Catch clause identifier cannot be watched in async function

[kkeri]

Issue Type: Bug

Steps to reproduce:

1. Copy the following code into test.ts.

async function catches (f) {
  try {
    await f()
  }
  catch (e) {
    console.error(e)
  }
}
catches(() => { throw new Error() })

2. Transpile the code for ES5 target. (I used Typescript version 3.3.3)
3. Set breakpoint on the console.error(e) line.
4. Launch program, let the debugger pause at the breakpoint.

Expected behavior: if I move the cursor over the identifier e, or add a new watch, I see the value of e.

Actual behavior: I can't see the value of e. If I try to add a watch, I get e: not available.

Notes:

• If I remove await from the code, the issue doesn't occur.
• If I add watch for the identifier e_1 instead e, it works. The obvious reason is being the compiler has changed the variable name. See the relevant part of the transpiled file:

function catches(f) {
    return __awaiter(this, void 0, void 0, function () {
        var e_1;
        return __generator(this, function (_a) {
            switch (_a.label) {
                case 0:
                    _a.trys.push([0, 2, , 3]);
                    return [4 /*yield*/, f()];
                case 1:
                    _a.sent();
                    return [3 /*break*/, 3];
                case 2:
                    e_1 = _a.sent();
                    console.error(e_1);
                    return [3 /*break*/, 3];
                case 3: return [2 /*return*/];
            }
        });
    });
}

VS Code version: Code 1.31.1 (1b8e830, 2019-02-12T02:20:54.427Z)
OS version: Windows_NT x64 10.0.17134

System Info

Item	Value
CPUs	AMD FX(tm)-4100 Quad-Core Processor (4 x 3607)
GPU Status	2d_canvas: enabled checker_imaging: disabled_off flash_3d: enabled flash_stage3d: enabled flash_stage3d_baseline: enabled gpu_compositing: enabled multiple_raster_threads: enabled_on native_gpu_memory_buffers: disabled_software rasterization: enabled surface_synchronization: enabled_on video_decode: enabled webgl: enabled webgl2: enabled
Memory (System)	7.73GB (2.44GB free)
Process Argv	--disable-extensions
Screen Reader	no
VM	0%

Extensions disabled

[roblourens]

#12066

[vscodebot]

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