Make substitution into a macro.

1 files changed, 4 insertions, 1 deletions

diff --git a/Cargo.toml b/Cargo.toml
index 2fe9469..ae907a5 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -5,9 +5,12 @@ authors = ["Greg Brown <gmb60@cam.ac.uk>"]
 edition = "2018"
 
 [dependencies]
-proc-macro2 = "1.0.24"
 quote = "1.0.7"
 
+[dependencies.proc-macro2]
+version = "1.0.24"
+features = ["span-locations"]
+
 [dependencies.syn]
 version = "1.0.48"
 features = ["extra-traits"]