[dev.typealias] cmd/compile: export/import test cases for type aliases

Plus a few minor changes.

For #18130.

Change-Id: Ica6503fe9c888cc05c15b46178423f620c087491
Reviewed-on: https://go-review.googlesource.com/35233
Reviewed-by: Alan Donovan <adonovan@google.com>

3 files changed, 93 insertions, 0 deletions

diff --git a/test/alias3.dir/a.go b/test/alias3.dir/a.go
new file mode 100644
index 0000000000..09b3408d16
--- /dev/null
+++ b/test/alias3.dir/a.go
@@ -0,0 +1,42 @@
+// Copyright 2017 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.
+
+package a
+
+import "go/build"
+
+type (
+	Float64 = float64
+	Rune    = rune
+)
+
+type (
+	Int       int
+	IntAlias  = Int
+	IntAlias2 = IntAlias
+	S         struct {
+		Int
+		IntAlias
+		IntAlias2
+	}
+)
+
+type (
+	Context = build.Context
+)
+
+type (
+	I1 interface {
+		M1(IntAlias2) Float64
+		M2() Context
+	}
+
+	I2 = interface {
+		M1(Int) float64
+		M2() build.Context
+	}
+)
+
+var i1 I1
+var i2 I2 = i1
diff --git a/test/alias3.dir/b.go b/test/alias3.dir/b.go
new file mode 100644
index 0000000000..8a86cc0643
--- /dev/null
+++ b/test/alias3.dir/b.go
@@ -0,0 +1,26 @@
+// Copyright 2017 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.
+
+package b
+
+import (
+	"./a"
+	. "go/build"
+)
+
+func F(x float64) a.Float64 {
+	return x
+}
+
+type MyContext = Context // = build.Context
+
+var C a.Context = Default
+
+type S struct{}
+
+func (S) M1(x a.IntAlias) float64 { return a.Float64(x) }
+func (S) M2() Context             { return Default }
+
+var _ a.I1 = S{}
+var _ a.I2 = S{}
diff --git a/test/alias3.dir/c.go b/test/alias3.dir/c.go
new file mode 100644
index 0000000000..161d5934c2
--- /dev/null
+++ b/test/alias3.dir/c.go
@@ -0,0 +1,25 @@
+// Copyright 2017 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.
+
+package main
+
+import (
+	"./a"
+	"./b"
+)
+
+func main() {
+	var _ float64 = b.F(0)
+	var _ a.Rune = int32(0)
+
+	// embedded types can have different names but the same types
+	var s a.S
+	s.Int = 1
+	s.IntAlias = s.Int
+	s.IntAlias2 = s.Int
+
+	// aliases denote identical types across packages
+	var c a.Context = b.C
+	var _ b.MyContext = c
+}