feat: Drop Debug requirements and flip implementation defaults (#756)

Author: Veykril

benches/compare.rs

@@ -26,7 +26,7 @@ pub struct InternedInput<'db> {
     pub text: String,
 }
 
-#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, salsa::Supertype)]
+#[derive(Clone, Copy, PartialEq, Eq, Hash, salsa::Supertype)]
 enum SupertypeInput<'db> {
     InternedInput(InternedInput<'db>),
     Input(Input),

components/salsa-macro-rules/src/setup_input_struct.rs

@@ -223,7 +223,12 @@ macro_rules! setup_input_struct {
                 }
 
                 /// Default debug formatting for this struct (may be useful if you define your own `Debug` impl)
-                pub fn default_debug_fmt(this: Self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+                pub fn default_debug_fmt(this: Self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result
+                where
+                    // rustc rejects trivial bounds, but it cannot see through higher-ranked bounds
+                    // with its check :^)
+                    $(for<'__trivial_bounds> $field_ty: std::fmt::Debug),*
+                {
                     $zalsa::with_attached_database(|db| {
                         let fields = $Configuration::ingredient(db).leak_fields(db, this);
                         let mut f = f.debug_struct(stringify!($Struct));

components/salsa-macro-rules/src/setup_tracked_struct.rs

@@ -286,9 +286,18 @@ macro_rules! setup_tracked_struct {
                         )
                     }
                 )*
+            }
 
+            impl<'_db> $Struct<'_db> {
                 /// Default debug formatting for this struct (may be useful if you define your own `Debug` impl)
-                pub fn default_debug_fmt(this: Self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+                pub fn default_debug_fmt(this: Self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result
+                where
+                    // `zalsa::with_attached_database` has a local lifetime for the database
+                    // so we need this function to be higher-ranked over the db lifetime
+                    // Thus the actual lifetime of `Self` does not matter here so we discard
+                    // it with the `'_db` lifetime name as we cannot shadow lifetimes.
+                    $(for<$db_lt> $field_ty: std::fmt::Debug),*
+                {
                     $zalsa::with_attached_database(|db| {
                         let fields = $Configuration::ingredient(db).leak_fields(db, this);
                         let mut f = f.debug_struct(stringify!($Struct));

components/salsa-macros/src/accumulator.rs

@@ -19,7 +19,7 @@ pub(crate) fn accumulator(
     let ident = struct_item.ident.clone();
     let m = StructMacro {
         hygiene,
-        args,
+        _args: args,
         struct_item,
     };
     match m.try_expand() {
@@ -34,8 +34,8 @@ impl AllowedOptions for Accumulator {
     const RETURN_REF: bool = false;
     const SPECIFY: bool = false;
     const NO_EQ: bool = false;
-    const NO_DEBUG: bool = true;
-    const NO_CLONE: bool = true;
+    const DEBUG: bool = false;
+    const NO_CLONE: bool = false;
     const NO_LIFETIME: bool = false;
     const SINGLETON: bool = false;
     const DATA: bool = false;
@@ -49,7 +49,7 @@ impl AllowedOptions for Accumulator {
 
 struct StructMacro {
     hygiene: Hygiene,
-    args: Options<Accumulator>,
+    _args: Options<Accumulator>,
     struct_item: syn::ItemStruct,
 }
 
@@ -65,16 +65,7 @@ impl StructMacro {
 
         let struct_item = self.struct_item;
 
-        let mut derives = vec![];
-        if self.args.no_debug.is_none() {
-            derives.push(quote!(Debug));
-        }
-        if self.args.no_clone.is_none() {
-            derives.push(quote!(Clone));
-        }
-
         Ok(quote! {
-            #[derive(#(#derives),*)]
             #struct_item
 
             salsa::plumbing::setup_accumulator_impl! {

components/salsa-macros/src/input.rs

@@ -40,7 +40,7 @@ impl crate::options::AllowedOptions for InputStruct {
 
     const NO_EQ: bool = false;
 
-    const NO_DEBUG: bool = true;
+    const DEBUG: bool = true;
 
     const NO_LIFETIME: bool = false;
 

components/salsa-macros/src/interned.rs

@@ -41,7 +41,7 @@ impl crate::options::AllowedOptions for InternedStruct {
 
     const NO_EQ: bool = false;
 
-    const NO_DEBUG: bool = true;
+    const DEBUG: bool = true;
 
     const NO_LIFETIME: bool = true;
 

components/salsa-macros/src/options.rs

@@ -20,10 +20,10 @@ pub(crate) struct Options<A: AllowedOptions> {
     /// If this is `Some`, the value is the `no_eq` identifier.
     pub no_eq: Option<syn::Ident>,
 
-    /// Signal we should not generate a `Debug` impl.
+    /// Signal we should generate a `Debug` impl.
     ///
-    /// If this is `Some`, the value is the `no_debug` identifier.
-    pub no_debug: Option<syn::Ident>,
+    /// If this is `Some`, the value is the `debug` identifier.
+    pub debug: Option<syn::Ident>,
 
     /// Signal we should not include the `'db` lifetime.
     ///
@@ -93,7 +93,7 @@ impl<A: AllowedOptions> Default for Options<A> {
             return_ref: Default::default(),
             specify: Default::default(),
             no_eq: Default::default(),
-            no_debug: Default::default(),
+            debug: Default::default(),
             no_lifetime: Default::default(),
             no_clone: Default::default(),
             db_path: Default::default(),
@@ -114,7 +114,7 @@ pub(crate) trait AllowedOptions {
     const RETURN_REF: bool;
     const SPECIFY: bool;
     const NO_EQ: bool;
-    const NO_DEBUG: bool;
+    const DEBUG: bool;
     const NO_LIFETIME: bool;
     const NO_CLONE: bool;
     const SINGLETON: bool;
@@ -161,18 +161,15 @@ impl<A: AllowedOptions> syn::parse::Parse for Options<A> {
                         "`no_eq` option not allowed here",
                     ));
                 }
-            } else if ident == "no_debug" {
-                if A::NO_DEBUG {
-                    if let Some(old) = options.no_debug.replace(ident) {
-                        return Err(syn::Error::new(
-                            old.span(),
-                            "option `no_debug` provided twice",
-                        ));
+            } else if ident == "debug" {
+                if A::DEBUG {
+                    if let Some(old) = options.debug.replace(ident) {
+                        return Err(syn::Error::new(old.span(), "option `debug` provided twice"));
                     }
                 } else {
                     return Err(syn::Error::new(
                         ident.span(),
-                        "`no_debug` option not allowed here",
+                        "`debug` option not allowed here",
                     ));
                 }
             } else if ident == "no_lifetime" {

components/salsa-macros/src/salsa_struct.rs

@@ -330,7 +330,7 @@ where
     }
 
     pub fn generate_debug_impl(&self) -> bool {
-        self.args.no_debug.is_none()
+        self.args.debug.is_some()
     }
 
     pub fn generate_lifetime(&self) -> bool {

components/salsa-macros/src/tracked_fn.rs

@@ -29,7 +29,7 @@ impl crate::options::AllowedOptions for TrackedFn {
 
     const NO_EQ: bool = true;
 
-    const NO_DEBUG: bool = false;
+    const DEBUG: bool = false;
 
     const NO_LIFETIME: bool = false;
 

components/salsa-macros/src/tracked_struct.rs

@@ -35,7 +35,7 @@ impl crate::options::AllowedOptions for TrackedStruct {
 
     const NO_EQ: bool = false;
 
-    const NO_DEBUG: bool = true;
+    const DEBUG: bool = true;
 
     const NO_LIFETIME: bool = false;