[Issue 19869] `PrimaryExpression` allows incorrect forms of function literals

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=19869

--- Comment #1 from Basile-z <b2.temp at gmx.com> ---
BodyStatement is probably for
https://dlang.org/spec/function.html#SpecifiedFunctionBody

There are two options:

1. The easy way, remove the rule
2. Fix the compiler to allow `FunctionContractsopt SpecifiedFunctionBody` as
subrule of FunctionLiteralBody

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