[Feature] Default template arguments

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#42 2 comments 0 reactions 0 assignees View on GitHub

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Assessment

Difficulty
5/5
Estimated time
Over a week
Newbie friendliness
25/100
Issue type
Feature
Clarity
Needs clarification
Activity status
Stale
Tech stack
cpp
Domain
compilers

Research direction

The issue defines the requested default-template syntax through the Array and Optional examples, but names no source files, tests, or parser entry points. Start by locating the template parsing and type-resolution code, then identify existing tests for template arguments. Done means omitted arguments use their declared defaults while explicitly supplied arguments still override them.

Written by the indexing model from the issue text.

Description

What feature would you like to see?

Overrideable default values for template arguments like in C++.

struct Array<T = u32, auto Size = 10> {
  T data[Size];
};
How will this feature be useful to you and others?

I have a large number of "optional" structs in my patterns

struct Optional<T, U> {
    U isSome;
    if (isSome != 0) {
        T data;
    }
};

99% of the time U is a u8, but sometimes it is a u32. It would be nice to only have to specify U in the rare case rather than every time.

struct Optional<T, U = u8> {
    U isSome;
    if (isSome != 0) {
        T data;
    }
};

Optional<SomeOtherStruct> common_optional @ 0x00;
Optional<SomeOtherStruct, u32> uncommon_optional @ 0x10;
Request Type
  • I can provide a PoC for this feature or am willing to work on it myself and submit a PR
Additional context?

No response

Dominant language
C++
Stars
275
Forks
75
Avg merge
1d 22h
Merged PRs (30d)
10

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