don't replace all consts with vars

In some cases, such as iotas or when constants are later required to be constants,
we could break compilation. Be more conservative.

Fixes #32.

strings.go

@@ -18,11 +18,28 @@ func obfuscateLiterals(files []*ast.File) []*ast.File {
 			return true
 		}
 
-		// constants are not possibly if we want to obfuscate literals, therfore
-		// remove all constants and replace them by variables
-		if t.Tok == token.CONST {
-			t.Tok = token.VAR
+		if t.Tok != token.CONST {
+			return true
 		}
+
+		for _, spec := range t.Specs {
+			spec, ok := spec.(*ast.ValueSpec)
+			if !ok {
+				// cannot happen because ast.GenDecl with token.Const are always of type ast.ValueSpec
+				return false
+			}
+
+			for _, val := range spec.Values {
+				if v, ok := val.(*ast.BasicLit); !ok || v.Kind != token.STRING {
+					return false // skip the block if it contains non basic literals
+				}
+			}
+		}
+
+		// constants are not possible if we want to obfuscate literals, therefore
+		// move all constant blocks which only contain strings to variables
+		t.Tok = token.VAR
+
 		return true
 	}
 

testdata/scripts/strings.txt

@@ -4,6 +4,8 @@ exec ./main
 cmp stdout main.stdout
 ! binsubstr main$exe 'Lorem' 'ipsum' 'dolor' 'first assign' 'second assign' 'First Line' 'Second Line' 'map value' 'to obfuscate' 'also obfuscate'
 
+binsubstr main$exe 'Skip this block,' 'also skip this'
+
 [short] stop # checking that the build is reproducible is slow
 
 # Also check that the binary is reproducible.
@@ -28,6 +30,24 @@ const (
 Second Line`
 )
 
+const (
+	skip1 = "Skip this block,"
+	i     = 1
+)
+
+const (
+	foo = iota
+	bar
+
+	skip2 = "also skip this"
+)
+
+const arrayLen = 4
+
+var array [arrayLen]byte
+
+type typeAlias [arrayLen]byte
+
 var variable = "ipsum"
 
 func main() {
@@ -57,6 +77,10 @@ func main() {
 	fmt.Println(testMap["map key"])
 
 	fmt.Println("another literal")
+
+	fmt.Println(skip1, skip2)
+
+	fmt.Println(i, foo, bar)
 }
 
 -- main.stdout --
@@ -70,4 +94,6 @@ second assign
 to obfuscate
 also obfuscate
 map value
-another literal
+another literal
+Skip this block, also skip this
+1 0 1