dmd.aliasthis

Implements the alias this symbol.

Specification: Alias This

Authors

Walter Bright

License

Boost License 1.0

Source: aliasthis.d

Documentation: https://dlang.org/phobos/dmd_aliasthis.html

Coverage: https://codecov.io/gh/dlang/dmd/src/master/src/dmd/aliasthis.d

  • AliasThis

    Declaration

    class AliasThis: dmd.dsymbol.Dsymbol;

    alias ident this;

    • sym

      Declaration

      Dsymbol sym;

      The symbol this alias this resolves to

    • isDeprecated_

      Declaration

      bool isDeprecated_;

      Whether this alias this is deprecated or not

  • resolveAliasThis

    Declaration

    Expression resolveAliasThis(Scope* sc, Expression e, bool gag = false, bool findOnly = false);

    Find the alias this symbol of e's type.

    Parameters

    Scope* sc

    context

    Expression e

    expression forming the this

    bool gag

    do not print errors, return null instead

    bool findOnly

    don't do further processing like resolving properties, i.e. just return plain dotExp() result.

    Return Value

    Expression that is e.aliasthis

  • checkDeprecatedAliasThis

    Declaration

    bool checkDeprecatedAliasThis(AliasThis at, const ref Loc loc, Scope* sc);

    Check if an alias this is deprecated

    Discussion

    Usually one would use expression.checkDeprecated(scope, aliasthis) to check if expression uses a deprecated aliasthis, but this calls toPrettyChars which lead to the following message: "Deprecation: alias this fullyqualified.aggregate.__anonymous is deprecated"

    Parameters

    AliasThis at

    The AliasThis object to check

    Loc loc

    Loc of the expression triggering the access to at

    Scope* sc

    Scope of the expression (deprecations do not trigger in deprecated scopes)

    Return Value

    Whether the alias this was reported as deprecated.

  • isRecursiveAliasThis

    Declaration

    bool isRecursiveAliasThis(ref Type att, Type t);

    Check and set 'att' if 't' is a recursive 'alias this' type

    Discussion

    The goal is to prevent endless loops when there is a cycle in the alias this chain. Since there is no multiple alias this, the chain either ends in a leaf, or it loops back on itself as some point.

    Example: S0 -> (S1 -> S2 -> S3 -> S1)

    S0 is not a recursive alias this, so this returns false, and a rewrite to S1 can be tried. S1 is a recursive alias this type, but since att is initialized to null, this still returns false, but att1 is set to S1. A rewrite to S2 and S3 can be tried, but when we want to try a rewrite to S1 again, we notice att == t, so we're back at the start of the loop, and this returns true.

    Parameters

    Type att

    type reference used to detect recursion. Should be initialized to null.

    Type t

    type of 'alias this' rewrite to attempt

    Return Value

    false if the rewrite is safe, true if it would loop back around