Do not materialise X in [X; 0] when X is unsizing a const#145277

dingxiangfei2009 wants to merge 2 commits intorust-lang:masterrust-lang/rust:masterfrom

dingxiangfei2009:fold-coercion-into-constdingxiangfei2009/rust:fold-coercion-into-constCopy head branch name to clipboard