internal/shader: bug fix: operators between vec/mat and float should work

Closes #1963

internal/shader/stmt.go

@@ -108,6 +108,13 @@ func (cs *compileState) parseStmt(block *block, fname string, stmt ast.Stmt, inP
 						cs.addError(stmt.Pos(), fmt.Sprintf("invalid operation: mismatched types %s and %s", lts[0].String(), rts[0].String()))
 						return nil, false
 					}
+				case shaderir.Vec2, shaderir.Vec3, shaderir.Vec4, shaderir.Mat2, shaderir.Mat3, shaderir.Mat4:
+					if rts[0].Main == shaderir.Float || rhs[0].Const != nil {
+						// ok
+					} else {
+						cs.addError(stmt.Pos(), fmt.Sprintf("invalid operation: mismatched types %s and %s", lts[0].String(), rts[0].String()))
+						return nil, false
+					}
 				default:
 					cs.addError(stmt.Pos(), fmt.Sprintf("invalid operation: mismatched types %s and %s", lts[0].String(), rts[0].String()))
 					return nil, false

shader_test.go

@@ -1459,3 +1459,46 @@ func Fragment(position vec4, texCoord vec2, color vec4) vec4 {
 		t.Errorf("error must be non-nil but was nil")
 	}
 }
+
+// Issue #1963
+func TestShaderOperatorVecAndNumber(t *testing.T) {
+	if _, err := ebiten.NewShader([]byte(`package main
+
+func Fragment(position vec4, texCoord vec2, color vec4) vec4 {
+	a := vec2(1)
+	a += 2
+	return a.xxyy
+}`)); err != nil {
+		t.Error(err)
+	}
+
+	if _, err := ebiten.NewShader([]byte(`package main
+
+func Fragment(position vec4, texCoord vec2, color vec4) vec4 {
+	a := vec2(1)
+	a += 2.1
+	return a.xxyy
+}`)); err != nil {
+		t.Error(err)
+	}
+
+	if _, err := ebiten.NewShader([]byte(`package main
+
+func Fragment(position vec4, texCoord vec2, color vec4) vec4 {
+	a := vec2(1)
+	a %= 2
+	return a.xxyy
+}`)); err == nil {
+		t.Errorf("error must be non-nil but was nil")
+	}
+
+	if _, err := ebiten.NewShader([]byte(`package main
+
+func Fragment(position vec4, texCoord vec2, color vec4) vec4 {
+	a := vec2(1)
+	a %= 2.1
+	return a.xxyy
+}`)); err == nil {
+		t.Errorf("error must be non-nil but was nil")
+	}
+}