Rich Kadel 7225f66887 Adds two source span utility functions used in source-based coverage ... `span.is_empty()` - returns true if `lo()` and `hi()` are equal. This is not only a convenience, but makes it clear that a `Span` can be empty (that is, retrieving the source for an empty `Span` will return an empty string), and codifies the (otherwise undocumented--in the rustc_span package, at least) fact that `Span` is a half-open interval (where `hi()` is the open end). `source_map.lookup_file_span()` - returns an enclosing `Span` representing the start and end positions of the file enclosing the given `BytePos`. This gives developers a clear way to quickly determine if any any other `BytePos` or `Span` is also from the same file (for example, by simply calling `file_span.contains(span)`). This results in much simpler code and is much more runtime efficient compared with the obvious alternative: calling `source_map.lookup_line()` for any two `Span`'s byte positions, handle both arms of the `Result` (both contain the file), and then compare files. It is also more efficient than the non-public method `lookup_source_file_idx()` for each `BytePos`, because, while comparing the internal source file indexes would be efficient, looking up the source file index for every `BytePos` or `Span` to be compared requires a binary search (worst case performance being O(log n) for every lookup). `source_map.lookup_file_span()` performs the binary search only once, to get the `file_span` result that can be used to compare to any number of other `BytePos` or `Span` values and those comparisons are always O(1).		2020-08-31 18:41:57 -07:00
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src	Adds two source span utility functions used in source-based coverage	2020-08-31 18:41:57 -07:00
Cargo.toml	mv compiler to compiler/	2020-08-30 18:45:07 +03:00