[dev.typeparams] cmd/compile/internal/importer, types2: initial check-in of types2 and importer

This is a copy of the importer and types2 (unreviewed) prototype version
excluding the testdata directory containing tests (see below). Each file
is marked with the comment

// UNREVIEWED

on the first line. The plan is to check in this code wholesale (it runs and
passes all tests) and then review the code file-by-file via subsequent CLs
and remove the "// UNREVIEWED" comments as we review the files.

Since most tests are unchanged from the original go/types, the next CL will
commit those tests as they don't need to be reviewed again. (Eventually we
may want to factor them out and share them from a single place, e.g. the
test directory.)

The existing file fmtmap_test.go was updated.

Change-Id: I9bd0ad1a7e7188b501423483a44d18e623c0fe71
Reviewed-on: https://go-review.googlesource.com/c/go/+/263624
Trust: Robert Griesemer <gri@golang.org>
Trust: Keith Randall <khr@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

1 files changed, 36 insertions, 0 deletions

diff --git a/src/cmd/compile/internal/types2/importer_test.go b/src/cmd/compile/internal/types2/importer_test.go
new file mode 100644
index 0000000000..90476c4269
--- /dev/null
+++ b/src/cmd/compile/internal/types2/importer_test.go
@@ -0,0 +1,36 @@
+// UNREVIEWED
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file implements the (temporary) plumbing to get importing to work.
+
+package types2_test
+
+import (
+	gcimporter "cmd/compile/internal/importer"
+	"cmd/compile/internal/types2"
+	"io"
+)
+
+func defaultImporter() types2.Importer {
+	return &gcimports{
+		packages: make(map[string]*types2.Package),
+	}
+}
+
+type gcimports struct {
+	packages map[string]*types2.Package
+	lookup   func(path string) (io.ReadCloser, error)
+}
+
+func (m *gcimports) Import(path string) (*types2.Package, error) {
+	return m.ImportFrom(path, "" /* no vendoring */, 0)
+}
+
+func (m *gcimports) ImportFrom(path, srcDir string, mode types2.ImportMode) (*types2.Package, error) {
+	if mode != 0 {
+		panic("mode must be 0")
+	}
+	return gcimporter.Import(m.packages, path, srcDir, m.lookup)
+}