diff --git a/src/context/common.ml b/src/context/common.ml
index dd9e4b58ad9..418f70efb32 100644
--- a/src/context/common.ml
+++ b/src/context/common.ml
@@ -1317,3 +1317,100 @@ let get_entry_point com =
 		let e = Option.get com.main in (* must be present at this point *)
 		(snd path, c, e)
 	) com.main_class
+
+let format_string com s p process_expr =
+	let e = ref None in
+	let pmin = ref p.pmin in
+	let min = ref (p.pmin + 1) in
+	let add_expr (enext,p) len =
+		min := !min + len;
+		let enext = process_expr enext p in
+		match !e with
+		| None -> e := Some enext
+		| Some prev ->
+			e := Some (EBinop (OpAdd,prev,enext),punion (pos prev) p)
+	in
+	let add enext len =
+		let p = { p with pmin = !min; pmax = !min + len } in
+		add_expr (enext,p) len
+	in
+	let add_sub start pos =
+		let len = pos - start in
+		if len > 0 || !e = None then add (EConst (String (String.sub s start len,SDoubleQuotes))) len
+	in
+	let len = String.length s in
+	let rec parse start pos =
+		if pos = len then add_sub start pos else
+		let c = String.unsafe_get s pos in
+		let pos = pos + 1 in
+		if c = '\'' then begin
+			incr pmin;
+			incr min;
+		end;
+		if c <> '$' || pos = len then parse start pos else
+		match String.unsafe_get s pos with
+		| '$' ->
+			(* double $ *)
+			add_sub start pos;
+			parse (pos + 1) (pos + 1)
+		| '{' ->
+			parse_group start pos '{' '}' "brace"
+		| 'a'..'z' | 'A'..'Z' | '_' ->
+			add_sub start (pos - 1);
+			incr min;
+			let rec loop i =
+				if i = len then i else
+				let c = String.unsafe_get s i in
+				match c with
+				| 'a'..'z' | 'A'..'Z' | '0'..'9' | '_' -> loop (i+1)
+				| _ -> i
+			in
+			let iend = loop (pos + 1) in
+			let len = iend - pos in
+			add (EConst (Ident (String.sub s pos len))) len;
+			parse (pos + len) (pos + len)
+		| _ ->
+			(* keep as-it *)
+			parse start pos
+	and parse_group start pos gopen gclose gname =
+		add_sub start (pos - 1);
+		let rec loop groups i =
+			if i = len then
+				match groups with
+				| [] -> die "" __LOC__
+				| g :: _ -> Error.raise_typing_error ("Unclosed " ^ gname) { p with pmin = !pmin + g + 1; pmax = !pmin + g + 2 }
+			else
+				let c = String.unsafe_get s i in
+				if c = gopen then
+					loop (i :: groups) (i + 1)
+				else if c = gclose then begin
+					let groups = List.tl groups in
+					if groups = [] then i else loop groups (i + 1)
+				end else
+					loop groups (i + 1)
+		in
+		let send = loop [pos] (pos + 1) in
+		let slen = send - pos - 1 in
+		let scode = String.sub s (pos + 1) slen in
+		min := !min + 2;
+		begin
+			let e =
+				let ep = { p with pmin = !pmin + pos + 2; pmax = !pmin + send + 1 } in
+				let error msg pos =
+					if Lexer.string_is_whitespace scode then Error.raise_typing_error "Expression cannot be empty" ep
+					else Error.raise_typing_error msg pos
+				in
+				match ParserEntry.parse_expr_string com.defines scode ep error true with
+					| ParseSuccess(data,_,_) -> data
+					| ParseError(_,(msg,p),_) -> error (Parser.error_msg msg) p
+			in
+			add_expr e slen
+		end;
+		min := !min + 1;
+		parse (send + 1) (send + 1)
+	in
+	parse 0 0;
+	match !e with
+	| None -> die "" __LOC__
+	| Some e -> e
+
diff --git a/src/typing/macroContext.ml b/src/typing/macroContext.ml
index 64131ae766b..04776624bba 100644
--- a/src/typing/macroContext.ml
+++ b/src/typing/macroContext.ml
@@ -262,7 +262,7 @@ let make_macro_com_api com p =
 			!macro_enable_cache
 		);
 		format_string = (fun s p ->
-			Interp.exc_string "unsupported"
+			Common.format_string com s p (fun e p -> (e,p))
 		);
 		cast_or_unify = (fun t e p ->
 			Interp.exc_string "unsupported"
@@ -525,9 +525,6 @@ and promote_com_api com_api ctx p =
 		MacroApi.current_module = (fun() ->
 			ctx.m.curmod
 		);
-		MacroApi.format_string = (fun s p ->
-			ctx.g.do_format_string ctx s p
-		);
 		MacroApi.cast_or_unify = (fun t e p ->
 			typing_timer ctx true (fun () ->
 				try
diff --git a/src/typing/typer.ml b/src/typing/typer.ml
index bac11e40cf6..0a71bbb9b20 100644
--- a/src/typing/typer.ml
+++ b/src/typing/typer.ml
@@ -729,104 +729,12 @@ and type_vars ctx vl p =
 		mk (TMeta((Meta.MergeBlock,[],p), e)) e.etype e.epos
 
 and format_string ctx s p =
-	let e = ref None in
-	let pmin = ref p.pmin in
-	let min = ref (p.pmin + 1) in
-	let add_expr (enext,p) len =
-		min := !min + len;
-		let enext = if ctx.in_display && DisplayPosition.display_position#enclosed_in p then
+	Common.format_string ctx.com s p (fun enext p ->
+		if ctx.in_display && DisplayPosition.display_position#enclosed_in p then
 			Display.ExprPreprocessing.process_expr ctx.com (enext,p)
 		else
 			enext,p
-		in
-		match !e with
-		| None -> e := Some enext
-		| Some prev ->
-			e := Some (EBinop (OpAdd,prev,enext),punion (pos prev) p)
-	in
-	let add enext len =
-		let p = { p with pmin = !min; pmax = !min + len } in
-		add_expr (enext,p) len
-	in
-	let add_sub start pos =
-		let len = pos - start in
-		if len > 0 || !e = None then add (EConst (String (String.sub s start len,SDoubleQuotes))) len
-	in
-	let len = String.length s in
-	let rec parse start pos =
-		if pos = len then add_sub start pos else
-		let c = String.unsafe_get s pos in
-		let pos = pos + 1 in
-		if c = '\'' then begin
-			incr pmin;
-			incr min;
-		end;
-		if c <> '$' || pos = len then parse start pos else
-		match String.unsafe_get s pos with
-		| '$' ->
-			(* double $ *)
-			add_sub start pos;
-			parse (pos + 1) (pos + 1)
-		| '{' ->
-			parse_group start pos '{' '}' "brace"
-		| 'a'..'z' | 'A'..'Z' | '_' ->
-			add_sub start (pos - 1);
-			incr min;
-			let rec loop i =
-				if i = len then i else
-				let c = String.unsafe_get s i in
-				match c with
-				| 'a'..'z' | 'A'..'Z' | '0'..'9' | '_' -> loop (i+1)
-				| _ -> i
-			in
-			let iend = loop (pos + 1) in
-			let len = iend - pos in
-			add (EConst (Ident (String.sub s pos len))) len;
-			parse (pos + len) (pos + len)
-		| _ ->
-			(* keep as-it *)
-			parse start pos
-	and parse_group start pos gopen gclose gname =
-		add_sub start (pos - 1);
-		let rec loop groups i =
-			if i = len then
-				match groups with
-				| [] -> die "" __LOC__
-				| g :: _ -> raise_typing_error ("Unclosed " ^ gname) { p with pmin = !pmin + g + 1; pmax = !pmin + g + 2 }
-			else
-				let c = String.unsafe_get s i in
-				if c = gopen then
-					loop (i :: groups) (i + 1)
-				else if c = gclose then begin
-					let groups = List.tl groups in
-					if groups = [] then i else loop groups (i + 1)
-				end else
-					loop groups (i + 1)
-		in
-		let send = loop [pos] (pos + 1) in
-		let slen = send - pos - 1 in
-		let scode = String.sub s (pos + 1) slen in
-		min := !min + 2;
-		begin
-			let e =
-				let ep = { p with pmin = !pmin + pos + 2; pmax = !pmin + send + 1 } in
-				let error msg pos =
-					if Lexer.string_is_whitespace scode then raise_typing_error "Expression cannot be empty" ep
-					else raise_typing_error msg pos
-				in
-				match ParserEntry.parse_expr_string ctx.com.defines scode ep error true with
-					| ParseSuccess(data,_,_) -> data
-					| ParseError(_,(msg,p),_) -> error (Parser.error_msg msg) p
-			in
-			add_expr e slen
-		end;
-		min := !min + 1;
-		parse (send + 1) (send + 1)
-	in
-	parse 0 0;
-	match !e with
-	| None -> die "" __LOC__
-	| Some e -> e
+	)
 
 and type_block ctx el with_type p =
 	let merge acc e = match e.eexpr with