1 files changed, 155 insertions, 0 deletions
diff --git a/rust/macros/helpers.rs b/rust/macros/helpers.rs
new file mode 100644
index 0000000000..afb0f2e3a3
--- /dev/null
+++ b/rust/macros/helpers.rs
@@ -0,0 +1,155 @@
+// SPDX-License-Identifier: GPL-2.0
+
+use proc_macro::{token_stream, Group, Punct, Spacing, TokenStream, TokenTree};
+
+pub(crate) fn try_ident(it: &mut token_stream::IntoIter) -> Option<String> {
+    if let Some(TokenTree::Ident(ident)) = it.next() {
+        Some(ident.to_string())
+    } else {
+        None
+    }
+}
+
+pub(crate) fn try_literal(it: &mut token_stream::IntoIter) -> Option<String> {
+    if let Some(TokenTree::Literal(literal)) = it.next() {
+        Some(literal.to_string())
+    } else {
+        None
+    }
+}
+
+pub(crate) fn try_string(it: &mut token_stream::IntoIter) -> Option<String> {
+    try_literal(it).and_then(|string| {
+        if string.starts_with('\"') && string.ends_with('\"') {
+            let content = &string[1..string.len() - 1];
+            if content.contains('\\') {
+                panic!("Escape sequences in string literals not yet handled");
+            }
+            Some(content.to_string())
+        } else if string.starts_with("r\"") {
+            panic!("Raw string literals are not yet handled");
+        } else {
+            None
+        }
+    })
+}
+
+pub(crate) fn expect_ident(it: &mut token_stream::IntoIter) -> String {
+    try_ident(it).expect("Expected Ident")
+}
+
+pub(crate) fn expect_punct(it: &mut token_stream::IntoIter) -> char {
+    if let TokenTree::Punct(punct) = it.next().expect("Reached end of token stream for Punct") {
+        punct.as_char()
+    } else {
+        panic!("Expected Punct");
+    }
+}
+
+pub(crate) fn expect_string(it: &mut token_stream::IntoIter) -> String {
+    try_string(it).expect("Expected string")
+}
+
+pub(crate) fn expect_string_ascii(it: &mut token_stream::IntoIter) -> String {
+    let string = try_string(it).expect("Expected string");
+    assert!(string.is_ascii(), "Expected ASCII string");
+    string
+}
+
+pub(crate) fn expect_group(it: &mut token_stream::IntoIter) -> Group {
+    if let TokenTree::Group(group) = it.next().expect("Reached end of token stream for Group") {
+        group
+    } else {
+        panic!("Expected Group");
+    }
+}
+
+pub(crate) fn expect_end(it: &mut token_stream::IntoIter) {
+    if it.next().is_some() {
+        panic!("Expected end");
+    }
+}
+
+pub(crate) struct Generics {
+    pub(crate) impl_generics: Vec<TokenTree>,
+    pub(crate) ty_generics: Vec<TokenTree>,
+}
+
+/// Parses the given `TokenStream` into `Generics` and the rest.
+///
+/// The generics are not present in the rest, but a where clause might remain.
+pub(crate) fn parse_generics(input: TokenStream) -> (Generics, Vec<TokenTree>) {
+    // `impl_generics`, the declared generics with their bounds.
+    let mut impl_generics = vec![];
+    // Only the names of the generics, without any bounds.
+    let mut ty_generics = vec![];
+    // Tokens not related to the generics e.g. the `where` token and definition.
+    let mut rest = vec![];
+    // The current level of `<`.
+    let mut nesting = 0;
+    let mut toks = input.into_iter();
+    // If we are at the beginning of a generic parameter.
+    let mut at_start = true;
+    for tt in &mut toks {
+        match tt.clone() {
+            TokenTree::Punct(p) if p.as_char() == '<' => {
+                if nesting >= 1 {
+                    // This is inside of the generics and part of some bound.
+                    impl_generics.push(tt);
+                }
+                nesting += 1;
+            }
+            TokenTree::Punct(p) if p.as_char() == '>' => {
+                // This is a parsing error, so we just end it here.
+                if nesting == 0 {
+                    break;
+                } else {
+                    nesting -= 1;
+                    if nesting >= 1 {
+                        // We are still inside of the generics and part of some bound.
+                        impl_generics.push(tt);
+                    }
+                    if nesting == 0 {
+                        break;
+                    }
+                }
+            }
+            tt => {
+                if nesting == 1 {
+                    // Here depending on the token, it might be a generic variable name.
+                    match &tt {
+                        // Ignore const.
+                        TokenTree::Ident(i) if i.to_string() == "const" => {}
+                        TokenTree::Ident(_) if at_start => {
+                            ty_generics.push(tt.clone());
+                            // We also already push the `,` token, this makes it easier to append
+                            // generics.
+                            ty_generics.push(TokenTree::Punct(Punct::new(',', Spacing::Alone)));
+                            at_start = false;
+                        }
+                        TokenTree::Punct(p) if p.as_char() == ',' => at_start = true,
+                        // Lifetimes begin with `'`.
+                        TokenTree::Punct(p) if p.as_char() == '\'' && at_start => {
+                            ty_generics.push(tt.clone());
+                        }
+                        _ => {}
+                    }
+                }
+                if nesting >= 1 {
+                    impl_generics.push(tt);
+                } else if nesting == 0 {
+                    // If we haven't entered the generics yet, we still want to keep these tokens.
+                    rest.push(tt);
+                }
+            }
+        }
+    }
+    rest.extend(toks);
+    (
+        Generics {
+            impl_generics,
+            ty_generics,
+        },
+        rest,
+    )
+}