Add rules

defaultrule/ranges.go

@@ -0,0 +1,60 @@
+package defaultrule
+
+import (
+	"fmt"
+	"go/ast"
+
+	"github.com/mgechev/revive/file"
+	"github.com/mgechev/revive/rule"
+)
+
+// LintRangesRule lints given else constructs.
+type LintRangesRule struct{}
+
+// Apply applies the rule to given file.
+func (r *LintRangesRule) Apply(file *file.File, arguments rule.Arguments) []rule.Failure {
+	var failures []rule.Failure
+
+	onFailure := func(failure rule.Failure) {
+		failures = append(failures, failure)
+	}
+
+	astFile := file.GetAST()
+	w := &lintRanges{astFile, onFailure}
+	ast.Walk(w, astFile)
+	return failures
+}
+
+// Name returns the rule name.
+func (r *LintRangesRule) Name() string {
+	return "no-else-return"
+}
+
+type lintRanges struct {
+	file      *ast.File
+	onFailure func(rule.Failure)
+}
+
+func (w *lintRanges) Visit(node ast.Node) ast.Visitor {
+	rs, ok := node.(*ast.RangeStmt)
+	if !ok {
+		return w
+	}
+	if rs.Value == nil {
+		// for x = range m { ... }
+		return w // single var form
+	}
+	if !isIdent(rs.Value, "_") {
+		// for ?, y = range m { ... }
+		return w
+	}
+
+	w.onFailure(rule.Failure{
+		Failure:    fmt.Sprintf("should omit 2nd value from range; this loop is equivalent to `for %s %s range ...`", render(rs.Key), rs.Tok),
+		Confidence: 1,
+		Node:       rs.Value,
+	})
+
+	// TODO: replacement?
+	return w
+}

defaultrule/utils.go

@@ -128,3 +128,8 @@ func validType(T types.Type) bool {
 		T != types.Typ[types.Invalid] &&
 		!strings.Contains(T.String(), "invalid type") // good but not foolproof
 }
+
+func isPkgDot(expr ast.Expr, pkg, name string) bool {
+	sel, ok := expr.(*ast.SelectorExpr)
+	return ok && isIdent(sel.X, pkg) && isIdent(sel.Sel, name)
+}