cmd/compile: replace calls to typecheck with transform functions

For additions, compares, and slices, create transform functions that do
just the transformations for those nodes by the typecheck package (given
that the code has been fully typechecked by types2). For nodes that have
no args with typeparams, we call these transform functions directly in
noder2. But for nodes that have args with typeparams, we have to delay
and call the tranform functions during stenciling, since we don't know
the specific types involved.

We indicate that a node still needs transformation by setting Typecheck
to a new value 3. This value means the current type of the node has been
set (via types2), but the node may still need transformation.

Had to export typcheck.IsCmp and typecheck.Assignop from the typecheck
package.

Added new tests list2.go (required delaying compare typecheck/transform
because of != compare in checkList) and adder.go (requires delaying add
typecheck/transform, since it can do addition for numbers or strings).

There are several more transformation functions needed for expressions
(indexing, calls, etc.) and several more complicated ones needed for
statements (mainly various kinds of assignments).

Change-Id: I7d89d13a4108308ea0304a4b815ab60b40c59b0a
Reviewed-on: https://go-review.googlesource.com/c/go/+/303091
Run-TryBot: Dan Scales <danscales@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Trust: Dan Scales <danscales@google.com>
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>

1 files changed, 601 insertions, 0 deletions

diff --git a/test/typeparam/list2.go b/test/typeparam/list2.go
new file mode 100644
index 0000000000..385193d876
--- /dev/null
+++ b/test/typeparam/list2.go
@@ -0,0 +1,601 @@
+// run -gcflags=-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 list provides a doubly linked list of some element type
+// (generic form of the "container/list" package).
+
+package main
+
+import (
+	"fmt"
+	"strconv"
+)
+
+// Element is an element of a linked list.
+type _Element[T any] struct {
+	// Next and previous pointers in the doubly-linked list of elements.
+	// To simplify the implementation, internally a list l is implemented
+	// as a ring, such that &l.root is both the next element of the last
+	// list element (l.Back()) and the previous element of the first list
+	// element (l.Front()).
+	next, prev *_Element[T]
+
+	// The list to which this element belongs.
+	list *_List[T]
+
+	// The value stored with this element.
+	Value T
+}
+
+// Next returns the next list element or nil.
+func (e *_Element[T]) Next() *_Element[T] {
+	if p := e.next; e.list != nil && p != &e.list.root {
+		return p
+	}
+	return nil
+}
+
+// Prev returns the previous list element or nil.
+func (e *_Element[T]) Prev() *_Element[T] {
+	if p := e.prev; e.list != nil && p != &e.list.root {
+		return p
+	}
+	return nil
+}
+
+// _List represents a doubly linked list.
+// The zero value for _List is an empty list ready to use.
+type _List[T any] struct {
+	root _Element[T] // sentinel list element, only &root, root.prev, and root.next are used
+	len  int     // current list length excluding (this) sentinel element
+}
+
+// Init initializes or clears list l.
+func (l *_List[T]) Init() *_List[T] {
+	l.root.next = &l.root
+	l.root.prev = &l.root
+	l.len = 0
+	return l
+}
+
+// New returns an initialized list.
+func _New[T any]() *_List[T] { return new(_List[T]).Init() }
+
+// Len returns the number of elements of list l.
+// The complexity is O(1).
+func (l *_List[_]) Len() int { return l.len }
+
+// Front returns the first element of list l or nil if the list is empty.
+func (l *_List[T]) Front() *_Element[T] {
+	if l.len == 0 {
+		return nil
+	}
+	return l.root.next
+}
+
+// Back returns the last element of list l or nil if the list is empty.
+func (l *_List[T]) Back() *_Element[T] {
+	if l.len == 0 {
+		return nil
+	}
+	return l.root.prev
+}
+
+// lazyInit lazily initializes a zero _List value.
+func (l *_List[_]) lazyInit() {
+	if l.root.next == nil {
+		l.Init()
+	}
+}
+
+// insert inserts e after at, increments l.len, and returns e.
+func (l *_List[T]) insert(e, at *_Element[T]) *_Element[T] {
+	e.prev = at
+	e.next = at.next
+	e.prev.next = e
+	e.next.prev = e
+	e.list = l
+	l.len++
+	return e
+}
+
+// insertValue is a convenience wrapper for insert(&_Element[T]{Value: v}, at).
+func (l *_List[T]) insertValue(v T, at *_Element[T]) *_Element[T] {
+	return l.insert(&_Element[T]{Value: v}, at)
+}
+
+// remove removes e from its list, decrements l.len, and returns e.
+func (l *_List[T]) remove(e *_Element[T]) *_Element[T] {
+	e.prev.next = e.next
+	e.next.prev = e.prev
+	e.next = nil // avoid memory leaks
+	e.prev = nil // avoid memory leaks
+	e.list = nil
+	l.len--
+	return e
+}
+
+// move moves e to next to at and returns e.
+func (l *_List[T]) move(e, at *_Element[T]) *_Element[T] {
+	if e == at {
+		return e
+	}
+	e.prev.next = e.next
+	e.next.prev = e.prev
+
+	e.prev = at
+	e.next = at.next
+	e.prev.next = e
+	e.next.prev = e
+
+	return e
+}
+
+// Remove removes e from l if e is an element of list l.
+// It returns the element value e.Value.
+// The element must not be nil.
+func (l *_List[T]) Remove(e *_Element[T]) T {
+	if e.list == l {
+		// if e.list == l, l must have been initialized when e was inserted
+		// in l or l == nil (e is a zero _Element) and l.remove will crash
+		l.remove(e)
+	}
+	return e.Value
+}
+
+// PushFront inserts a new element e with value v at the front of list l and returns e.
+func (l *_List[T]) PushFront(v T) *_Element[T] {
+	l.lazyInit()
+	return l.insertValue(v, &l.root)
+}
+
+// PushBack inserts a new element e with value v at the back of list l and returns e.
+func (l *_List[T]) PushBack(v T) *_Element[T] {
+	l.lazyInit()
+	return l.insertValue(v, l.root.prev)
+}
+
+// InsertBefore inserts a new element e with value v immediately before mark and returns e.
+// If mark is not an element of l, the list is not modified.
+// The mark must not be nil.
+func (l *_List[T]) InsertBefore(v T, mark *_Element[T]) *_Element[T] {
+	if mark.list != l {
+		return nil
+	}
+	// see comment in _List.Remove about initialization of l
+	return l.insertValue(v, mark.prev)
+}
+
+// InsertAfter inserts a new element e with value v immediately after mark and returns e.
+// If mark is not an element of l, the list is not modified.
+// The mark must not be nil.
+func (l *_List[T]) InsertAfter(v T, mark *_Element[T]) *_Element[T] {
+	if mark.list != l {
+		return nil
+	}
+	// see comment in _List.Remove about initialization of l
+	return l.insertValue(v, mark)
+}
+
+// MoveToFront moves element e to the front of list l.
+// If e is not an element of l, the list is not modified.
+// The element must not be nil.
+func (l *_List[T]) MoveToFront(e *_Element[T]) {
+	if e.list != l || l.root.next == e {
+		return
+	}
+	// see comment in _List.Remove about initialization of l
+	l.move(e, &l.root)
+}
+
+// MoveToBack moves element e to the back of list l.
+// If e is not an element of l, the list is not modified.
+// The element must not be nil.
+func (l *_List[T]) MoveToBack(e *_Element[T]) {
+	if e.list != l || l.root.prev == e {
+		return
+	}
+	// see comment in _List.Remove about initialization of l
+	l.move(e, l.root.prev)
+}
+
+// MoveBefore moves element e to its new position before mark.
+// If e or mark is not an element of l, or e == mark, the list is not modified.
+// The element and mark must not be nil.
+func (l *_List[T]) MoveBefore(e, mark *_Element[T]) {
+	if e.list != l || e == mark || mark.list != l {
+		return
+	}
+	l.move(e, mark.prev)
+}
+
+// MoveAfter moves element e to its new position after mark.
+// If e or mark is not an element of l, or e == mark, the list is not modified.
+// The element and mark must not be nil.
+func (l *_List[T]) MoveAfter(e, mark *_Element[T]) {
+	if e.list != l || e == mark || mark.list != l {
+		return
+	}
+	l.move(e, mark)
+}
+
+// PushBackList inserts a copy of an other list at the back of list l.
+// The lists l and other may be the same. They must not be nil.
+func (l *_List[T]) PushBackList(other *_List[T]) {
+	l.lazyInit()
+	for i, e := other.Len(), other.Front(); i > 0; i, e = i-1, e.Next() {
+		l.insertValue(e.Value, l.root.prev)
+	}
+}
+
+// PushFrontList inserts a copy of an other list at the front of list l.
+// The lists l and other may be the same. They must not be nil.
+func (l *_List[T]) PushFrontList(other *_List[T]) {
+	l.lazyInit()
+	for i, e := other.Len(), other.Back(); i > 0; i, e = i-1, e.Prev() {
+		l.insertValue(e.Value, &l.root)
+	}
+}
+
+// Transform runs a transform function on a list returning a new list.
+func _Transform[TElem1, TElem2 any](lst *_List[TElem1], f func(TElem1) TElem2) *_List[TElem2] {
+	ret := _New[TElem2]()
+	for p := lst.Front(); p != nil; p = p.Next() {
+		ret.PushBack(f(p.Value))
+	}
+	return ret
+}
+
+func checkListLen[T any](l *_List[T], len int) bool {
+	if n := l.Len(); n != len {
+		panic(fmt.Sprintf("l.Len() = %d, want %d", n, len))
+		return false
+	}
+	return true
+}
+
+func checkListPointers[T any](l *_List[T], es []*_Element[T]) {
+	root := &l.root
+
+	if !checkListLen(l, len(es)) {
+		return
+	}
+
+	// zero length lists must be the zero value or properly initialized (sentinel circle)
+	if len(es) == 0 {
+		if l.root.next != nil && l.root.next != root || l.root.prev != nil && l.root.prev != root {
+			panic(fmt.Sprintf("l.root.next = %p, l.root.prev = %p; both should both be nil or %p", l.root.next, l.root.prev, root))
+		}
+		return
+	}
+	// len(es) > 0
+
+	// check internal and external prev/next connections
+	for i, e := range es {
+		prev := root
+		Prev := (*_Element[T])(nil)
+		if i > 0 {
+			prev = es[i-1]
+			Prev = prev
+		}
+		if p := e.prev; p != prev {
+			panic(fmt.Sprintf("elt[%d](%p).prev = %p, want %p", i, e, p, prev))
+		}
+		if p := e.Prev(); p != Prev {
+			panic(fmt.Sprintf("elt[%d](%p).Prev() = %p, want %p", i, e, p, Prev))
+		}
+
+		next := root
+		Next := (*_Element[T])(nil)
+		if i < len(es)-1 {
+			next = es[i+1]
+			Next = next
+		}
+		if n := e.next; n != next {
+			panic(fmt.Sprintf("elt[%d](%p).next = %p, want %p", i, e, n, next))
+		}
+		if n := e.Next(); n != Next {
+			panic(fmt.Sprintf("elt[%d](%p).Next() = %p, want %p", i, e, n, Next))
+		}
+	}
+}
+
+func TestList() {
+	l := _New[string]()
+	checkListPointers(l, []*(_Element[string]){})
+
+	// Single element list
+	e := l.PushFront("a")
+	checkListPointers(l, []*(_Element[string]){e})
+	l.MoveToFront(e)
+	checkListPointers(l, []*(_Element[string]){e})
+	l.MoveToBack(e)
+	checkListPointers(l, []*(_Element[string]){e})
+	l.Remove(e)
+	checkListPointers(l, []*(_Element[string]){})
+
+	// Bigger list
+	l2 := _New[int]()
+	e2 := l2.PushFront(2)
+	e1 := l2.PushFront(1)
+	e3 := l2.PushBack(3)
+	e4 := l2.PushBack(600)
+	checkListPointers(l2, []*(_Element[int]){e1, e2, e3, e4})
+
+	l2.Remove(e2)
+	checkListPointers(l2, []*(_Element[int]){e1, e3, e4})
+
+	l2.MoveToFront(e3) // move from middle
+	checkListPointers(l2, []*(_Element[int]){e3, e1, e4})
+
+	l2.MoveToFront(e1)
+	l2.MoveToBack(e3) // move from middle
+	checkListPointers(l2, []*(_Element[int]){e1, e4, e3})
+
+	l2.MoveToFront(e3) // move from back
+	checkListPointers(l2, []*(_Element[int]){e3, e1, e4})
+	l2.MoveToFront(e3) // should be no-op
+	checkListPointers(l2, []*(_Element[int]){e3, e1, e4})
+
+	l2.MoveToBack(e3) // move from front
+	checkListPointers(l2, []*(_Element[int]){e1, e4, e3})
+	l2.MoveToBack(e3) // should be no-op
+	checkListPointers(l2, []*(_Element[int]){e1, e4, e3})
+
+	e2 = l2.InsertBefore(2, e1) // insert before front
+	checkListPointers(l2, []*(_Element[int]){e2, e1, e4, e3})
+	l2.Remove(e2)
+	e2 = l2.InsertBefore(2, e4) // insert before middle
+	checkListPointers(l2, []*(_Element[int]){e1, e2, e4, e3})
+	l2.Remove(e2)
+	e2 = l2.InsertBefore(2, e3) // insert before back
+	checkListPointers(l2, []*(_Element[int]){e1, e4, e2, e3})
+	l2.Remove(e2)
+
+	e2 = l2.InsertAfter(2, e1) // insert after front
+	checkListPointers(l2, []*(_Element[int]){e1, e2, e4, e3})
+	l2.Remove(e2)
+	e2 = l2.InsertAfter(2, e4) // insert after middle
+	checkListPointers(l2, []*(_Element[int]){e1, e4, e2, e3})
+	l2.Remove(e2)
+	e2 = l2.InsertAfter(2, e3) // insert after back
+	checkListPointers(l2, []*(_Element[int]){e1, e4, e3, e2})
+	l2.Remove(e2)
+
+	// Check standard iteration.
+	sum := 0
+	for e := l2.Front(); e != nil; e = e.Next() {
+		sum += e.Value
+	}
+	if sum != 604 {
+		panic(fmt.Sprintf("sum over l = %d, want 604", sum))
+	}
+
+	// Clear all elements by iterating
+	var next *_Element[int]
+	for e := l2.Front(); e != nil; e = next {
+		next = e.Next()
+		l2.Remove(e)
+	}
+	checkListPointers(l2, []*(_Element[int]){})
+}
+
+func checkList[T comparable](l *_List[T], es []interface{}) {
+	if !checkListLen(l, len(es)) {
+		return
+	}
+
+	i := 0
+	for e := l.Front(); e != nil; e = e.Next() {
+		le := e.Value
+		// Comparison between a generically-typed variable le and an interface.
+		if le != es[i] {
+			panic(fmt.Sprintf("elt[%d].Value = %v, want %v", i, le, es[i]))
+		}
+		i++
+	}
+}
+
+func TestExtending() {
+	l1 := _New[int]()
+	l2 := _New[int]()
+
+	l1.PushBack(1)
+	l1.PushBack(2)
+	l1.PushBack(3)
+
+	l2.PushBack(4)
+	l2.PushBack(5)
+
+	l3 := _New[int]()
+	l3.PushBackList(l1)
+	checkList(l3, []interface{}{1, 2, 3})
+	l3.PushBackList(l2)
+	checkList(l3, []interface{}{1, 2, 3, 4, 5})
+
+	l3 = _New[int]()
+	l3.PushFrontList(l2)
+	checkList(l3, []interface{}{4, 5})
+	l3.PushFrontList(l1)
+	checkList(l3, []interface{}{1, 2, 3, 4, 5})
+
+	checkList(l1, []interface{}{1, 2, 3})
+	checkList(l2, []interface{}{4, 5})
+
+	l3 = _New[int]()
+	l3.PushBackList(l1)
+	checkList(l3, []interface{}{1, 2, 3})
+	l3.PushBackList(l3)
+	checkList(l3, []interface{}{1, 2, 3, 1, 2, 3})
+
+	l3 = _New[int]()
+	l3.PushFrontList(l1)
+	checkList(l3, []interface{}{1, 2, 3})
+	l3.PushFrontList(l3)
+	checkList(l3, []interface{}{1, 2, 3, 1, 2, 3})
+
+	l3 = _New[int]()
+	l1.PushBackList(l3)
+	checkList(l1, []interface{}{1, 2, 3})
+	l1.PushFrontList(l3)
+	checkList(l1, []interface{}{1, 2, 3})
+}
+
+func TestRemove() {
+	l := _New[int]()
+	e1 := l.PushBack(1)
+	e2 := l.PushBack(2)
+	checkListPointers(l, []*(_Element[int]){e1, e2})
+	e := l.Front()
+	l.Remove(e)
+	checkListPointers(l, []*(_Element[int]){e2})
+	l.Remove(e)
+	checkListPointers(l, []*(_Element[int]){e2})
+}
+
+func TestIssue4103() {
+	l1 := _New[int]()
+	l1.PushBack(1)
+	l1.PushBack(2)
+
+	l2 := _New[int]()
+	l2.PushBack(3)
+	l2.PushBack(4)
+
+	e := l1.Front()
+	l2.Remove(e) // l2 should not change because e is not an element of l2
+	if n := l2.Len(); n != 2 {
+		panic(fmt.Sprintf("l2.Len() = %d, want 2", n))
+	}
+
+	l1.InsertBefore(8, e)
+	if n := l1.Len(); n != 3 {
+		panic(fmt.Sprintf("l1.Len() = %d, want 3", n))
+	}
+}
+
+func TestIssue6349() {
+	l := _New[int]()
+	l.PushBack(1)
+	l.PushBack(2)
+
+	e := l.Front()
+	l.Remove(e)
+	if e.Value != 1 {
+		panic(fmt.Sprintf("e.value = %d, want 1", e.Value))
+	}
+	if e.Next() != nil {
+		panic(fmt.Sprintf("e.Next() != nil"))
+	}
+	if e.Prev() != nil {
+		panic(fmt.Sprintf("e.Prev() != nil"))
+	}
+}
+
+func TestMove() {
+	l := _New[int]()
+	e1 := l.PushBack(1)
+	e2 := l.PushBack(2)
+	e3 := l.PushBack(3)
+	e4 := l.PushBack(4)
+
+	l.MoveAfter(e3, e3)
+	checkListPointers(l, []*(_Element[int]){e1, e2, e3, e4})
+	l.MoveBefore(e2, e2)
+	checkListPointers(l, []*(_Element[int]){e1, e2, e3, e4})
+
+	l.MoveAfter(e3, e2)
+	checkListPointers(l, []*(_Element[int]){e1, e2, e3, e4})
+	l.MoveBefore(e2, e3)
+	checkListPointers(l, []*(_Element[int]){e1, e2, e3, e4})
+
+	l.MoveBefore(e2, e4)
+	checkListPointers(l, []*(_Element[int]){e1, e3, e2, e4})
+	e2, e3 = e3, e2
+
+	l.MoveBefore(e4, e1)
+	checkListPointers(l, []*(_Element[int]){e4, e1, e2, e3})
+	e1, e2, e3, e4 = e4, e1, e2, e3
+
+	l.MoveAfter(e4, e1)
+	checkListPointers(l, []*(_Element[int]){e1, e4, e2, e3})
+	e2, e3, e4 = e4, e2, e3
+
+	l.MoveAfter(e2, e3)
+	checkListPointers(l, []*(_Element[int]){e1, e3, e2, e4})
+	e2, e3 = e3, e2
+}
+
+// Test PushFront, PushBack, PushFrontList, PushBackList with uninitialized _List
+func TestZeroList() {
+	var l1 = new(_List[int])
+	l1.PushFront(1)
+	checkList(l1, []interface{}{1})
+
+	var l2 = new(_List[int])
+	l2.PushBack(1)
+	checkList(l2, []interface{}{1})
+
+	var l3 = new(_List[int])
+	l3.PushFrontList(l1)
+	checkList(l3, []interface{}{1})
+
+	var l4 = new(_List[int])
+	l4.PushBackList(l2)
+	checkList(l4, []interface{}{1})
+}
+
+// Test that a list l is not modified when calling InsertBefore with a mark that is not an element of l.
+func TestInsertBeforeUnknownMark() {
+	var l _List[int]
+	l.PushBack(1)
+	l.PushBack(2)
+	l.PushBack(3)
+	l.InsertBefore(1, new(_Element[int]))
+	checkList(&l, []interface{}{1, 2, 3})
+}
+
+// Test that a list l is not modified when calling InsertAfter with a mark that is not an element of l.
+func TestInsertAfterUnknownMark() {
+	var l _List[int]
+	l.PushBack(1)
+	l.PushBack(2)
+	l.PushBack(3)
+	l.InsertAfter(1, new(_Element[int]))
+	checkList(&l, []interface{}{1, 2, 3})
+}
+
+// Test that a list l is not modified when calling MoveAfter or MoveBefore with a mark that is not an element of l.
+func TestMoveUnknownMark() {
+	var l1 _List[int]
+	e1 := l1.PushBack(1)
+
+	var l2 _List[int]
+	e2 := l2.PushBack(2)
+
+	l1.MoveAfter(e1, e2)
+	checkList(&l1, []interface{}{1})
+	checkList(&l2, []interface{}{2})
+
+	l1.MoveBefore(e1, e2)
+	checkList(&l1, []interface{}{1})
+	checkList(&l2, []interface{}{2})
+}
+
+// Test the Transform function.
+func TestTransform() {
+	l1 := _New[int]()
+	l1.PushBack(1)
+	l1.PushBack(2)
+	l2 := _Transform(l1, strconv.Itoa)
+	checkList(l2, []interface{}{"1", "2"})
+}
+
+
+func main() {
+	TestList()
+}
+