Rollup merge of #32710 - jonas-schievink:consider-last-semi, r=nagisa

Fix "consider removing this semicolon" help

Check last statement in a block, not the first.

Example of current weirdness: http://is.gd/w80J9h

The help was only rarely emitted, and if so, often incorrectly (see above playpen). It was basically only useful with single-statement functions.