Rollup: Bug: Treeshaking destroys valid function contents > 0.49.0

[Havunen]

This can be reproduced by using inferno mono repo:
original issue: https://github.com/infernojs/inferno/issues/1199
repo: https://github.com/infernojs/inferno

steps to reproduce
clone repo
npm i (install latest rollup also)
npm run build
verify that file packages/inferno-mobx/dist/index.js has empty makeReactive function. Downgrading to 0.48.2 fixed the issue.

[kzc]

This alias via a logical or is tripping up rollup version 0.49.2.

Reduced repro:

$ cat t1599.js 
function foo(obj) {
    var alias = obj.prototype || obj;
    alias.prop = "PASS";
    return obj;
}
console.log(foo({}).prop || "FAIL");

```
$ cat t1599.js | node
PASS

$ bin/rollup t1599.js -f es --silent | node
FAIL

$ bin/rollup t1599.js -f es --silent
function foo(obj) {
return obj;
}
console.log(foo({}).prop || "FAIL");

Fix:
```patch
--- a/src/ast/nodes/LogicalExpression.js
+++ b/src/ast/nodes/LogicalExpression.js
@@ -16,4 +16,8 @@ export default class LogicalExpression extends Node {

                return operators[ this.operator ]( leftValue, rightValue );
        }
+
+       hasEffectsWhenMutated () {
+               return true;
+       }
 }

No test regressions.

[lukastaegert]

Thanks @Havunen for the report with easy to reproduce steps and especially @kzc for the speedy and correct analysis. This is a big oversight I am right now working on correcting. This problem does not only affect LogicalExpressions but can potentially affects other expressions as well. I will make hasEffectsWhenMutated() = true the default and will change this for nodes where this has properly been tested after the next PR.

[lukastaegert]

Should be fixed in the next released 😇