Enum variant discriminants hints

crates/rust-analyzer/src/config.rs

@@ -327,6 +327,8 @@ config_data! {
         inlayHints_closingBraceHints_minLines: usize               = "25",
         /// Whether to show inlay type hints for return types of closures.
         inlayHints_closureReturnTypeHints_enable: ClosureReturnTypeHintsDef  = "\"never\"",
+        /// Whether to show enum variant discriminant hints.
+        inlayHints_discriminantHints_enable: DiscriminantHintsDef            = "\"never\"",
         /// Whether to show inlay hints for type adjustments.
         inlayHints_expressionAdjustmentHints_enable: AdjustmentHintsDef = "\"never\"",
         /// Whether to hide inlay hints for type adjustments outside of `unsafe` blocks.
@@ -1218,6 +1220,11 @@ impl Config {
             type_hints: self.data.inlayHints_typeHints_enable,
             parameter_hints: self.data.inlayHints_parameterHints_enable,
             chaining_hints: self.data.inlayHints_chainingHints_enable,
+            discriminant_hints: match self.data.inlayHints_discriminantHints_enable {
+                DiscriminantHintsDef::Always => ide::DiscriminantHints::Always,
+                DiscriminantHintsDef::Never => ide::DiscriminantHints::Never,
+                DiscriminantHintsDef::Fieldless => ide::DiscriminantHints::Fieldless,
+            },
             closure_return_type_hints: match self.data.inlayHints_closureReturnTypeHints_enable {
                 ClosureReturnTypeHintsDef::Always => ide::ClosureReturnTypeHints::Always,
                 ClosureReturnTypeHintsDef::Never => ide::ClosureReturnTypeHints::Never,
@@ -1579,6 +1586,7 @@ mod de_unit_v {
     named_unit_variant!(skip_trivial);
     named_unit_variant!(mutable);
     named_unit_variant!(reborrow);
+    named_unit_variant!(fieldless);
     named_unit_variant!(with_block);
 }
 
@@ -1742,6 +1750,17 @@ enum AdjustmentHintsDef {
     Reborrow,
 }
 
+#[derive(Deserialize, Debug, Clone)]
+#[serde(untagged)]
+enum DiscriminantHintsDef {
+    #[serde(deserialize_with = "true_or_always")]
+    Always,
+    #[serde(deserialize_with = "false_or_never")]
+    Never,
+    #[serde(deserialize_with = "de_unit_v::fieldless")]
+    Fieldless,
+}
+
 #[derive(Deserialize, Debug, Clone)]
 #[serde(rename_all = "snake_case")]
 enum FilesWatcherDef {
@@ -2064,6 +2083,19 @@ fn field_props(field: &str, ty: &str, doc: &[&str], default: &str) -> serde_json
                 "Only show auto borrow and dereference adjustment hints."
             ]
         },
+        "DiscriminantHintsDef" => set! {
+            "type": "string",
+            "enum": [
+                "always",
+                "never",
+                "fieldless"
+            ],
+            "enumDescriptions": [
+                "Always show all discriminant hints.",
+                "Never show discriminant hints.",
+                "Only show discriminant hints on fieldless enum variants."
+            ]
+        },
         "CargoFeaturesDef" => set! {
             "anyOf": [
                 {

crates/rust-analyzer/src/to_proto.rs

@@ -434,6 +434,7 @@ pub(crate) fn inlay_hint(
         InlayKind::ParameterHint if render_colons => inlay_hint.label.append_str(":"),
         InlayKind::TypeHint if render_colons => inlay_hint.label.prepend_str(": "),
         InlayKind::ClosureReturnTypeHint => inlay_hint.label.prepend_str(" -> "),
+        InlayKind::DiscriminantHint => inlay_hint.label.prepend_str(" = "),
         _ => {}
     }
 
@@ -447,6 +448,7 @@ pub(crate) fn inlay_hint(
             // after annotated thing
             InlayKind::ClosureReturnTypeHint
             | InlayKind::TypeHint
+            | InlayKind::DiscriminantHint
             | InlayKind::ChainingHint
             | InlayKind::GenericParamListHint
             | InlayKind::ClosingParenthesis
@@ -457,6 +459,7 @@ pub(crate) fn inlay_hint(
             InlayKind::TypeHint => !render_colons,
             InlayKind::ChainingHint | InlayKind::ClosingBraceHint => true,
             InlayKind::ClosingParenthesis
+            | InlayKind::DiscriminantHint
             | InlayKind::OpeningParenthesis
             | InlayKind::BindingModeHint
             | InlayKind::ClosureReturnTypeHint
@@ -473,6 +476,7 @@ pub(crate) fn inlay_hint(
             | InlayKind::GenericParamListHint
             | InlayKind::AdjustmentHint
             | InlayKind::TypeHint
+            | InlayKind::DiscriminantHint
             | InlayKind::ClosingBraceHint => false,
             InlayKind::BindingModeHint => inlay_hint.label.as_simple_str() != Some("&"),
             InlayKind::ParameterHint | InlayKind::LifetimeHint => true,
@@ -483,6 +487,7 @@ pub(crate) fn inlay_hint(
                 Some(lsp_types::InlayHintKind::TYPE)
             }
             InlayKind::ClosingParenthesis
+            | InlayKind::DiscriminantHint
             | InlayKind::OpeningParenthesis
             | InlayKind::BindingModeHint
             | InlayKind::GenericParamListHint