Support function params, ignore backquotes

Author: jgautheron

go.mod

@@ -0,0 +1,3 @@
+module github.com/jgautheron/goconst
+
+go 1.13

tests/foo_test.go

@@ -0,0 +1,9 @@
+package main
+
+import "fmt"
+
+func foo() {
+	foo := "test"
+	boo := "test"
+	fmt.Println(foo, boo)
+}

tests/main.go

@@ -0,0 +1,30 @@
+package main
+
+import (
+	"fmt"
+	"strings"
+)
+
+const Foo = "bar"
+
+var url string
+
+func main() {
+	if strings.HasPrefix(url, "http://") {
+		url = strings.TrimPrefix(url, "http://")
+	}
+	url = strings.TrimPrefix(url, "/")
+	fmt.Println(url)
+}
+
+func testCase() string {
+	test := `test`
+	if url == "test" {
+		return test
+	}
+	switch url {
+	case "moo":
+		return ""
+	}
+	return "foo"
+}

visitor.go

@@ -95,14 +95,24 @@ func (v *treeVisitor) Visit(node ast.Node) ast.Visitor {
 				v.addString(lit.Value, lit.Pos())
 			}
 		}
+
+	// fn("http://")
+	case *ast.CallExpr:
+		for _, item := range t.Args {
+			lit, ok := item.(*ast.BasicLit)
+			if ok && v.isSupported(lit.Kind) {
+				v.addString(lit.Value, lit.Pos())
+			}
+		}
 	}
 
 	return v
 }
 
 // addString adds a string in the map along with its position in the tree.
 func (v *treeVisitor) addString(str string, pos token.Pos) {
-	str = strings.Replace(str, `"`, "", 2)
+	// Drop first and last character, quote, backquote...
+	str = str[1 : len(str)-1]
 
 	// Ignore empty strings
 	if len(str) == 0 {