Variable shadowing bug in generated JavaScript code

[jeromesimeon]

For the JavaScript target, when using operators, the compiler produces JavaScript code with erroneous variable shadowing.

This can be seen on the following unit test.
inlinetest.zip

To test:

bash-3.2$ ergorun ./model.cto ./logic.ergo --contractname org.accordproject.inlinetest.InlineTest --contract ./contract.json --request ./request1.json --state ./state.json 
12:35:12 - info:
{
  "response": {
    "x": 10,
    "y": "2018-11-01T04:00:00.000Z",
    "$class": "org.accordproject.inlinetest.Response"
  },
  "state": {
    "$class": "org.accordproject.cicero.contract.AccordContractState",
    "stateId": "1"
  },
  "emit": []
}

Note that on test2, using a let binding you get the correct result:

bash-3.2$ ergorun ./model.cto ./logic.ergo --contractname org.accordproject.inlinetest.InlineTest --contract ./contract.json --request ./request2.json --state ./state.json 
12:35:17 - info:
{
  "response": {
    "x": 0,
    "y": "2018-11-01T04:00:00.000Z",
    "$class": "org.accordproject.inlinetest.Response"
  },
  "state": {
    "$class": "org.accordproject.cicero.contract.AccordContractState",
    "stateId": "1"
  },
  "emit": []
}

[jeromesimeon]

The issue can be seen on the generated JavaScript code:

bash-3.2$ ergoc ./model.cto ./logic.ergo 
Compiling Ergo './logic.ergo' -- creating './logic.js'

lines 121-122 of the compiled logic.js:

    var vp1 = 0.0;
    var vp1 = "2018-01-01";

so the first constant 0.0 in vp1 is over-ridden.

[jeromesimeon]

Here is a simpler inlining test which illustrate the problem on a simpler example using Ergo functions:
inlinetest.zip

Again, running it:

bash-3.2$ ergorun ./model.cto ./logic.ergo --contractname org.accordproject.inlinetest.InlineTest --contract ./contract.json --request ./request1.json --state ./state.json 
23:47:03 - info:
{
  "response": {
    "x": 10,
    "y": 22,
    "$class": "org.accordproject.inlinetest.Response"
  },
  "state": {
    "$class": "org.accordproject.cicero.contract.AccordContractState",
    "stateId": "1"
  },
  "emit": []
}

Again, compiling it with:

bash-3.2$ ergoc ./model.cto ./logic.ergo 
Compiling Ergo 'logic.ergo' -- creating 'logic.js'

lines 17-18 shows the problem:

  var vp1 = 0.0;
  var vp1 = 10.0;

[jeromesimeon]

After adding some instrumentation to print out the NNRC module during compilation, one can see that the code looks correct:

NNRC Module: 
FUNCTION: org.accordproject.inlinetest.h
#brand[org.accordproject.inlinetest.Response]([ x :
                                                let $vp1 := 0.000000 in $vp1 ]
                                              [+]
                                              [ y :
                                                let $vp1 := 10.000000
                                                in
                                                  let $vp2 := 12.000000
                                                  in $vp1 F+ $vp2 ])

Which means the issue is in the Qcert JavaScript code generation.

A couple of options to address the issue:

1. Switch to the more recent JavaScript code-generation from Qcert (i.e., implement Switch to improved JavaScript backend #191)
2. Add a global variable renaming phase before code-generation to avoid name collisions

[jeromesimeon]

Besides the fix that was implemented for the shadowing bug a few months ago, we are now using a completely new JavaScript backend which produces properly JavaScript blocks with a proof that it handles scoping properly. (See PR #732)

I'm considering this issue finally resolved and closing the issue.