Add staticcheck tool

vendor/honnef.co/go/tools/simple/s1021/s1021.go

@@ -0,0 +1,118 @@
+package s1021
+
+import (
+	"go/ast"
+	"go/token"
+
+	"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"
+
+	"golang.org/x/tools/go/analysis"
+	"golang.org/x/tools/go/analysis/passes/inspect"
+)
+
+var SCAnalyzer = lint.InitializeAnalyzer(&lint.Analyzer{
+	Analyzer: &analysis.Analyzer{
+		Name:     "S1021",
+		Run:      run,
+		Requires: []*analysis.Analyzer{inspect.Analyzer, generated.Analyzer},
+	},
+	Doc: &lint.RawDocumentation{
+		Title: `Merge variable declaration and assignment`,
+		Before: `
+var x uint
+x = 1`,
+		After:   `var x uint = 1`,
+		Since:   "2017.1",
+		MergeIf: lint.MergeIfAny,
+	},
+})
+
+var Analyzer = SCAnalyzer.Analyzer
+
+func run(pass *analysis.Pass) (any, 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 pass.TypesInfo.ObjectOf(oident) == pass.TypesInfo.ObjectOf(ident) {
+						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 pass.TypesInfo.ObjectOf(vspec.Names[0]) != pass.TypesInfo.ObjectOf(ident) {
+				continue
+			}
+
+			if code.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
+}