When compiling JSL shaders to HLSL6, following warning is emitted whenever a paint() function is used (example):
(...)\jfx-sandbox\rt\modules\javafx.graphics\build\gensrc\jsl-prism\com\sun\prism\d3d12\hlsl6\Solid_LinearGradient_REFLECT.hlsl:81:15: warning: implicit truncation of vector type [-Wconversion]
color = paint(pixcoord) * jsl_vertexColor;

Above warning does not necessarily affect the shader code or compilation, but should be fixed regardless during cleanup.