diff --git a/source/diet/defs.d b/source/diet/defs.d
index 81dee80..d69ff87 100644
--- a/source/diet/defs.d
+++ b/source/diet/defs.d
@@ -27,7 +27,7 @@ alias DietParserException = Exception;
 		Throws a `DietParserException` when called with a `false` condition at
 		run time.
 */
-void enforcep(bool cond, lazy string text, Location loc) @safe
+void enforcep(bool cond, lazy string text, ref const Location loc) @safe
 {
 	if (__ctfe) {
 		import std.conv : to;
diff --git a/source/diet/dom.d b/source/diet/dom.d
index e0be8eb..4dcb3ee 100644
--- a/source/diet/dom.d
+++ b/source/diet/dom.d
@@ -125,6 +125,9 @@ NodeContent[] toNodeContent(in AttributeContent[] contents, Location loc)
 	/// Original text used to look up the translation (only set if translated)
 	string translationKey;
 
+
+scope:
+
 	/// Constructs a new node.
 	this(Location loc = Location.init, string name = null,
 		Attribute[] attributes = null, NodeContent[] contents = null,
@@ -163,7 +166,7 @@ NodeContent[] toNodeContent(in AttributeContent[] contents, Location loc)
 			text = The text to append to the node
 			loc = Location in the source file
 	*/
-	void addText(string text, in Location loc)
+	void addText(string text, ref const Location loc)
 	{
 		if (contents.length && contents[$-1].kind == NodeContent.Kind.text && contents[$-1].loc == loc)
 			contents[$-1].value ~= text;
@@ -179,7 +182,7 @@ NodeContent[] toNodeContent(in AttributeContent[] contents, Location loc)
 
 	/** Determines if this node has any non-whitespace contents. */
 	bool hasNonWhitespaceContent()
-	const {
+	const scope {
 		import std.algorithm.searching : any;
 		return contents.any!(c => c.kind != NodeContent.Kind.text || c.value.ctstrip.length > 0);
 	}
diff --git a/source/diet/html.d b/source/diet/html.d
index e1679e0..f4b1f41 100644
--- a/source/diet/html.d
+++ b/source/diet/html.d
@@ -738,7 +738,7 @@ private string getDoctypeMixin(ref CTX ctx, in Node node) @safe
 	return ctx.rawText(node.loc, "<"~doctype_str~">");
 }
 
-private string getCodeMixin(ref CTX ctx, const ref Node node, bool in_pre) @safe
+private string getCodeMixin(ref CTX ctx, in Node node, bool in_pre) @safe
 {
 	enforcep(node.attributes.length == 0, "Code lines may not have attributes.", node.loc);
 	enforcep(node.attribs == NodeAttribs.none, "Code lines may not specify translation or text block suffixes.", node.loc);
@@ -762,7 +762,7 @@ private string getCodeMixin(ref CTX ctx, const ref Node node, bool in_pre) @safe
 	return ret;
 }
 
-private string getCommentMixin(ref CTX ctx, const ref Node node) @safe
+private string getCommentMixin(ref CTX ctx, in Node node) @safe
 {
 	string ret = ctx.rawText(node.loc, "<!--");
 	ctx.depth++;
diff --git a/source/diet/internal/string.d b/source/diet/internal/string.d
index 579edd3..ee8780f 100644
--- a/source/diet/internal/string.d
+++ b/source/diet/internal/string.d
@@ -45,7 +45,7 @@ string dstringEscape(in string str)
 	return ret;
 }
 
-string dstringUnescape(in string str)
+string dstringUnescape(in return string str)
 {
 	string ret;
 	size_t i, start = 0;
diff --git a/source/diet/parser.d b/source/diet/parser.d
index 92f44cc..4bdfe2a 100644
--- a/source/diet/parser.d
+++ b/source/diet/parser.d
@@ -675,8 +675,8 @@ Document parseDiet(alias TR = identity)(const(InputFile)[] files)
 string identity(string str, string context = null) nothrow @safe @nogc { return str; }
 
 
-private string parseIdent(in string str, ref size_t start,
-	   	string breakChars, in Location loc)
+private string parseIdent(return in string str, ref size_t start,
+	   	string breakChars, ref const Location loc)
 @safe {
 	import std.array : back;
 	/* The stack is used to keep track of opening and
@@ -1347,7 +1347,7 @@ private string skipLine(ref string input, ref Location loc)
 	return ret;
 }
 
-private void parseAttributes(ref string input, ref size_t i, ref Node node, in Location loc)
+private void parseAttributes(ref string input, ref size_t i, ref Node node, ref const Location loc)
 @safe {
 	assert(i < input.length && input[i] == '(');
 	i++;
@@ -1391,7 +1391,7 @@ private void parseAttributes(ref string input, ref size_t i, ref Node node, in L
 	i++;
 }
 
-private void parseAttributeText(string input, ref AttributeContent[] dst, in Location loc)
+private void parseAttributeText(string input, ref AttributeContent[] dst, ref const Location loc)
 @safe {
 	size_t sidx = 0, idx = 0;
 
@@ -1428,7 +1428,7 @@ private void parseAttributeText(string input, ref AttributeContent[] dst, in Loc
 	input = input[idx .. $];
 }
 
-private string skipUntilClosingBrace(in string s, ref size_t idx, in Location loc)
+private string skipUntilClosingBrace(return in string s, ref size_t idx, ref const Location loc)
 @safe {
 	import std.algorithm.comparison : among;
 
@@ -1445,7 +1445,7 @@ private string skipUntilClosingBrace(in string s, ref size_t idx, in Location lo
 	assert(false);
 }
 
-private string skipUntilClosingBracket(in string s, ref size_t idx, in Location loc)
+private string skipUntilClosingBracket(return in string s, ref size_t idx, ref const Location loc)
 @safe {
 	import std.algorithm.comparison : among;
 
@@ -1502,7 +1502,7 @@ private string skipIndent(ref string input)
 
 private bool isIndentChar(dchar ch) @safe { return ch == ' ' || ch == '\t'; }
 
-private string skipAnyWhitespace(in string s, ref size_t idx)
+private string skipAnyWhitespace(return in string s, ref size_t idx)
 @safe {
 	import std.ascii : isWhite;
 
@@ -1570,7 +1570,7 @@ private bool isStringLiteral(string str)
 	assert(!isStringLiteral(`"name" value="#{name}"`));
 }
 
-private string skipExpression(in string s, ref size_t idx, in Location loc, bool multiline = false)
+private string skipExpression(return in string s, ref size_t idx, ref const Location loc, bool multiline = false)
 @safe {
 	string clamp_stack;
 	size_t start = idx;
@@ -1608,7 +1608,7 @@ private string skipExpression(in string s, ref size_t idx, in Location loc, bool
 }
 
 
-private string skipAttribString(in string s, ref size_t idx, char delimiter, in Location loc)
+private string skipAttribString(return in string s, ref size_t idx, char delimiter, ref const Location loc)
 @safe {
 	size_t start = idx;
 	while( idx < s.length ){
diff --git a/test.sh b/test.sh
index b244701..e6d5404 100755
--- a/test.sh
+++ b/test.sh
@@ -12,6 +12,8 @@ echo "Checing makepot for successful compilation..."
 dub build :makepot
 
 if [ "$DC" == "ldc2" ]; then
-	echo "Testing for DIP 1000 compatibility..."
-	DFLAGS="--preview=dip1000 --preview=dip25" dub build 
+	echo "Testing for DIP 1000/1021/in compatibility..."
+	DFLAGS="-preview=dip1000 -preview=dip1021" dub build
+	DFLAGS="-preview=in" dub build
+	DFLAGS="-preview=dip1000 -preview=dip1021 -preview=in" dub build
 fi