SA5001: clarify message

Clarify the message by putting the function name in there.

Closes: dominikhgh-1489
Closes: dominikhgh-1554 [via git-merge-pr]

staticcheck/sa5001/sa5001.go

@@ -91,7 +91,8 @@ func run(pass *analysis.Pass) (interface{}, error) {
 			if sel.Sel.Name != "Close" {
 				continue
 			}
-			report.Report(pass, def, fmt.Sprintf("should check returned error before deferring %s", report.Render(pass, def.Call)))
+			report.Report(pass, def, fmt.Sprintf("should check error returned from %s() before deferring %s",
+				report.Render(pass, call.Fun), report.Render(pass, def.Call)))
 		}
 	}
 	code.Preorder(pass, fn, (*ast.BlockStmt)(nil))

staticcheck/sa5001/testdata/go1.0/CheckEarlyDefer/CheckEarlyDefer.go

@@ -1,6 +1,9 @@
 package pkg
 
-import "io"
+import (
+	"io"
+	"os"
+)
 
 func fn1() (io.ReadCloser, error) {
 	return nil, nil
@@ -10,13 +13,19 @@ type T struct {
 	rc io.ReadCloser
 }
 
+type T2 struct{}
+
+func (T2) create() (io.ReadCloser, error) {
+	return nil, nil
+}
+
 func fn3() (T, error) {
 	return T{}, nil
 }
 
 func fn2() {
 	rc, err := fn1()
-	defer rc.Close() //@ diag(`should check returned error before deferring rc.Close`)
+	defer rc.Close() //@ diag(`should check error returned from fn1() before deferring rc.Close`)
 	if err != nil {
 		println()
 	}
@@ -31,7 +40,20 @@ func fn2() {
 	defer rc.Close()
 
 	t, err := fn3()
-	defer t.rc.Close() //@ diag(`should check returned error before deferring t.rc.Close`)
+	defer t.rc.Close() //@ diag(`should check error returned from fn3() before deferring t.rc.Close`)
+	if err != nil {
+		println()
+	}
+
+	fp, err := os.Open("path")
+	defer fp.Close() //@ diag(`should check error returned from os.Open() before deferring fp.Close()`)
+	if err != nil {
+		println()
+	}
+
+	var t2 T2
+	rc2, err := t2.create()
+	defer rc2.Close() //@ diag(`should check error returned from t2.create() before deferring rc2.Close()`)
 	if err != nil {
 		println()
 	}