From 2a1d23d926d00cf24d0ae5adb2c34d7982e003dd Mon Sep 17 00:00:00 2001
From: Hajime Hoshi <hajimehoshi@gmail.com>
Date: Wed, 26 Apr 2023 22:07:40 +0900
Subject: [PATCH] internal/shader: bug fix: panic when an assignment mismatch
 happens

Closes #2654
---
 internal/shader/stmt.go        |  9 +++++++++
 internal/shader/syntax_test.go | 16 ++++++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/internal/shader/stmt.go b/internal/shader/stmt.go
index 1196f7689..e25ee8f28 100644
--- a/internal/shader/stmt.go
+++ b/internal/shader/stmt.go
@@ -639,6 +639,15 @@ func (cs *compileState) assign(block *block, fname string, pos token.Pos, lhs, r
 			}
 			stmts = append(stmts, ss...)
 
+			if len(l) != len(r) {
+				if len(r) == 0 {
+					cs.addError(pos, fmt.Sprintf("right-hand side (no value) used as value"))
+				} else {
+					cs.addError(pos, fmt.Sprintf("assignment mismatch: %d variables but the right-hand side has %d values", len(l), len(r)))
+				}
+				return nil, false
+			}
+
 			if l[0].Type == shaderir.Blank {
 				continue
 			}
diff --git a/internal/shader/syntax_test.go b/internal/shader/syntax_test.go
index 93327a738..290da0317 100644
--- a/internal/shader/syntax_test.go
+++ b/internal/shader/syntax_test.go
@@ -3122,3 +3122,19 @@ func Fragment(position vec4, texCoord vec2, color vec4) vec4 {
 		}
 	}
 }
+
+// Issue #2654
+func TestOmittedReturnType(t *testing.T) {
+	if _, err := compileToIR([]byte(`package main
+
+func foo(x vec2) {
+	x = bar(x)
+	_ = x
+}
+
+func bar(x vec2) {
+	return x
+}`)); err == nil {
+		t.Error("compileToIR must return an error but did not")
+	}
+}