Undetected unreachable code

These are obvious mistakes.

TypeScript Version: 3.7.x-dev.20191221

Search Terms:

Code

declare const a: boolean;
(() => {
    if (a) return;
    if (a) {
        return; // Unreachable
    }
});
while (1) {
    if (a) break;
    if (a) {
        break; // Unreachable
    }
}

Expected behavior:
Detect unreachable code.
Actual behavior:
not detected.
Playground Link: http://www.typescriptlang.org/play/index.html?ts=3.8.0-dev.20191221#code/CYUwxgNghgTiAEYD2A7AzgF3lAXPARkkhCFCgNwCwAUABS0CU8AvAHzwDeN8P8AlgDN4tKEzgYArjArdeg4aM6zevcVIrwA9JvgBVFHChgAFlHwll8AL40rDKtQDuxviWEBGJl2or5IpviGANYOvkL+Sj4qvIGkIVo6+oYmZhZRPDbUVkA

Related Issues:

Start with the provided Playground reproduction using TypeScript 3.7.x-dev.20191221 or a current nightly build, and compare diagnostics for the repeated if statements and while-loop branches. Trace the existing unreachable-code diagnostic behavior for these examples and add coverage showing that the marked statements are reported without changing valid control-flow diagnostics.