[dev.typeparams] cmd/compile/internal/types2: introduce type set abstraction for interfaces

With this change, interfaces are "completed" on-demand, when needed,
and the respective information (set of all methods, type constraints)
is recorded in a new typeSet data structure.

As a consequence, interfaces don't need to be explicitly completed
anymore and (internal) uses of interfaces have become much simpler.

This change also introduces a new field Interface.complete to indicate
that all methods and embedded elements have been set up. This prevent
the computation and recording (!) of a partial type set for erroneous
programs (if we compute the partial type set and store it, subsequent
type set accesses use the wrong type set which may lead to follow-on
errors).

Change-Id: I1ffc907f7d0fb93b3e987fe5ff9c6fa5cae00d7f
Reviewed-on: https://go-review.googlesource.com/c/go/+/329309
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/src/cmd/compile/internal/types2/builtins.go b/src/cmd/compile/internal/types2/builtins.go
index 8f2d849ef5..ffe872e7ab 100644
--- a/src/cmd/compile/internal/types2/builtins.go
+++ b/src/cmd/compile/internal/types2/builtins.go
@@ -783,7 +783,7 @@ func (check *Checker) applyTypeFunc(f func(Type) Type, x Type) Type {
 		tpar := NewTypeName(nopos, check.pkg, "<type parameter>", nil)
 		ptyp := check.NewTypeParam(tpar, 0, &emptyInterface) // assigns type to tpar as a side-effect
 		tsum := newUnion(rtypes, tildes)
-		ptyp.bound = &Interface{allMethods: markComplete, allTypes: tsum}
+		ptyp.bound = &Interface{complete: true, tset: &TypeSet{types: tsum}}
 
 		return ptyp
 	}