checkers: ignore labeled continue in select statement (#1158)

Fixes #1130

checkers/internal/lintutil/astfind.go

@@ -7,21 +7,35 @@ import (
 )
 
 // FindNode applies pred for root and all it's childs until it returns true.
+// If followFunc is defined, it's called before following any node to check whether it needs to be followed.
+// followFunc has to return true in order to continuing traversing the node and return false otherwise.
 // Matched node is returned.
 // If none of the nodes matched predicate, nil is returned.
-func FindNode(root ast.Node, pred func(ast.Node) bool) ast.Node {
-	var found ast.Node
-	astutil.Apply(root, nil, func(cur *astutil.Cursor) bool {
-		if pred(cur.Node()) {
-			found = cur.Node()
-			return false
+func FindNode(root ast.Node, followFunc, pred func(ast.Node) bool) ast.Node {
+	var (
+		found   ast.Node
+		preFunc func(*astutil.Cursor) bool
+	)
+
+	if followFunc != nil {
+		preFunc = func(cur *astutil.Cursor) bool {
+			return followFunc(cur.Node())
 		}
-		return true
-	})
+	}
+
+	astutil.Apply(root,
+		preFunc,
+		func(cur *astutil.Cursor) bool {
+			if pred(cur.Node()) {
+				found = cur.Node()
+				return false
+			}
+			return true
+		})
 	return found
 }
 
 // ContainsNode reports whether `FindNode(root, pred)!=nil`.
 func ContainsNode(root ast.Node, pred func(ast.Node) bool) bool {
-	return FindNode(root, pred) != nil
+	return FindNode(root, nil, pred) != nil
 }

checkers/testdata/unlabelStmt/negative_tests.go

@@ -147,3 +147,16 @@ outer2:
 		_ = x
 	}
 }
+
+func twoLoopsWithSelect(c chan int) {
+outer2:
+	for {
+		println("foo")
+		for {
+			select {
+			case <-c:
+				continue outer2
+			}
+		}
+	}
+}

checkers/typeSwitchVar_checker.go

@@ -74,7 +74,7 @@ func (c *typeSwitchVarChecker) checkTypeSwitch(root *ast.TypeSwitchStmt) {
 		// Create artificial node just for matching.
 		assert1 := ast.TypeAssertExpr{X: expr, Type: clause.List[0]}
 		for _, stmt := range clause.Body {
-			assert2 := lintutil.FindNode(stmt, func(x ast.Node) bool {
+			assert2 := lintutil.FindNode(stmt, nil, func(x ast.Node) bool {
 				return astequal.Node(&assert1, x)
 			})
 			if object == c.ctx.TypesInfo.ObjectOf(identOf(assert2)) {

checkers/unlabelStmt_checker.go

@@ -87,6 +87,7 @@ func (c *unlabelStmtChecker) VisitStmt(stmt ast.Stmt) {
 	// Only for loops: if last stmt in list is a loop
 	// that contains labeled "continue" to the outer loop label,
 	// it can be refactored to use "break" instead.
+	// Exceptions: select statements with a labeled "continue" are ignored.
 	if c.isLoop(labeled.Stmt) {
 		body := c.blockStmtOf(labeled.Stmt)
 		if len(body.List) == 0 {
@@ -96,11 +97,21 @@ func (c *unlabelStmtChecker) VisitStmt(stmt ast.Stmt) {
 		if !c.isLoop(last) {
 			return
 		}
-		br := lintutil.FindNode(c.blockStmtOf(last), func(n ast.Node) bool {
-			br, ok := n.(*ast.BranchStmt)
-			return ok && br.Label != nil &&
-				br.Label.Name == name && br.Tok == token.CONTINUE
-		})
+		br := lintutil.FindNode(c.blockStmtOf(last),
+			func(n ast.Node) bool {
+				switch n.(type) {
+				case *ast.SelectStmt:
+					return false
+				default:
+					return true
+				}
+			},
+			func(n ast.Node) bool {
+				br, ok := n.(*ast.BranchStmt)
+				return ok && br.Label != nil &&
+					br.Label.Name == name && br.Tok == token.CONTINUE
+			})
+
 		if br != nil {
 			c.warnLabeledContinue(br, name)
 		}