[dev.cmdgo] all: merge master (5e6a7e9) into dev.cmdgo

Merge List:

+ 2021-08-26 5e6a7e9b86 embed: remove reference to global variables in docs
+ 2021-08-26 166b691b65 cmd/compile/internal/types2: remove need for instance (struct)
+ 2021-08-26 d6bdae33e9 cmd/compile/internal/types2: address some TODOs (cleanup)
+ 2021-08-26 770df2e18d crypto/tls: fix typo in PreferServerCipherSuites comment
+ 2021-08-26 a6ff433d6a cmd/go: pass -gcflags after other flags generated by the go command
+ 2021-08-25 4f2620285d cmd/compile/internal/types2: fix type set printing and add test
+ 2021-08-25 0ac64f6d70 cmd/compile/internal/types2: rename IsMethodSet to IsConstraint (cleanup)
+ 2021-08-25 4068fb6c21 cmd/compile: always accept 1.18 syntax but complain if not 1.18
+ 2021-08-25 bf0bc4122f go/types, types2: don't re-evaluate context string for each function argument (optimization)
+ 2021-08-25 4158e88f64 cmd/compile/internal/syntax: fix position of type parameter field
+ 2021-08-25 647bef6c59 go/types: implement NewTypeList and use it instead of composite literals
+ 2021-08-25 6cf1d5d0fa cmd/compile: generic SSA rules for simplifying 2 and 3 operand integer arithmetic expressions
+ 2021-08-25 5baf60d472 bytes, strings: optimize Trim for single byte cutsets
+ 2021-08-25 3d667671ad cmd/compile: fix function contains no TParam in generic function
+ 2021-08-25 4f2ebfe34b cmd/compile: allow embed into any byte slice type
+ 2021-08-25 d2f002cb39 time/format: avoid growslice in time.String()/time.GoString()
+ 2021-08-25 08d4cc20ca cmd/compile: fix stencil call expression.
+ 2021-08-25 099b819085 cmd/compile: fix CheckSize() calculation for -G=3 and stencils
+ 2021-08-25 e1fcf8857e test: add test that caused gofrontend compiler crash
+ 2021-08-25 d37b8dedf7 test: add test case that gofrontend miscompiled
+ 2021-08-25 41b99dab0f os/user: don't skip TestLookupGroup if supported
+ 2021-08-25 de1c934b97 cmd/compile: fix checkptr false positive for (*[Big]T)(ptr)[:n:n] pattern
+ 2021-08-24 54cdef1f10 reflect: add MapIter.SetKey and MapIter.SetValue
+ 2021-08-24 5d863f89fe cmd/compile: simplify bad conversion check

Change-Id: I29ab927f0e47f44d82f9307c642900f75f4f678f

2 files changed, 99 insertions, 4 deletions

diff --git a/src/reflect/all_test.go b/src/reflect/all_test.go
index df79f05807..40ac6a95fa 100644
--- a/src/reflect/all_test.go
+++ b/src/reflect/all_test.go
@@ -336,6 +336,47 @@ func TestSetValue(t *testing.T) {
 	}
 }
 
+func TestMapIterSet(t *testing.T) {
+	m := make(map[string]interface{}, len(valueTests))
+	for _, tt := range valueTests {
+		m[tt.s] = tt.i
+	}
+	v := ValueOf(m)
+
+	k := New(v.Type().Key()).Elem()
+	e := New(v.Type().Elem()).Elem()
+
+	iter := v.MapRange()
+	for iter.Next() {
+		iter.SetKey(k)
+		iter.SetValue(e)
+		want := m[k.String()]
+		got := e.Interface()
+		if got != want {
+			t.Errorf("%q: want (%T) %v, got (%T) %v", k.String(), want, want, got, got)
+		}
+		if setkey, key := valueToString(k), valueToString(iter.Key()); setkey != key {
+			t.Errorf("MapIter.Key() = %q, MapIter.SetKey() = %q", key, setkey)
+		}
+		if setval, val := valueToString(e), valueToString(iter.Value()); setval != val {
+			t.Errorf("MapIter.Value() = %q, MapIter.SetValue() = %q", val, setval)
+		}
+	}
+
+	got := int(testing.AllocsPerRun(10, func() {
+		iter := v.MapRange()
+		for iter.Next() {
+			iter.SetKey(k)
+			iter.SetValue(e)
+		}
+	}))
+	// Making a *MapIter and making an hiter both allocate.
+	// Those should be the only two allocations.
+	if got != 2 {
+		t.Errorf("wanted 2 allocs, got %d", got)
+	}
+}
+
 func TestCanSetField(t *testing.T) {
 	type embed struct{ x, X int }
 	type Embed struct{ x, X int }
diff --git a/src/reflect/value.go b/src/reflect/value.go
index de01f13825..a8274cc871 100644
--- a/src/reflect/value.go
+++ b/src/reflect/value.go
@@ -1578,13 +1578,40 @@ func (it *MapIter) Key() Value {
 	if it.it == nil {
 		panic("MapIter.Key called before Next")
 	}
-	if mapiterkey(it.it) == nil {
+	iterkey := mapiterkey(it.it)
+	if iterkey == nil {
 		panic("MapIter.Key called on exhausted iterator")
 	}
 
 	t := (*mapType)(unsafe.Pointer(it.m.typ))
 	ktype := t.key
-	return copyVal(ktype, it.m.flag.ro()|flag(ktype.Kind()), mapiterkey(it.it))
+	return copyVal(ktype, it.m.flag.ro()|flag(ktype.Kind()), iterkey)
+}
+
+// SetKey assigns dst to the key of the iterator's current map entry.
+// It is equivalent to dst.Set(it.Key()), but it avoids allocating a new Value.
+// As in Go, the key must be assignable to dst's type.
+func (it *MapIter) SetKey(dst Value) {
+	if it.it == nil {
+		panic("MapIter.SetKey called before Next")
+	}
+	iterkey := mapiterkey(it.it)
+	if iterkey == nil {
+		panic("MapIter.SetKey called on exhausted iterator")
+	}
+
+	dst.mustBeAssignable()
+	var target unsafe.Pointer
+	if dst.kind() == Interface {
+		target = dst.ptr
+	}
+
+	t := (*mapType)(unsafe.Pointer(it.m.typ))
+	ktype := t.key
+
+	key := Value{ktype, iterkey, it.m.flag | flag(ktype.Kind())}
+	key = key.assignTo("reflect.MapIter.SetKey", dst.typ, target)
+	typedmemmove(dst.typ, dst.ptr, key.ptr)
 }
 
 // Value returns the value of the iterator's current map entry.
@@ -1592,13 +1619,40 @@ func (it *MapIter) Value() Value {
 	if it.it == nil {
 		panic("MapIter.Value called before Next")
 	}
-	if mapiterkey(it.it) == nil {
+	iterelem := mapiterelem(it.it)
+	if iterelem == nil {
 		panic("MapIter.Value called on exhausted iterator")
 	}
 
 	t := (*mapType)(unsafe.Pointer(it.m.typ))
 	vtype := t.elem
-	return copyVal(vtype, it.m.flag.ro()|flag(vtype.Kind()), mapiterelem(it.it))
+	return copyVal(vtype, it.m.flag.ro()|flag(vtype.Kind()), iterelem)
+}
+
+// SetValue assigns dst to the value of the iterator's current map entry.
+// It is equivalent to dst.Set(it.Value()), but it avoids allocating a new Value.
+// As in Go, the value must be assignable to dst's type.
+func (it *MapIter) SetValue(dst Value) {
+	if it.it == nil {
+		panic("MapIter.SetValue called before Next")
+	}
+	iterelem := mapiterelem(it.it)
+	if iterelem == nil {
+		panic("MapIter.SetValue called on exhausted iterator")
+	}
+
+	dst.mustBeAssignable()
+	var target unsafe.Pointer
+	if dst.kind() == Interface {
+		target = dst.ptr
+	}
+
+	t := (*mapType)(unsafe.Pointer(it.m.typ))
+	vtype := t.elem
+
+	elem := Value{vtype, iterelem, it.m.flag | flag(vtype.Kind())}
+	elem = elem.assignTo("reflect.MapIter.SetValue", dst.typ, target)
+	typedmemmove(dst.typ, dst.ptr, elem.ptr)
 }
 
 // Next advances the map iterator and reports whether there is another