Add support for const_into_str attribute to enable static string co…

…nversions in const contexts resolves: Peternator7#352
debridge-finance · Apr 26, 2024 · 07804d0 · 07804d0
1 parent 410062e
commit 07804d0
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Showing 3 changed files with 38 additions and 1 deletion.
diff --git a/strum_macros/src/helpers/metadata.rs b/strum_macros/src/helpers/metadata.rs
@@ -16,6 +16,7 @@ pub mod kw {
 
     // enum metadata
     custom_keyword!(serialize_all);
+    custom_keyword!(const_into_str);
     custom_keyword!(use_phf);
     custom_keyword!(prefix);
 
@@ -51,6 +52,7 @@ pub enum EnumMeta {
         kw: kw::prefix,
         prefix: LitStr,
     },
+    ConstIntoStr(kw::const_into_str)
 }
 
 impl Parse for EnumMeta {
@@ -80,6 +82,8 @@ impl Parse for EnumMeta {
             input.parse::<Token![=]>()?;
             let prefix = input.parse()?;
             Ok(EnumMeta::Prefix { kw, prefix })
+        } else if lookahead.peek(kw::const_into_str) {
+            Ok(EnumMeta::ConstIntoStr(input.parse()?))
         } else {
             Err(lookahead.error())
         }

diff --git a/strum_macros/src/helpers/type_props.rs b/strum_macros/src/helpers/type_props.rs
@@ -23,6 +23,7 @@ pub struct StrumTypeProperties {
     pub use_phf: bool,
     pub prefix: Option<LitStr>,
     pub enum_repr: Option<TokenStream>,
+    pub const_into_str: bool,
 }
 
 impl HasTypeProperties for DeriveInput {
@@ -37,6 +38,8 @@ impl HasTypeProperties for DeriveInput {
         let mut use_phf_kw = None;
         let mut crate_module_path_kw = None;
         let mut prefix_kw = None;
+        let mut const_into_str = None;
+
         for meta in strum_meta {
             match meta {
                 EnumMeta::SerializeAll { case_style, kw } => {
@@ -82,6 +85,14 @@ impl HasTypeProperties for DeriveInput {
                     prefix_kw = Some(kw);
                     output.prefix = Some(prefix);
                 }
+                EnumMeta::ConstIntoStr(kw) => {
+                    if let Some(fst_kw) = const_into_str {
+                        return Err(occurrence_error(fst_kw, kw, "const_into_str"));
+                    }
+
+                    const_into_str = Some(kw);
+                    output.const_into_str = true;
+                }
             }
         }
 

diff --git a/strum_macros/src/macros/strings/as_ref_str.rs b/strum_macros/src/macros/strings/as_ref_str.rs
@@ -99,7 +99,7 @@ pub fn as_static_str_inner(
                 }
             }
         },
-        GenerateTraitVariant::From => quote! {
+        GenerateTraitVariant::From if !type_properties.const_into_str => quote! {
             impl #impl_generics ::core::convert::From<#name #ty_generics> for &'static str #where_clause {
                 fn from(x: #name #ty_generics) -> &'static str {
                     match x {
@@ -115,5 +115,27 @@ pub fn as_static_str_inner(
                 }
             }
         },
+        GenerateTraitVariant::From  => quote! {
+            impl #name #ty_generics {
+                pub const fn into_str(&self) -> &'static str #where_clause {
+                    match *self {
+                        #(#arms3),*
+                    }
+                }
+            }
+
+            impl #impl_generics ::core::convert::From<#name #ty_generics> for &'static str #where_clause {
+                fn from(x: #name #ty_generics) -> &'static str {
+                    match x {
+                        #(#arms2),*
+                    }
+                }
+            }
+            impl #impl_generics2 ::core::convert::From<&'_derivative_strum #name #ty_generics> for &'static str #where_clause {
+                fn from(x: &'_derivative_strum #name #ty_generics) -> &'static str {
+                    x.into_str()
+                }
+            }
+        },
     })
 }