Properly, contracts are now looked up via <source>:<contract> identifiers
called "fully qualified names." As a modicum of backward-compatibility,
failure on a lookup is now backed up by seeing if the ":" exists at all,
and if it doesn't, then the known contracts are scanned for any matching
contract name.
The library name clash checker throws errors when two libraries of the
same name are spotted. In a previous commit, this function was
rewritten to use fully-qualified names instead, which makes it redundant
to the checker for multiply-declared identifiers. Since it no longer
serves a clear purpose, the function is being dropped.
Using libraries leaves behind a library link reference in the binary
which the linker must later resolve. These link references were still
being generated by name and not by fully-qualified name. This would
lead to a link-time collision between two libraries having the same
name but in different source units.
This change changes linker symbols over to fully-qualified names,
which resolves that issue. This does potentially introduce a new
problem, which is that linker symbols appear to be limited to 36
characters and are truncated. Storing paths extends the average
symbol size, and it would be great if truncation was from the tail
rather than the head.
Because contracts are uniquely identified by their source unit, there
is no need for a unique error for this; it's actually covered by the
checker for double-declaration of identifiers.
Throwing a CompilerError on multiple contract definition violates the
expectations of the test suite, which thinks that compile() will
return false if the code can't compile. This brings contract
collision reporting in line with most of the other errors.
A large number of tests compile contracts while passing in an empty
string for the source name. This leads to it being keyed by the name
":<contract>", while the tests try to look it up under the name
"<contract>". This change resolves that issue by dropping the ':' in
cases where there is, effectively, no source file to prepend anyway.
