cmd/vet: handle added string constants in printf format check

Fixes #4599.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/7226067

diff --git a/src/cmd/vet/print.go b/src/cmd/vet/print.go
index a402d3de41788924ccdca4ae3ebe6f206b8fcdaa..ea85edac1dead17126c5ddb607c01851f1bee122 100644 (file)
--- a/src/cmd/vet/print.go
+++ b/src/cmd/vet/print.go
@@ -11,6 +11,7 @@ import (
        "fmt"
        "go/ast"
        "go/token"
+       "strconv"
        "strings"
        "unicode/utf8"
 )
@@ -62,6 +63,23 @@ func (f *File) literal(value ast.Expr) *ast.BasicLit {
        switch v := value.(type) {
        case *ast.BasicLit:
                return v
+       case *ast.ParenExpr:
+               return f.literal(v.X)
+       case *ast.BinaryExpr:
+               if v.Op != token.ADD {
+                       break
+               }
+               litX := f.literal(v.X)
+               litY := f.literal(v.Y)
+               if litX != nil && litY != nil {
+                       lit := *litX
+                       x, errX := strconv.Unquote(litX.Value)
+                       y, errY := strconv.Unquote(litY.Value)
+                       if errX == nil && errY == nil {
+                               lit.Value = strconv.Quote(x + y)
+                               return &lit
+                       }
+               }
        case *ast.Ident:
                // See if it's a constant or initial value (we can't tell the difference).
                if v.Obj == nil || v.Obj.Decl == nil {
@@ -101,7 +119,10 @@ func (f *File) checkPrintf(call *ast.CallExpr, name string, skip int) {
        if lit.Kind != token.STRING {
                f.Badf(call.Pos(), "literal %v not a string in call to", lit.Value, name)
        }
-       format := lit.Value
+       format, err := strconv.Unquote(lit.Value)
+       if err != nil {
+               f.Badf(call.Pos(), "invalid quoted string literal")
+       }
        if !strings.Contains(format, "%") {
                if len(call.Args) > skip+1 {
                        f.Badf(call.Pos(), "no formatting directive in %s call", name)
@@ -282,6 +303,7 @@ func BadFunctionUsedInTests() {
        fmt.Println()                      // not an error
        fmt.Println("%s", "hi")            // ERROR "possible formatting directive in Println call"
        fmt.Printf("%s", "hi", 3)          // ERROR "wrong number of args in Printf call"
+       fmt.Printf("%"+("s"), "hi", 3)     // ERROR "wrong number of args in Printf call"
        fmt.Printf("%s%%%d", "hi", 3)      // correct
        fmt.Printf("%08s", "woo")          // correct
        fmt.Printf("% 8s", "woo")          // correct