Add internal '__typed_stream' proc-macro.

This resolves syntax ambiguity issues with public typed-stream macros.
Prior to this commit, greedy single-token matching by macro-rules macros
would result in certain tokens at the beginning of the macro input, such
as 'for', inadvertently triggering a '$ty' matching case resulting in
incorrect expansion.

core/codegen/src/bang/mod.rs

@@ -1,12 +1,13 @@
-use devise::Result;
-use syn::{Path, punctuated::Punctuated, parse::Parser, Token};
-use syn::spanned::Spanned;
-use proc_macro2::TokenStream;
-
 mod uri;
 mod uri_parsing;
 mod test_guide;
 mod export;
+mod typed_stream;
+
+use devise::Result;
+use syn::{Path, punctuated::Punctuated, parse::Parser, Token};
+use syn::spanned::Spanned;
+use proc_macro2::TokenStream;
 
 fn struct_maker_vec(
     input: proc_macro::TokenStream,
@@ -70,3 +71,8 @@ pub fn export_internal(input: proc_macro::TokenStream) -> TokenStream {
     export::_macro(input)
         .unwrap_or_else(|diag| diag.emit_as_item_tokens())
 }
+
+pub fn typed_stream(input: proc_macro::TokenStream) -> TokenStream {
+    typed_stream::_macro(input)
+        .unwrap_or_else(|diag| diag.emit_as_item_tokens())
+}

core/codegen/src/bang/typed_stream.rs

@@ -0,0 +1,53 @@
+use proc_macro2::TokenStream;
+use syn::parse::{Parse, ParseStream, discouraged::Speculative};
+
+enum Input {
+    Type(syn::Type),
+    Tokens(TokenStream)
+}
+
+struct Invocation {
+    ty_stream_ty: syn::Path,
+    stream_mac: syn::Path,
+    stream_trait: syn::Path,
+    input: Input,
+}
+
+impl Parse for Invocation {
+    fn parse(input: ParseStream<'_>) -> syn::Result<Self> {
+        let ty_stream_ty = input.parse()?;
+        input.parse::<syn::Token![,]>()?;
+
+        let stream_mac = input.parse()?;
+        input.parse::<syn::Token![,]>()?;
+
+        let stream_trait = input.parse()?;
+        input.parse::<syn::Token![,]>()?;
+
+        let fork = input.fork();
+        let input = match fork.parse() {
+            Ok(ty) => {
+                input.advance_to(&fork);
+                Input::Type(ty)
+            }
+            Err(_) => Input::Tokens(input.parse()?)
+        };
+
+        Ok(Invocation { ty_stream_ty, stream_mac, stream_trait, input })
+    }
+}
+
+/// This macro exists because we want to disambiguate between input of a type
+/// and input of an expression that looks like a type. `macro_rules` matches
+/// eagerly on a single token, so something like `foo!(for x in 0..10 {})` will
+/// match a `($ty)` branch as will anything that starts with a path.
+pub fn _macro(input: proc_macro::TokenStream) -> devise::Result<TokenStream> {
+    let i: Invocation = syn::parse(input)?;
+    let (s_ty, mac, s_trait) = (i.ty_stream_ty, i.stream_mac, i.stream_trait);
+    let tokens = match i.input {
+        Input::Tokens(tt) => quote!(#s_ty::from(#mac!(#tt))),
+        Input::Type(ty) => quote!(#s_ty<impl #s_trait<Item = #ty>>),
+    };
+
+    Ok(tokens)
+}

core/codegen/src/lib.rs

@@ -1345,23 +1345,30 @@ pub fn uri(input: TokenStream) -> TokenStream {
     emit!(bang::uri_macro(input))
 }
 
-#[doc(hidden)]
-#[proc_macro]
 /// Internal macro: `rocket_internal_uri!`.
+#[proc_macro]
+#[doc(hidden)]
 pub fn rocket_internal_uri(input: TokenStream) -> TokenStream {
     emit!(bang::uri_internal_macro(input))
 }
 
-#[doc(hidden)]
+/// Internal macro: `__typed_stream!`.
 #[proc_macro]
+#[doc(hidden)]
+pub fn __typed_stream(input: TokenStream) -> TokenStream {
+    emit!(bang::typed_stream(input))
+}
+
 /// Private Rocket internal macro: `internal_guide_tests!`.
+#[proc_macro]
+#[doc(hidden)]
 pub fn internal_guide_tests(input: TokenStream) -> TokenStream {
     emit!(bang::guide_tests_internal(input))
 }
 
-#[doc(hidden)]
-#[proc_macro]
 /// Private Rocket internal macro: `export!`.
+#[proc_macro]
+#[doc(hidden)]
 pub fn export(input: TokenStream) -> TokenStream {
     emit!(bang::export_internal(input))
 }

core/codegen/tests/catcher.rs

@@ -7,7 +7,7 @@
 
 use rocket::{Request, Rocket, Build};
 use rocket::local::blocking::Client;
-use rocket::http::{Status, ContentType};
+use rocket::http::Status;
 
 #[catch(404)] fn not_found_0() -> &'static str { "404-0" }
 #[catch(404)] fn not_found_1(_: &Request) -> &'static str { "404-1" }

core/lib/src/response/stream/bytes.rs

@@ -78,7 +78,6 @@ crate::export! {
     /// See [`struct@ByteStream`] and the [module level
     /// docs](crate::response::stream#typed-streams) for usage details.
     macro_rules! ByteStream {
-        ($T:ty) => ($crate::_typed_stream!(ByteStream, $T));
         ($($s:tt)*) => ($crate::_typed_stream!(ByteStream, $($s)*));
     }
 }

core/lib/src/response/stream/mod.rs

@@ -223,10 +223,12 @@ crate::export! {
 #[doc(hidden)]
 #[macro_export]
 macro_rules! _typed_stream {
-    ($S:ident, $T:ty) => (
-        $crate::response::stream::$S<impl $crate::futures::stream::Stream<Item = $T>>
-    );
     ($S:ident, $($t:tt)*) => (
-        $crate::response::stream::$S::from($crate::response::stream::stream!($($t)*))
-    );
+        $crate::__typed_stream! {
+            $crate::response::stream::$S,
+            $crate::response::stream::stream,
+            $crate::futures::stream::Stream,
+            $($t)*
+        }
+    )
 }

core/lib/src/response/stream/reader.rs

@@ -199,7 +199,6 @@ crate::export! {
     /// See [`struct@ReaderStream`] and the [module level
     /// docs](crate::response::stream#typed-streams) for usage details.
     macro_rules! ReaderStream {
-        ($T:ty) => ($crate::_typed_stream!(ReaderStream, $T));
         ($($s:tt)*) => ($crate::_typed_stream!(ReaderStream, $($s)*));
     }
 }

core/lib/src/response/stream/text.rs

@@ -88,7 +88,6 @@ crate::export! {
     /// See [`struct@TextStream`] and the [module level
     /// docs](crate::response::stream#typed-streams) for usage details.
     macro_rules! TextStream {
-        ($T:ty) => ($crate::_typed_stream!(TextStream, $T));
         ($($s:tt)*) => ($crate::_typed_stream!(TextStream, $($s)*));
     }
 }