Language issues

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Like any programming language, D is not perfect. This page lists some potential problems that have been brought up and debated throughout the language's history. Fixing these is not straight-forward or may not justify breaking backwards-compatibility. As of the moment of writing this, there are no plans for a major revision of D which would allow such breaking changes, but this list may also be useful for other programming languages which wish to learn from D's experience.

See also: Language design discussions


Design of properties has been an oft-discussed topic. This language feature has evolved throughout D's history (e.g. the addition and removal of the -property switch). There are numerous DIPs with proposals on improving the design:

See also:

Unicode and ranges

D's ranges currently treat strings in a special way: they present them as a range of code points, thus implicitly performing UTF decoding. Algorithms that do not require working with decoded code points, and which would gain a performance advantage by treating the input as a range of code units (or an array of code units), must incorporate D strings as a special case. This approach complicates the implementation by some degree, and only solves a certain subset of problems for a subset of written languages.

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Signed/unsigned comparisons

(What's the status of this? Issue 259 is open and has an open pull request.)

Null References

{Please add summary}

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Virtual by default

In D, methods are virtual by default. Although this approach does have benefits from the point of view of extensibility, it has been criticized that this default incurs a considerable performance impact and harms forward compatibility in user code, unless explicitly disabled everywhere as appropriate using the final keyword.

Although at one point Walter Bright intended to change the default (see Issue 11616 and DIP51), ultimately this proposal has been rejected.

Default constructors

D does not support custom default constructors for value types: attempting to declare a struct constructor without any arguments is an error. The rationale for this limitation is to allow any type to have a known constant default value (.init property). This is unlike C++, where structs and classes can have default constructors, which allow executing custom code at the point of a variable's declaration.

D's restriction prevents implementing certain C++ patterns, and requires users to rely on conventions for factory functions.