casting - GLSL implicit int to float error yielded at "float to float"…?

Question

The following line in my fragment-shader…</p>

gl_FragColor.r = curPosition.x;

raises warning C7011: implicit cast from "int" to "float" but curPosition is defined as vec3 (so it is a float) and gl_FragColor.r is … well … a float. so… what's the problem?