From 2ac53fa1642f022e4f4277913c93e191b0d15abb Mon Sep 17 00:00:00 2001
From: dkorpel <dkorpel@gmail.com>
Date: Fri, 24 Dec 2021 11:55:02 +0100
Subject: [PATCH] Make `toLower` and `toUpper` `return scope`

---
 std/uni/package.d | 44 ++++++++++++++++++++++++++------------------
 1 file changed, 26 insertions(+), 18 deletions(-)

diff --git a/std/uni/package.d b/std/uni/package.d
index eeeda7218..98735ac1a 100644
--- a/std/uni/package.d
+++ b/std/uni/package.d
@@ -9834,25 +9834,29 @@ dchar toLower(dchar c)
     Returns:
         An array with the same element type as `s`.
 +/
-ElementEncodingType!S[] toLower(S)(S s)
-if (isSomeString!S || (isRandomAccessRange!S && hasLength!S && hasSlicing!S && isSomeChar!(ElementType!S)))
+ElementEncodingType!S[] toLower(S)(return scope S s) @trusted
+if (isSomeString!S)
 {
     static import std.ascii;
+    return toCase!(LowerTriple, std.ascii.toLower)(s);
+}
 
-    static if (isSomeString!S)
-        return () @trusted { return toCase!(LowerTriple, std.ascii.toLower)(s); } ();
-    else
-        return toCase!(LowerTriple, std.ascii.toLower)(s);
+/// ditto
+ElementEncodingType!S[] toLower(S)(S s)
+if (!isSomeString!S && (isRandomAccessRange!S && hasLength!S && hasSlicing!S && isSomeChar!(ElementType!S)))
+{
+    static import std.ascii;
+    return toCase!(LowerTriple, std.ascii.toLower)(s);
 }
 
 // overloads for the most common cases to reduce compile time
 @safe pure /*TODO nothrow*/
 {
-    string toLower(string s)
+    string toLower(return scope string s)
     { return toLower!string(s); }
-    wstring toLower(wstring s)
+    wstring toLower(return scope wstring s)
     { return toLower!wstring(s); }
-    dstring toLower(dstring s)
+    dstring toLower(return scope dstring s)
     { return toLower!dstring(s); }
 
     @safe unittest
@@ -10038,25 +10042,29 @@ dchar toUpper(dchar c)
     Returns:
         An new array with the same element type as `s`.
 +/
-ElementEncodingType!S[] toUpper(S)(S s)
-if (isSomeString!S || (isRandomAccessRange!S && hasLength!S && hasSlicing!S && isSomeChar!(ElementType!S)))
+ElementEncodingType!S[] toUpper(S)(return scope S s) @trusted
+if (isSomeString!S)
 {
     static import std.ascii;
+    return toCase!(UpperTriple, std.ascii.toUpper)(s);
+}
 
-    static if (isSomeString!S)
-        return () @trusted { return toCase!(UpperTriple, std.ascii.toUpper)(s); } ();
-    else
-        return toCase!(UpperTriple, std.ascii.toUpper)(s);
+/// ditto
+ElementEncodingType!S[] toUpper(S)(S s)
+if (!isSomeString!S && (isRandomAccessRange!S && hasLength!S && hasSlicing!S && isSomeChar!(ElementType!S)))
+{
+    static import std.ascii;
+    return toCase!(UpperTriple, std.ascii.toUpper)(s);
 }
 
 // overloads for the most common cases to reduce compile time
 @safe pure /*TODO nothrow*/
 {
-    string toUpper(string s)
+    string toUpper(return scope string s)
     { return toUpper!string(s); }
-    wstring toUpper(wstring s)
+    wstring toUpper(return scope wstring s)
     { return toUpper!wstring(s); }
-    dstring toUpper(dstring s)
+    dstring toUpper(return scope dstring s)
     { return toUpper!dstring(s); }
 
     @safe unittest