches(pass, checkLoopAppendQ) {
+		if val, ok := m.State["val"].(types.Object); ok && code.RefersTo(pass, m.State["lhs"].(ast.Expr), val) {
+			continue
+		}
+
+		if m.State["idx"] != nil && code.MayHaveSideEffects(pass, m.State["x"].(ast.Expr), pure) {
+			// When using an index-based loop, x gets evaluated repeatedly and thus should be pure.
+			// This doesn't matter for value-based loops, because x only gets evaluated once.
+			continue
+		}
+
+		if idx, ok := m.State["idx"].(types.Object); ok && code.RefersTo(pass, m.State["lhs"].(ast.Expr), idx) {
+			// The lhs mustn't refer to the index loop variable.
+			continue
+		}
+
+		if code.MayHaveSideEffects(pass, m.State["lhs"].(ast.Expr), pure) {
+			// The lhs may be dynamic and return different values on each iteration. For example:
+			//
+			// 	func bar() map[int][]int { /* return one of several maps */ }
+			//
+			// 	func foo(x []int, y [][]int) {
+			// 		for i := range x {
+			// 			bar()[0] = append(bar()[0], x[i])
+			// 		}
+			// 	}
+			//
+			// The dynamic nature of the lhs might also affect the value of the index.
+			continue
+		}
+
+		src := pass.TypesInfo.TypeOf(m.State["x"].(ast.Expr))
+		dst := pass.TypesInfo.TypeOf(m.State["lhs"].(ast.Expr))
+		if !types.Identical(src, dst) {
+			continue
+		}
+
+		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))))
+	}
+	return nil, nil
+}