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