issue with replacement of arguments[x] when parameter is redefined about terser HOT 5 CLOSED

@phazei Cannot reproduce an incorrect result. Could you add one or more console.log() statements to your example to demonstrate the program producing a wrong result when minified?

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Here's a different test case that produces an incorrect result when minified:

$ bin/uglifyjs -V
terser 3.7.6

$ cat issue-t58.js 
function f(x){
    console.log(x, arguments[0]);
    x = 2;
    console.log(x, arguments[0]);
    arguments[0] = 3;
    console.log(x, arguments[0]);
}
f();
f(1);

expected:

$ cat issue-t58.js | node
undefined undefined
2 undefined
2 3
1 1
2 2
3 3

actual:

$ cat issue-t58.js | bin/uglifyjs -bc | node
undefined undefined
2 2
2 2
1 1
2 2
3 3

Bug workaround - disable the arguments compress option:

$ cat issue-t58.js | bin/uglifyjs -bc arguments=false | node
undefined undefined
2 undefined
2 3
1 1
2 2
3 3

We may elect to have the arguments option disabled in terser by default as well.

I'd still like to see the example in the top post altered to produce incorrect output when run in the event that it is a different issue.

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Turns out "use strict"; is necessary to provide the proper issue error I found out after a bit more testing.

I've updated the code in the op to reflect that as well as console.log'ing

Also just a note: I was using gulp-uglify which was using uglify-js 2.8.29 and that didn't have the issue. I just recently converted to gulp-uglify-es which uses the latest terser version. While switching over only required changing the 'require()' package name, this seems to be the only issue that arose.

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@phazei Thanks for the repro.

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uglify-js has the same problem. Reported upstream: mishoo/UglifyJS#3192

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