spurious type errors involving maps

[johnw42]

When compiling this code (with --language_in=ES6_STRICT)...

/**
 * @param {Map<KEY,VALUE>} map
 * @template KEY, VALUE
 */
const foo = function(map) {
};

/**
 * @param {Map<string, number>} map
 */
const bar = function(map) {
  foo(map);
};

...I get this warning:

test.js:12: WARNING - actual parameter 1 of foo does not match formal parameter
found   : (Map<string,number>|null)
required: (Map<(number|string),(number|string)>|null)
  foo(map);

[dimvar]

Thanks for the report.

Looks like the bug happens because of this line in the definition of Map:
@implements {Iterable<!Array<KEY|VALUE>>}

When I define my own class that doesn't implement Iterable, it works as expected. If my class implements it, the spurious warnings happen. Example.

For the record, this works as expected in the new type checker, you may want to try it out.
https://github.com/google/closure-compiler/wiki/Using-NTI-(new-type-inference)