Improvements to test coverage (#340)

This increases msrv to 1.70

schemars_derive/Cargo.toml

@@ -10,7 +10,7 @@ license = "MIT"
 readme = "README.md"
 keywords = ["rust", "json-schema", "serde"]
 categories = ["encoding", "no-std"]
-rust-version = "1.65"
+rust-version = "1.70"
 
 [lib]
 proc-macro = true

schemars_derive/src/lib.rs

@@ -126,7 +126,10 @@ fn derive_json_schema(mut input: syn::DeriveInput, repr: bool) -> syn::Result<To
         (
             quote! {
                 schemars::_private::alloc::borrow::Cow::Owned(
-                    schemars::_private::alloc::format!(#schema_name_fmt #(,#type_params=#type_params::schema_name())* #(,#const_params=#const_params)*)
+                    schemars::_private::alloc::format!(
+                        #schema_name_fmt
+                        #(,#type_params=#type_params::schema_name())*
+                        #(,#const_params=schemars::_private::alloc::string::ToString::to_string(&#const_params))*)
                 )
             },
             quote! {