fix Issue 11824 - A stack variable escaping problem in CTFE Phobos code
Move Expression::optimize into a visitor class
Move Expression::integralPromotions into a free function
fix Issue 12070 - Variant opCall not static

If both constructor and opCall exist, `Type()` should be handled as literal syntax for default construction.
Merge pull request #3214 from yebblies/optvisitor

[DDMD] [refactor] Move Expression::optimize into a visitor class
Move Expression::toDelegate into a free function
Merge pull request #3216 from yebblies/integralPromotions

[DDMD] [refactor] Move Expression::integralPromotions into a free function
Merge pull request #3215 from yebblies/todelegate

[DDMD] [refactor] Move Expression::toDelegate into a free function
Move Expression::isConst into a free function
fix Issue 12079 - Internal error: backend/cod4.c 358 for associative array access
fix Issue 12080 - Internal error: backend/symbol.c 1035 for invariant
Merge pull request #3224 from yebblies/isconst

[DDMD] [refactor] Move Expression::isConst into a free function
Merge pull request #3222 from 9rnsr/fix12079

[REG2.065a] Issue 12079 - Internal error: backend/cod4.c 358 for associative array access
Merge pull request #3225 from 9rnsr/fix12080

[REG2.065a] Issue 12080 - Internal error: backend/symbol.c 1035 for invariant
Merge pull request #3221 from 9rnsr/fix12070

[REG2.065a] Issue 12070 - Variant opCall not static
Merge pull request #3204 from 9rnsr/fix11824

[REG2.065a] Issue 11824 - A stack variable escaping problem in CTFE Phobos code