[Issue 17067] New: D header file generation includes excess imports

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=17067

          Issue ID: 17067
           Summary: D header file generation includes excess imports
           Product: D
           Version: D2
          Hardware: x86_64
                OS: Windows
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: dhasenan at gmail.com

Consider the following module:

---
import std.stdio;

class Foo
{
    void bar()
    {
        writeln("Hello world!");
    }
}
---

While it includes a top-level import, that import isn't used in any of its
declarations.

dmd -H produces:

---
// D import file generated from 'ditest.d'
import std.stdio;
class Foo
{
    void bar();
}
---

The unneeded import is retained.

Thanks to Peaker on IRC for pointing this out -- apparently they have a project
that takes many minutes to compile, but, aside from excessive import costs,
incremental builds can finish within a couple seconds.

As an aside, it would be relatively straightforward to map all imports to
static imports in .di files, which would achieve significant savings if we made
static imports lazy.

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