deno: 🐛 `deno coverage` line and branch counts are incorrect

I’m getting some broken coverage results.

For the code:

export function f(b: boolean) {
        var result;
        if (b) {
                result = true;
        } else {
                result = false;
        }
        return result;
}

as a Deno script (from the repo https://github.com/rivy-t/cover-deno):

C:>deno test --unstable -A --coverage=coverage && deno coverage --unstable coverage --lcov
...
SF:C:\Users\Roy\OneDrive\Projects\deno\dexter\repo.t-cover-deno\src\mod.ts
FN:2,f
FNDA:4,f
FNF:1
FNH:1
BRDA:4,1,0,2
BRF:1
BRH:1
DA:1,2
DA:2,6
DA:3,6
DA:4,8
DA:5,8
DA:6,8
DA:7,6
DA:8,6
DA:9,2
LH:9
LF:9
end_of_record

vs the same code as ESM, using nyc/ava (from https://github.com/rivy-t/cover-esm):

C:>npm i --silent && npx nyc --silent ava && npx nyc report --reporter=text-lcov
...
TN:
SF:src\esm.js
FN:1,f
FNF:1
FNH:1
FNDA:2,f
DA:3,2
DA:4,1
DA:6,1
DA:8,2
LF:4
LH:4
BRDA:3,0,0,1
BRDA:3,0,1,1
BRF:2
BRH:2
end_of_record

Specifically, the Deno branch coverage is incorrect; the line coverage has odd counts, off-by-one’s, and, arguably, counts non-executing lines.