https://issues.dlang.org/show_bug.cgi?id=24548

          Issue ID: 24548
           Summary: [spec] Boolean condition conversion is not documented
           Product: D
           Version: D2
          Hardware: x86_64
                OS: Linux
            Status: NEW
          Severity: minor
          Priority: P1
         Component: dlang.org
          Assignee: nobody@puremagic.com
          Reporter: nick@geany.org

E.g. for IfStatement, the spec just says:

> Expression is evaluated. The result is converted to a boolean, using opCast!bool() if the method is defined.

That is insufficient information. It should specify which types can be converted to bool, and how.

PR incoming.

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