We may revisit this decision in a future release. By disallowing this
for Go 1.18 we are ensuring that we don't lock in the generics design
in a place that may need to change later. (Type declarations are the
primary construct where it crucially matters what the underlying type
of a type parameter is.)
Comment out all tests that rely on this feature; add comments referring
to issue so we can find all places easily should we change our minds.
Fixes#45639.
Change-Id: I730510e4da66d3716d455a9071c7778a1e4a1152
Reviewed-on: https://go-review.googlesource.com/c/go/+/359177
Trust: Robert Griesemer <gri@golang.org>
Trust: Dan Scales <danscales@google.com>
Reviewed-by: Dan Scales <danscales@google.com>
We don't usually reformat the test directory, but all of the files in
test/typeparam are syntactically valid. I suspect the misformattings
here are because developers aren't re-installing gofmt with
-tags=typeparams, not intentionally exercising non-standard
formatting.
Change-Id: I3767d480434c19225568f3c7d656dc8589197183
Reviewed-on: https://go-review.googlesource.com/c/go/+/338093
Trust: Matthew Dempsky <mdempsky@google.com>
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
Deal with export/import of recursive generic types. This includes
typeparams which have bounds that reference the typeparam.
There are three main changes:
- Change export/import of typeparams to have an implicit "declaration"
(doDecl). We need to do a declaration of typeparams (via the
typeparam's package and unique name), because it may be referenced
within its bound during its own definition.
- We delay most of the processing of the Instantiate call until we
finish the creation of the top-most type (similar to the way we
delay CheckSize). This is because we can't do the full instantiation
properly until the base type is fully defined (with methods). The
functions delayDoInst() and resumeDoInst() delay and resume the
processing of the instantiations.
- To do the full needed type substitutions for type instantiations
during import, I had to separate out the type subster in stencil.go
and move it to subr.go in the typecheck package. The subster in
stencil.go now does node substitution and makes use of the type
subster to do type substitutions.
Notable other changes:
- In types/builtins.go, put the newly defined typeparam for a union type
(related to use of real/imag, etc.) in the current package, rather
than the builtin package, so exports/imports work properly.
- In types2, allowed NewTypeParam() to be called with a nil bound, and
allow setting the bound later. (Needed to import a typeparam whose
bound refers to the typeparam itself.)
- During import of typeparams in types2 (importer/import.go), we need
to keep an index of the typeparams by their package and unique name
(with id). Use a new map typParamIndex[] for that. Again, this is
needed to deal with typeparams whose bounds refer to the typeparam
itself.
- Added several new tests absdiffimp.go and orderedmapsimp.go. Some of
the orderemapsimp tests are commented out for now, because there are
some issues with closures inside instantiations (relating to unexported
names of closure structs).
- Renamed some typeparams in test value.go to make them all T (to make
typeparam uniqueness is working fine).
Change-Id: Ib47ed9471c19ee8e9fbb34e8506907dad3021e5a
Reviewed-on: https://go-review.googlesource.com/c/go/+/323029
Trust: Dan Scales <danscales@google.com>
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
