1 files changed, 182 insertions, 0 deletions
diff --git a/crates/elfmacros/src/lib.rs b/crates/elfmacros/src/lib.rs
index e69de29..e7f05a2 100644
--- a/crates/elfmacros/src/lib.rs
+++ b/crates/elfmacros/src/lib.rs
@@ -0,0 +1,182 @@
+use proc_macro2::TokenStream;
+use quote::{quote, TokenStreamExt};
+
+fn title_to_kebab_case(s: &str) -> String {
+    let mut ret = String::new();
+    let mut start = 0;
+    for (end, _) in s.match_indices(|c: char| c.is_ascii_uppercase()) {
+        if start != end {
+            ret.push_str(&s[start..end].to_ascii_lowercase());
+            ret.push_str("-");
+        }
+        start = end;
+    }
+    ret.push_str(&s[start..].to_ascii_lowercase());
+    // s.split_inclusive(|c: char| c.is_ascii_uppercase())
+        //     .map(|s| s.to_ascii_lowercase())
+        //     .join("-")
+    ret
+}
+
+#[proc_macro_derive(Unifiable)]
+pub fn derive_unifiable(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
+    let input = syn::parse_macro_input!(input as syn::DeriveInput);
+    let name = input.ident;
+    let en = if let syn::Data::Enum(e) = &input.data { e } else {
+        return proc_macro::TokenStream::from(quote! { compile_error!("can only derive unifiable for an enum"); })
+    };
+    let mut cases = TokenStream::new();
+    for v in en.variants.iter() {
+        let vnm = &v.ident;
+        cases.append_all(
+            quote! {
+                (Self :: #vnm (a), Self::Concrete:: #vnm (b) ) => a.unify(b, u),
+            },
+        );
+    }
+    let expanded = quote! {
+        impl crate::knowledge::Unifiable for #name {
+            fn unify(&self, other: &Self::Concrete, u: crate::knowledge::Unification) -> Option<crate::knowledge::Unification> {
+                match (self, other) {
+                    #cases
+                    _ => None,
+                }
+            }
+        }
+    };
+    proc_macro::TokenStream::from(expanded)
+}
+
+#[proc_macro_derive(Substitutable)]
+pub fn derive_substitutable(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
+    let input = syn::parse_macro_input!(input as syn::DeriveInput);
+    let name = input.ident;
+    let en = if let syn::Data::Enum(e) = &input.data { e } else {
+        return proc_macro::TokenStream::from(quote! { compile_error!("can only derive substitutable for an enum"); })
+    };
+    let mut subcases = TokenStream::new();
+    let mut mvcases = TokenStream::new();
+    for v in en.variants.iter() {
+        let vnm = &v.ident;
+        subcases.append_all(
+            quote! {
+                Self :: #vnm (x) => Self :: #vnm (x.substitute(u)),
+            },
+        );
+        mvcases.append_all(
+            quote! {
+                Self :: #vnm (x) => Self :: #vnm (x.map_variables(f)),
+            },
+        );
+    }
+    let expanded = quote! {
+        impl crate::knowledge::Substitutable for #name {
+            fn substitute(&self, u: &crate::knowledge::Unification) -> Self {
+                match self {
+                    #subcases
+                }
+            }
+            fn map_variables<F>(&self, f: &mut F) -> Self where F: FnMut(crate::knowledge::Var) -> Var {
+                match self {
+                    #mvcases
+                }
+            }
+        }
+    };
+    proc_macro::TokenStream::from(expanded)
+}
+
+#[proc_macro_derive(Concrete)]
+pub fn derive_concrete(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
+    let input = syn::parse_macro_input!(input as syn::DeriveInput);
+    let name = input.ident;
+    let en = if let syn::Data::Enum(e) = &input.data { e } else {
+        return proc_macro::TokenStream::from(quote! { compile_error!("can only derive concretizable for an enum"); })
+    };
+    let hnm = syn::Ident::new(&format!("{}Hole", name), name.span());
+    let dnm = syn::Ident::new(&format!("{}Discriminants", name), name.span());
+    let mut cases = TokenStream::new();
+    let mut dcases = TokenStream::new();
+    let mut dispcases = TokenStream::new();
+    let mut variants = TokenStream::new();
+    for v in en.variants.iter() {
+        let vnm = &v.ident;
+        let kebab = title_to_kebab_case(&vnm.to_string());
+        let mut vtypes = TokenStream::new();
+        let mut tuple = false;
+        if let syn::Fields::Unnamed(fu) = &v.fields {
+            for f in fu.unnamed.iter() {
+                if let syn::Type::Tuple(tu) = &f.ty {
+                    tuple = true;
+                    for tty in tu.elems.iter() {
+                        vtypes.append_all(quote! {
+                            crate::knowledge::Hole < #tty > ,
+                        });
+                    }
+                } else {
+                    let vty = &f.ty;
+                    vtypes.append_all(quote! {
+                            crate::knowledge::Hole < #vty > ,
+                    });
+                }
+            }
+        }
+        if tuple {
+            variants.append_all(quote! {
+                #vnm (( #vtypes )) ,
+            });
+        } else {
+            variants.append_all(quote! {
+                #vnm ( #vtypes ) ,
+            });
+        }
+        cases.append_all(quote! {
+            Self :: #vnm (a) => Some( #name :: #vnm ( a.concretize()? )) ,
+        });
+        dcases.append_all(quote! {
+            Self :: #vnm {..} => #dnm :: #vnm ,
+        });
+        dispcases.append_all(
+            quote! {
+                Self :: #vnm (x) => { write!(f, "{}", #kebab)?; x.display_tuple(f) },
+            },
+        );
+    }
+    let expanded = quote! {
+        #[derive(Debug, Clone, PartialEq, Eq, Hash, elfmacros::Unifiable, elfmacros::Substitutable)]
+        pub enum #hnm {
+            #variants
+        }
+        impl crate::knowledge::Concretizable for #hnm {
+            type Concrete = #name;
+            fn concretize(&self) -> Option<Self::Concrete> {
+                match self {
+                    #cases
+                    _ => None,
+                }
+            }
+        }
+        impl #hnm {
+            pub fn discriminant(&self) -> #dnm {
+                match self {
+                    #dcases
+                }
+            }
+        }
+        impl std::fmt::Display for #hnm {
+            fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+                match self {
+                    #dispcases
+                }
+            }
+        }
+        impl std::fmt::Display for #name {
+            fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+                match self {
+                    #dispcases
+                }
+            }
+        }
+    };
+    proc_macro::TokenStream::from(expanded)
+}