Flag uses of deprecated objects

Might interest the folks at golang/lint#238

staticcheck/README.md

@@ -60,6 +60,7 @@ The following things are currently checked by staticcheck:
 | SA1016     | Trapping a signal that cannot be trapped                                                                                                              |
 | SA1017     | Channels used with signal.Notify should be buffered                                                                                                   |
 | SA1018     | `strings.Replace` called with n == 0, which does nothing                                                                                              |
+| SA1019     | Using a deprecated function, variable, constant or field                                                                                              |
 |            |                                                                                                                                                       |
 | **SA2???** | **Concurrency issues**                                                                                                                                |
 | SA2000     | `sync.WaitGroup.Add` called inside the goroutine, leading to a race condition                                                                         |

staticcheck/lint.go

@@ -13,6 +13,7 @@ import (
 	"regexp"
 	"strconv"
 	"strings"
+	"sync"
 	texttemplate "text/template"
 	"time"
 	"unicode/utf8"
@@ -88,6 +89,9 @@ func (d FunctionDescriptions) Merge(fn *ssa.Function, desc Function) {
 
 type Checker struct {
 	funcDescs FunctionDescriptions
+
+	depmu          sync.Mutex
+	deprecatedObjs map[types.Object]string
 }
 
 func NewChecker() *Checker {
@@ -115,6 +119,7 @@ func (c *Checker) Funcs() map[string]lint.Func {
 		"SA1016": c.CheckUntrappableSignal,
 		"SA1017": c.CheckUnbufferedSignalChan,
 		"SA1018": c.CheckStringsReplaceZero,
+		"SA1019": c.CheckDeprecated,
 
 		"SA2000": c.CheckWaitgroupAdd,
 		"SA2001": c.CheckEmptyCriticalSection,
@@ -182,6 +187,7 @@ func terminates(fn *ssa.Function) (ret bool) {
 
 func (c *Checker) Init(prog *lint.Program) {
 	c.funcDescs = FunctionDescriptions{}
+	c.deprecatedObjs = map[types.Object]string{}
 
 	for fn, desc := range stdlibDescs {
 		c.funcDescs[fn] = desc
@@ -2646,3 +2652,78 @@ func (c *Checker) CheckPureFunctions(f *lint.File) {
 	}
 	f.Walk(fn)
 }
+
+func (c *Checker) CheckDeprecated(f *lint.File) {
+	c.depmu.Lock()
+	defer c.depmu.Unlock()
+
+	fn := func(node ast.Node) bool {
+		sel, ok := node.(*ast.SelectorExpr)
+		if !ok {
+			return true
+		}
+		obj := f.Pkg.TypesInfo.ObjectOf(sel.Sel)
+		if obj.Pkg() == nil {
+			return true
+		}
+		if f.Pkg.PkgInfo.Pkg == obj.Pkg() || obj.Pkg().Path()+"_test" == f.Pkg.PkgInfo.Pkg.Path() {
+			// Don't flag stuff in our own package
+			return true
+		}
+		if alt, ok := c.deprecatedObjs[obj]; ok {
+			if alt == "" {
+				return true
+			}
+			f.Errorf(sel, "%s is deprecated: %s", f.Render(sel), alt)
+			return true
+		}
+		_, path, _ := f.Program.PathEnclosingInterval(obj.Pos(), obj.Pos())
+		if len(path) <= 2 {
+			c.deprecatedObjs[obj] = ""
+			return true
+		}
+		var docs []*ast.CommentGroup
+		switch n := path[1].(type) {
+		case *ast.FuncDecl:
+			docs = append(docs, n.Doc)
+		case *ast.Field:
+			docs = append(docs, n.Doc)
+		case *ast.ValueSpec:
+			docs = append(docs, n.Doc)
+			if len(path) >= 3 {
+				if n, ok := path[2].(*ast.GenDecl); ok {
+					docs = append(docs, n.Doc)
+				}
+			}
+		case *ast.TypeSpec:
+			docs = append(docs, n.Doc)
+			if len(path) >= 3 {
+				if n, ok := path[2].(*ast.GenDecl); ok {
+					docs = append(docs, n.Doc)
+				}
+			}
+		default:
+			c.deprecatedObjs[obj] = ""
+			return true
+		}
+
+		for _, doc := range docs {
+			if doc == nil {
+				continue
+			}
+			parts := strings.Split(doc.Text(), "\n\n")
+			last := parts[len(parts)-1]
+			if !strings.HasPrefix(last, "Deprecated: ") {
+				continue
+			}
+			alt := last[len("Deprecated: "):]
+			alt = strings.Replace(alt, "\n", " ", -1)
+			f.Errorf(sel, "%s is deprecated: %s", f.Render(sel), alt)
+			c.deprecatedObjs[obj] = alt
+			return true
+		}
+		c.deprecatedObjs[obj] = ""
+		return true
+	}
+	f.Walk(fn)
+}

staticcheck/testdata/CheckDeprecated.go

@@ -0,0 +1,18 @@
+package pkg
+
+import (
+	"compress/flate"
+	"net/http"
+	"os"
+	"syscall"
+)
+
+func fn(err error) {
+	var r *http.Request
+	_ = r.Cancel                        // MATCH /Use the Context and WithContext methods/
+	_ = syscall.StringByteSlice("")     // MATCH /Use ByteSliceFromString instead/
+	_ = os.SEEK_SET                     // MATCH /Use io.SeekStart, io.SeekCurrent, and io.SeekEnd/
+	if err == http.ErrWriteAfterFlush { // MATCH /ErrWriteAfterFlush is no longer used/
+	}
+	var _ flate.ReadError // MATCH /No longer returned/
+}