Bug 10437 – Warnings for unused private imports

The compiler should output warnings, if the source code contains imports, which are not used and can be removed. Example: For debugging the following private imports were used, but now the module does not contain any writeln or text call anymore, but parse is used. private import std.stdio; private import std.conv: text, parse; The compiler should print warnings like: foo.d(3): Warning: unused private import std.stdio; should be deleted foo.d(4): Warning: unused private import std.conv: text; should be deleted This has been discussed together with other unused stuff, but there seems to be no conclusion in the thread. http://forum.dlang.org/thread/[email protected] This enhancement helps to keep a code base clean. Less imports might reduce compile times.

What will occur with template function? import std.conv : to; T convert(T, S)(S src) { return to!T(src); } void main() {} // template function convert is not instantiated. In this case, imported std.conv is unused then compiler might warn it. Is this right?

This warning should at best be a separate switch (or we should add customization to the -w switch like we have with -transition). I dislike chatty compilers which complain about every single little nuisance.

(In reply to comment #1) > What will occur with template function? > > import std.conv : to; > > T convert(T, S)(S src) > { > return to!T(src); > } > > void main() {} > // template function convert is not instantiated. > > In this case, imported std.conv is unused then compiler might warn it. Is this > right? I think the question is misleading. The actual question is how clever the analysis is. Call-graph information provides a similar scenario: import std.stdio; void foo() { writeln("foo"); } void main () {} // foo is never called In such scenarios, deleting a statement might declare a whole chain (actually DAG) of (template or normal) functions unused. It is a question of taste, if the user should be flooded with warnings in this case.

(In reply to comment #3) > I think the question is misleading. The actual question is how clever the > analysis is. Call-graph information provides a similar scenario: > > import std.stdio; > > void foo() { > writeln("foo"); > } > > void main () {} > // foo is never called > > In such scenarios, deleting a statement might declare a whole chain (actually > DAG) of (template or normal) functions unused. It is a question of taste, if > the user should be flooded with warnings in this case. It's impossible to do that strictly with templates. Let's try to show more suitable case. import std.conv; import std.stdio; auto call(string name, A...)(A args) { return mixin(name~"(args)"); } Until 'call' template function is instantiated, compiler cannot determine which import declaration is actually unused.

Walter is strongly against warnings. The functionality that is being asked for could be implemented by a third party tool. Closing as WONTFIX.