* feat: add support for named output variables
Function output parameters are located at the start of the function
frame, uninitialized, as they could be only set through return
statements.
Supporting named output variables requires to:
- identify and allocate symbols corresponding to output names:
done at ident parsing, with the funcRet() helper,
- compute the location of output name in the frame:
done with retRank() helper,
- initialize the frame entry with the zero value of symbol type,
as the symbol can be accessed and written at multiple times,
and return not setting the variable (opposite to unnamed).
Done with frameType() helper, which now takes into account
output parameters.
* refactor: simplify memory management
Perform function frame analysis at pre-order, instead of post-order, to
initialize memory frame, and track value types. Remove all operation
involving unitialized types. Frame memory layout is now build
incrementally, instead of having to perform dedicated tree walks on AST.
Type category `UnsetT` is renamed in `NilT`.
Catch invalid use of untyped nil in `:=` expression.
Convert nil to output parameter type when used in `return` expression.
Improve and add relevant unit tests.
Eval returns the value of the root node of AST, so ensure
that node values are propagated back to ExprStmt and BlockStmt,
which should be sufficient to handle evaluation of simple
statements.
Change the way imported binary variables are imported, from
`reflect.ValueOf(val)` to `reflect.ValueOf(&val).Elem()`, to allow these
variables to be set from the interpreter.
Regenerate stdlib packages accordingly.
Ensure that binary value is forwarded if it exists.
Add tests.
The recovered state is stored in `Frame`, and captured in `runCfg()`.
`assign()` has been modified to set handle `interface{}` type (not
possible with `reflect`.
* style: fix warnings from golangci-lint printed by `make check`
* style: err assign in if block when possible. Better use of switch/case
* style: err assign in if block when possible
* ast: improve error handling
* ast: handle select
* dyngo: set filename of executed script
* cfg: improve error reporting
* Implement select for receiving channels
* feat(select): add support for sending channels in case clauses
* test: improve tests on select
* feat(select): add support for "default" case
