identifiers: Add session_id macro

crates/ruma-common/src/identifiers.rs

@@ -161,6 +161,19 @@ macro_rules! server_name {
     };
 }
 
+/// Compile-time checked `SessionId` construction.
+#[macro_export]
+macro_rules! session_id {
+    ($s:literal) => {{
+        const SESSION_ID: &$crate::SessionId = match $crate::SessionId::_priv_const_new($s) {
+            Ok(id) => id,
+            Err(_) => panic!("Invalid session ID"),
+        };
+
+        SESSION_ID
+    }};
+}
+
 /// Compile-time checked `MxcUri` construction.
 #[macro_export]
 macro_rules! mxc_uri {

crates/ruma-common/src/identifiers/session_id.rs

@@ -13,6 +13,16 @@ use super::IdParseError;
 #[ruma_id(validate = validate_session_id)]
 pub struct SessionId(str);
 
+impl SessionId {
+    #[doc(hidden)]
+    pub const fn _priv_const_new(s: &str) -> Result<&Self, IdParseError> {
+        match validate_session_id(s) {
+            Ok(()) => Ok(Self::from_borrowed(s)),
+            Err(e) => Err(e),
+        }
+    }
+}
+
 const fn validate_session_id(s: &str) -> Result<(), IdParseError> {
     if s.len() > 255 {
         return Err(IdParseError::MaximumLengthExceeded);

crates/ruma-common/tests/identifiers/id_macros.rs

@@ -3,4 +3,5 @@ fn ui() {
     let t = trybuild::TestCases::new();
     t.pass("tests/identifiers/ui/01-valid-id-macros.rs");
     t.compile_fail("tests/identifiers/ui/02-invalid-id-macros.rs");
+    t.compile_fail("tests/identifiers/ui/03-invalid-new-id-macros.rs");
 }

crates/ruma-common/tests/identifiers/ui/03-invalid-new-id-macros.rs

@@ -0,0 +1,3 @@
+fn main() {
+    let _ = ruma_common::session_id!("invalid~");
+}

crates/ruma-common/tests/identifiers/ui/03-invalid-new-id-macros.stderr

@@ -0,0 +1,7 @@
+error[E0080]: evaluation of constant value failed
+ --> tests/identifiers/ui/03-invalid-new-id-macros.rs:2:13
+  |
+2 |     let _ = ruma_common::session_id!("invalid~");
+  |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'Invalid session ID', $DIR/tests/identifiers/ui/03-invalid-new-id-macros.rs:2:13
+  |
+  = note: this error originates in the macro `$crate::panic::panic_2021` (in Nightly builds, run with -Z macro-backtrace for more info)

crates/ruma-macros/src/identifiers.rs

@@ -78,7 +78,7 @@ pub fn expand_id_zst(input: ItemStruct) -> syn::Result<TokenStream> {
         #owned_decl
 
         impl #impl_generics #id_ty {
-            pub(super) fn from_borrowed(s: &str) -> &Self {
+            pub(super) const fn from_borrowed(s: &str) -> &Self {
                 unsafe { std::mem::transmute(s) }
             }