From b1a398cf0f04ac911be204d3c0ee001a94621683 Mon Sep 17 00:00:00 2001
From: Dan Scales <danscales@google.com>
Date: Mon, 10 May 2021 10:17:51 -0700
Subject: [PATCH] [dev.typeparams] cmd/compile:  add import/export of calls to
 builtin functions

For generic functions, we have to leave the builtins in OCALL form,
rather than transform to specific ops, since we don't know the exact
types involved. Allow export/import of builtins in OCALL form.

Added new export/import test mapimp.go.

Change-Id: I571f8eeaa13b4f69389dbdb9afb6cc61924b9bf2
Reviewed-on: https://go-review.googlesource.com/c/go/+/321750
Trust: Dan Scales <danscales@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
---
 src/cmd/compile/internal/typecheck/iexport.go | 10 +++++++
 src/cmd/compile/internal/typecheck/iimport.go |  4 +++
 test/typeparam/mapimp.dir/a.go                | 15 ++++++++++
 test/typeparam/mapimp.dir/main.go             | 28 +++++++++++++++++++
 test/typeparam/mapimp.go                      |  7 +++++
 5 files changed, 64 insertions(+)
 create mode 100644 test/typeparam/mapimp.dir/a.go
 create mode 100644 test/typeparam/mapimp.dir/main.go
 create mode 100644 test/typeparam/mapimp.go

diff --git a/src/cmd/compile/internal/typecheck/iexport.go b/src/cmd/compile/internal/typecheck/iexport.go
index d125dadd88..802a8c3839 100644
--- a/src/cmd/compile/internal/typecheck/iexport.go
+++ b/src/cmd/compile/internal/typecheck/iexport.go
@@ -1579,6 +1579,16 @@ func (w *exportWriter) expr(n ir.Node) {
 		// We don't need a type here, as the type will be provided at the
 		// declaration of n.
 		w.op(ir.ONAME)
+
+		// This handles the case where we haven't yet transformed a call
+		// to a builtin, so we must write out the builtin as a name in the
+		// builtin package.
+		isBuiltin := n.BuiltinOp != ir.OXXX
+		w.bool(isBuiltin)
+		if isBuiltin {
+			w.string(n.Sym().Name)
+			break
+		}
 		w.localName(n)
 
 	// case OPACK, ONONAME:
diff --git a/src/cmd/compile/internal/typecheck/iimport.go b/src/cmd/compile/internal/typecheck/iimport.go
index 3b725a226c..39b5ab09da 100644
--- a/src/cmd/compile/internal/typecheck/iimport.go
+++ b/src/cmd/compile/internal/typecheck/iimport.go
@@ -1184,6 +1184,10 @@ func (r *importReader) node() ir.Node {
 		return n
 
 	case ir.ONAME:
+		isBuiltin := r.bool()
+		if isBuiltin {
+			return types.BuiltinPkg.Lookup(r.string()).Def.(*ir.Name)
+		}
 		return r.localName()
 
 	// case OPACK, ONONAME:
diff --git a/test/typeparam/mapimp.dir/a.go b/test/typeparam/mapimp.dir/a.go
new file mode 100644
index 0000000000..6835e214b8
--- /dev/null
+++ b/test/typeparam/mapimp.dir/a.go
@@ -0,0 +1,15 @@
+// Copyright 2021 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
+
+// Map calls the function f on every element of the slice s,
+// returning a new slice of the results.
+func Mapper[F, T any](s []F, f func(F) T) []T {
+        r := make([]T, len(s))
+        for i, v := range s {
+                r[i] = f(v)
+        }
+        return r
+}
diff --git a/test/typeparam/mapimp.dir/main.go b/test/typeparam/mapimp.dir/main.go
new file mode 100644
index 0000000000..4d4a4d9eb0
--- /dev/null
+++ b/test/typeparam/mapimp.dir/main.go
@@ -0,0 +1,28 @@
+// Copyright 2021 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"
+	"fmt"
+	"reflect"
+	"strconv"
+)
+
+func main() {
+	got := a.Mapper([]int{1, 2, 3}, strconv.Itoa)
+	want := []string{"1", "2", "3"}
+	if !reflect.DeepEqual(got, want) {
+		panic(fmt.Sprintf("got %s, want %s", got, want))
+	}
+
+	fgot := a.Mapper([]float64{2.5, 2.3, 3.5}, func(f float64) string {
+		return strconv.FormatFloat(f, 'f', -1, 64)
+	})
+	fwant := []string{"2.5", "2.3", "3.5"}
+	if !reflect.DeepEqual(fgot, fwant) {
+		panic(fmt.Sprintf("got %s, want %s", fgot, fwant))
+	}
+}
diff --git a/test/typeparam/mapimp.go b/test/typeparam/mapimp.go
new file mode 100644
index 0000000000..76930e5e4f
--- /dev/null
+++ b/test/typeparam/mapimp.go
@@ -0,0 +1,7 @@
+// rundir -G=3
+
+// Copyright 2021 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 ignored