[dev.typeparams] all: merge master (798ec73) into dev.typeparams

Merge List:

+ 2021-07-22 798ec73519 runtime: don't clear timerModifiedEarliest if adjustTimers is 0
+ 2021-07-22 fdb45acd1f runtime: move mem profile sampling into m-acquired section
+ 2021-07-21 3e48c0381f reflect: add missing copyright header
+ 2021-07-21 48c88f1b1b reflect: add Value.CanConvert
+ 2021-07-20 9e26569293 cmd/go: don't add C compiler ID to hash for standard library
+ 2021-07-20 d568e6e075 runtime/debug: skip TestPanicOnFault on netbsd/arm

Change-Id: I87e1cd4614bb3b00807f18dfdd02664dcaecaebd

1 files changed, 20 insertions, 0 deletions

diff --git a/src/reflect/value.go b/src/reflect/value.go
index 7589966e22..b4b2d2e38b 100644
--- a/src/reflect/value.go
+++ b/src/reflect/value.go
@@ -2807,6 +2807,26 @@ func (v Value) Convert(t Type) Value {
 	return op(v, t)
 }
 
+// CanConvert reports whether the value v can be converted to type t.
+// If v.CanConvert(t) returns true then v.Convert(t) will not panic.
+func (v Value) CanConvert(t Type) bool {
+	vt := v.Type()
+	if !vt.ConvertibleTo(t) {
+		return false
+	}
+	// Currently the only conversion that is OK in terms of type
+	// but that can panic depending on the value is converting
+	// from slice to pointer-to-array.
+	if vt.Kind() == Slice && t.Kind() == Ptr && t.Elem().Kind() == Array {
+		n := t.Elem().Len()
+		h := (*unsafeheader.Slice)(v.ptr)
+		if n > h.Len {
+			return false
+		}
+	}
+	return true
+}
+
 // convertOp returns the function to convert a value of type src
 // to a value of type dst. If the conversion is illegal, convertOp returns nil.
 func convertOp(dst, src *rtype) func(Value, Type) Value {