Blocks can yield a value: last expression statement is the result.
Match arms accept block bodies, so multi-statement arms work:
match n {
1 => { let a = 10; a + 1 },
_ => 0
}
Bootstrap: lowerBlock(asExpr) lifts the trailing skExpr. Selfhost: parse
{...} as ekBlock, emit __blk_N yield temps (retTypeKind -2), and treat
only non-empty strValue as match/block yield. Nested enum/struct pattern
bindings recurse in both compilers.
Example: match_block.bux. Selfhost-loop remains binary-identical.
