pkg/proc: do not check decl line for FunctionArguments (#3254)

Fixes a bug where we cannot get locals (including arguments and return
values) from a given scope because the line number state machine ends up
in an invalid state because of this parameter being set to false.

_fixtures/traceprog.go

@@ -0,0 +1,13 @@
+package main
+
+import "fmt"
+
+func callme(i int) int {
+	return i * i
+}
+
+func main() {
+	j := 0
+	j += callme(2)
+	fmt.Println(j)
+}

cmd/dlv/dlv_test.go

@@ -1036,6 +1036,31 @@ func TestTrace(t *testing.T) {
 	cmd.Wait()
 }
 
+func TestTrace2(t *testing.T) {
+	dlvbin, tmpdir := getDlvBin(t)
+	defer os.RemoveAll(tmpdir)
+
+	expected := []byte("> goroutine(1): main.callme(2)\n>> goroutine(1): => (4)\n")
+
+	fixtures := protest.FindFixturesDir()
+	cmd := exec.Command(dlvbin, "trace", "--output", filepath.Join(tmpdir, "__debug"), filepath.Join(fixtures, "traceprog.go"), "callme")
+	rdr, err := cmd.StderrPipe()
+	assertNoError(err, t, "stderr pipe")
+	defer rdr.Close()
+
+	cmd.Dir = filepath.Join(fixtures, "buildtest")
+
+	assertNoError(cmd.Start(), t, "running trace")
+
+	output, err := ioutil.ReadAll(rdr)
+	assertNoError(err, t, "ReadAll")
+
+	if !bytes.Contains(output, expected) {
+		t.Fatalf("expected:\n%s\ngot:\n%s", string(expected), string(output))
+	}
+	cmd.Wait()
+}
+
 func TestTraceMultipleGoroutines(t *testing.T) {
 	dlvbin, tmpdir := getDlvBin(t)
 	defer os.RemoveAll(tmpdir)

pkg/proc/eval.go

@@ -474,7 +474,7 @@ func (scope *EvalScope) LocalVariables(cfg LoadConfig) ([]*Variable, error) {
 
 // FunctionArguments returns the name, value, and type of all current function arguments.
 func (scope *EvalScope) FunctionArguments(cfg LoadConfig) ([]*Variable, error) {
-	vars, err := scope.Locals(0)
+	vars, err := scope.Locals(localsNoDeclLineCheck)
 	if err != nil {
 		return nil, err
 	}