From 8d562cef9934917ba43f342a6a3553f704bd9f8e Mon Sep 17 00:00:00 2001
From: Evgeniy Stratonikov <evgeniy@nspcc.ru>
Date: Thu, 30 Sep 2021 10:18:31 +0300
Subject: [PATCH] compiler: allow to use multiple underscores in func arguments

It should still be present in the argument array in VM so just don't
save them in the map.

Signed-off-by: Evgeniy Stratonikov <evgeniy@nspcc.ru>
---
 pkg/compiler/function_call_test.go | 11 +++++++++++
 pkg/compiler/vars.go               |  7 +++++++
 2 files changed, 18 insertions(+)

diff --git a/pkg/compiler/function_call_test.go b/pkg/compiler/function_call_test.go
index 60935cbbe..fb118cffd 100644
--- a/pkg/compiler/function_call_test.go
+++ b/pkg/compiler/function_call_test.go
@@ -313,3 +313,14 @@ func TestJumpOptimize(t *testing.T) {
 		require.Equal(t, b[mi.Range.End], byte(opcode.RET))
 	}
 }
+
+func TestFunctionUnusedParameters(t *testing.T) {
+	src := `package foo
+	func add13(a int, _ int, _1 int, _ int) int {
+		return a + _1
+	}
+	func Main() int {
+		return add13(1, 10, 100, 1000)
+	}`
+	eval(t, src, big.NewInt(101))
+}
diff --git a/pkg/compiler/vars.go b/pkg/compiler/vars.go
index a12aa1459..b0b92496c 100644
--- a/pkg/compiler/vars.go
+++ b/pkg/compiler/vars.go
@@ -2,6 +2,7 @@ package compiler
 
 import (
 	"go/ast"
+	"strconv"
 )
 
 type varScope struct {
@@ -70,6 +71,12 @@ func (c *varScope) newVariable(t varType, name string) int {
 	case varLocal:
 		return c.newLocal(name)
 	case varArgument:
+		if name == "_" {
+			// See #2204. This name won't actually be referenced.
+			// This approach simplifies argument allocation and
+			// makes debugging easier.
+			name = "%_" + strconv.FormatUint(uint64(len(c.arguments)), 10)
+		}
 		_, ok := c.arguments[name]
 		if ok {
 			panic("argument is already allocated")