Matrix components and dot product

Question

I have the following GLSL code:

uniform mat3x3 rgb2xyz = mat3x3(
    vec3(DEFAULT_RGB2XYZ_XR, DEFAULT_RGB2XYZ_XG, DEFAULT_RGB2XYZ_XB),
    vec3(DEFAULT_RGB2XYZ_YR, DEFAULT_RGB2XYZ_YG, DEFAULT_RGB2XYZ_YB),
    vec3(DEFAULT_RGB2XYZ_ZR, DEFAULT_RGB2XYZ_ZG, DEFAULT_RGB2XYZ_ZB)
    );

vec3 RGBtoXYZ(vec3 rgb)
{
            // Works
    float X = DEFAULT_RGB2XYZ_XR * rgb.r + DEFAULT_RGB2XYZ_XG * rgb.g + DEFAULT_RGB2XYZ_XB * rgb.b;
    float Y = DEFAULT_RGB2XYZ_YR * rgb.r + DEFAULT_RGB2XYZ_YG * rgb.g + DEFAULT_RGB2XYZ_YB * rgb.b;
    float Z = DEFAULT_RGB2XYZ_ZR * rgb.r + DEFAULT_RGB2XYZ_ZG * rgb.g + DEFAULT_RGB2XYZ_ZB * rgb.b;
    return vec3(X, Y, Z);

            // Don't work
    /*float X = rgb2xyz[0][0] * rgb.r + rgb2xyz[0][1] * rgb.g + rgb2xyz[0][2] * rgb.b;
    float Y = rgb2xyz[1][0] * rgb.r + rgb2xyz[1][1] * rgb.g + rgb2xyz[1][2] * rgb.b;
    float Z = rgb2xyz[2][0] * rgb.r + rgb2xyz[2][1] * rgb.g + rgb2xyz[2][2] * rgb.b;
    return vec3(X, Y, Z);*/

            // Don't work
    /*return vec3(
        dot(rgb2xyz[0], rgb),
        dot(rgb2xyz[1], rgb),
        dot(rgb2xyz[2], rgb)
    );*/
}

The routine RGBtoXYZ have three code blocks (the last two commented). The first one work as expected, while the other commented ones does not work.

The problem is that I think they are equivalent. Why they are not?

Answer 1

I can't believe it!

The Paul-Jan edit has resolved my issue!

Simply the GLSL compiler do not emit error on matrix initialization! I can't believe it!

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I'm curious of your comments here, I'm thinking to open another question on this issue.