Why does an array of mat4 produce an error in Xcode 11?

I'm trying to convert an app from Swift 2 to Swift 5 with Xcode 8, 10, & 11. The code compiles and runs on Xcode 11, but an error occurs when I attempt to run following GLSL code:

mat4 mats[4] = mat4[4](
    matA, matB, matC, matD

The error message is

program_source:3520:20: error: unexpected type name 'float4x4': expected expression float4x4 mats[4] = float4x4 [4](

The shader works as expected when compiled with Xcode 7, but, apparently, an array of mat4 is not allowed in Xcode 11. I can't find anything that says that the latest GLSL doesn't allow this. Does any know why this code doesn't compile?