feat: Allow reborrow inlay hints to be restricted to mutable reborrows only

crates/ide/src/inlay_hints.rs

@@ -19,7 +19,7 @@ pub struct InlayHintsConfig {
     pub type_hints: bool,
     pub parameter_hints: bool,
     pub chaining_hints: bool,
-    pub reborrow_hints: bool,
+    pub reborrow_hints: ReborrowHints,
     pub closure_return_type_hints: bool,
     pub lifetime_elision_hints: LifetimeElisionHints,
     pub param_names_for_lifetime_elision_hints: bool,
@@ -34,6 +34,13 @@ pub enum LifetimeElisionHints {
     Never,
 }
 
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum ReborrowHints {
+    Always,
+    MutableOnly,
+    Never,
+}
+
 #[derive(Clone, Debug, PartialEq, Eq)]
 pub enum InlayKind {
     ChainingHint,
@@ -372,18 +379,20 @@ fn reborrow_hints(
     config: &InlayHintsConfig,
     expr: &ast::Expr,
 ) -> Option<()> {
-    if !config.reborrow_hints {
+    if config.reborrow_hints == ReborrowHints::Never {
         return None;
     }
 
     let mutability = sema.is_implicit_reborrow(expr)?;
+    let label = match mutability {
+        hir::Mutability::Shared if config.reborrow_hints != ReborrowHints::MutableOnly => "&*",
+        hir::Mutability::Mut => "&mut *",
+        _ => return None,
+    };
     acc.push(InlayHint {
         range: expr.syntax().text_range(),
         kind: InlayKind::ImplicitReborrow,
-        label: match mutability {
+        label: SmolStr::new_inline(label),
-            hir::Mutability::Shared => SmolStr::new_inline("&*"),
-            hir::Mutability::Mut => SmolStr::new_inline("&mut *"),
-        },
     });
     Some(())
 }
@@ -848,6 +857,7 @@ mod tests {
     use syntax::{TextRange, TextSize};
     use test_utils::extract_annotations;
 
+    use crate::inlay_hints::ReborrowHints;
     use crate::{fixture, inlay_hints::InlayHintsConfig, LifetimeElisionHints};
 
     const DISABLED_CONFIG: InlayHintsConfig = InlayHintsConfig {
@@ -858,7 +868,7 @@ mod tests {
         lifetime_elision_hints: LifetimeElisionHints::Never,
         hide_named_constructor_hints: false,
         closure_return_type_hints: false,
-        reborrow_hints: false,
+        reborrow_hints: ReborrowHints::Always,
         param_names_for_lifetime_elision_hints: false,
         max_length: None,
     };
@@ -866,7 +876,7 @@ mod tests {
         type_hints: true,
         parameter_hints: true,
         chaining_hints: true,
-        reborrow_hints: true,
+        reborrow_hints: ReborrowHints::Always,
         closure_return_type_hints: true,
         lifetime_elision_hints: LifetimeElisionHints::Always,
         ..DISABLED_CONFIG
@@ -2146,7 +2156,11 @@ impl () {
     #[test]
     fn hints_implicit_reborrow() {
         check_with_config(
-            InlayHintsConfig { reborrow_hints: true, parameter_hints: true, ..DISABLED_CONFIG },
+            InlayHintsConfig {
+                reborrow_hints: ReborrowHints::Always,
+                parameter_hints: true,
+                ..DISABLED_CONFIG
+            },
             r#"
 fn __() {
     let unique = &mut ();

crates/ide/src/lib.rs

@@ -80,7 +80,7 @@ pub use crate::{
     folding_ranges::{Fold, FoldKind},
     highlight_related::{HighlightRelatedConfig, HighlightedRange},
     hover::{HoverAction, HoverConfig, HoverDocFormat, HoverGotoTypeData, HoverResult},
-    inlay_hints::{InlayHint, InlayHintsConfig, InlayKind, LifetimeElisionHints},
+    inlay_hints::{InlayHint, InlayHintsConfig, InlayKind, LifetimeElisionHints, ReborrowHints},
     join_lines::JoinLinesConfig,
     markup::Markup,
     moniker::{MonikerKind, MonikerResult, PackageInformation},

crates/ide/src/static_index.rs

@@ -12,12 +12,10 @@ use ide_db::{
 use syntax::{AstNode, SyntaxKind::*, SyntaxToken, TextRange, T};
 
 use crate::{
-    hover::hover_for_definition, Analysis, Fold, HoverConfig, HoverDocFormat, HoverResult,
+    hover::hover_for_definition,
-    InlayHint, InlayHintsConfig, TryToNav,
-};
-use crate::{
     moniker::{crate_for_file, def_to_moniker, MonikerResult},
-    LifetimeElisionHints,
+    Analysis, Fold, HoverConfig, HoverDocFormat, HoverResult, InlayHint, InlayHintsConfig,
+    TryToNav,
 };
 
 /// A static representation of fully analyzed source code.
@@ -112,8 +110,8 @@ impl StaticIndex<'_> {
                     parameter_hints: true,
                     chaining_hints: true,
                     closure_return_type_hints: true,
-                    lifetime_elision_hints: LifetimeElisionHints::Never,
+                    lifetime_elision_hints: crate::LifetimeElisionHints::Never,
-                    reborrow_hints: false,
+                    reborrow_hints: crate::ReborrowHints::Never,
                     hide_named_constructor_hints: false,
                     param_names_for_lifetime_elision_hints: false,
                     max_length: Some(25),

crates/rust-analyzer/src/config.rs

@@ -12,8 +12,7 @@ use std::{ffi::OsString, fmt, iter, path::PathBuf};
 use flycheck::FlycheckConfig;
 use ide::{
     AssistConfig, CompletionConfig, DiagnosticsConfig, ExprFillDefaultMode, HighlightRelatedConfig,
-    HoverConfig, HoverDocFormat, InlayHintsConfig, JoinLinesConfig, LifetimeElisionHints, Snippet,
+    HoverConfig, HoverDocFormat, InlayHintsConfig, JoinLinesConfig, Snippet, SnippetScope,
-    SnippetScope,
 };
 use ide_db::{
     imports::insert_use::{ImportGranularity, InsertUseConfig, PrefixKind},
@@ -263,7 +262,7 @@ config_data! {
         /// site.
         inlayHints_parameterHints_enable: bool                     = "true",
         /// Whether to show inlay type hints for compiler inserted reborrows.
-        inlayHints_reborrowHints_enable: bool                      = "false",
+        inlayHints_reborrowHints_enable: ReborrowHintsDef          = "\"never\"",
         /// Whether to render leading colons for type hints, and trailing colons for parameter hints.
         inlayHints_renderColons: bool                              = "true",
         /// Whether to show inlay type hints for variables.
@@ -986,12 +985,16 @@ impl Config {
             chaining_hints: self.data.inlayHints_chainingHints_enable,
             closure_return_type_hints: self.data.inlayHints_closureReturnTypeHints_enable,
             lifetime_elision_hints: match self.data.inlayHints_lifetimeElisionHints_enable {
-                LifetimeElisionDef::Always => LifetimeElisionHints::Always,
+                LifetimeElisionDef::Always => ide::LifetimeElisionHints::Always,
-                LifetimeElisionDef::Never => LifetimeElisionHints::Never,
+                LifetimeElisionDef::Never => ide::LifetimeElisionHints::Never,
-                LifetimeElisionDef::SkipTrivial => LifetimeElisionHints::SkipTrivial,
+                LifetimeElisionDef::SkipTrivial => ide::LifetimeElisionHints::SkipTrivial,
             },
             hide_named_constructor_hints: self.data.inlayHints_typeHints_hideNamedConstructor,
-            reborrow_hints: self.data.inlayHints_reborrowHints_enable,
+            reborrow_hints: match self.data.inlayHints_reborrowHints_enable {
+                ReborrowHintsDef::Always => ide::ReborrowHints::Always,
+                ReborrowHintsDef::Never => ide::ReborrowHints::Never,
+                ReborrowHintsDef::Mutable => ide::ReborrowHints::MutableOnly,
+            },
             param_names_for_lifetime_elision_hints: self
                 .data
                 .inlayHints_lifetimeElisionHints_useParameterNames,
@@ -1293,6 +1296,7 @@ macro_rules! named_unit_variant {
 mod de_unit_v {
     named_unit_variant!(all);
     named_unit_variant!(skip_trivial);
+    named_unit_variant!(mutable);
 }
 
 #[derive(Deserialize, Debug, Clone, Copy)]
@@ -1404,6 +1408,17 @@ enum LifetimeElisionDef {
     SkipTrivial,
 }
 
+#[derive(Deserialize, Debug, Clone)]
+#[serde(untagged)]
+enum ReborrowHintsDef {
+    #[serde(deserialize_with = "true_or_always")]
+    Always,
+    #[serde(deserialize_with = "false_or_never")]
+    Never,
+    #[serde(deserialize_with = "de_unit_v::mutable")]
+    Mutable,
+}
+
 #[derive(Deserialize, Debug, Clone)]
 #[serde(rename_all = "snake_case")]
 enum ImportPrefixDef {
@@ -1675,6 +1690,15 @@ fn field_props(field: &str, ty: &str, doc: &[&str], default: &str) -> serde_json
                 "Only show lifetime elision hints if a return type is involved."
             ],
         },
+        "ReborrowHintsDef" => set! {
+            "type": ["string", "boolean"],
+            "enum": ["always", "never", "mutable"],
+            "enumDescriptions": [
+                "Always show reborrow hints.",
+                "Never show reborrow hints.",
+                "Only show mutable reborrow hints."
+            ],
+        },
         "CargoFeatures" => set! {
             "type": ["string", "array"],
             "items": { "type": "string" },

docs/user/generated_config.adoc

@@ -365,7 +365,7 @@ Maximum length for inlay hints. Set to null to have an unlimited length.
 Whether to show function parameter name inlay hints at the call
 site.
 --
-[[rust-analyzer.inlayHints.reborrowHints.enable]]rust-analyzer.inlayHints.reborrowHints.enable (default: `false`)::
+[[rust-analyzer.inlayHints.reborrowHints.enable]]rust-analyzer.inlayHints.reborrowHints.enable (default: `"never"`)::
 +
 --
 Whether to show inlay type hints for compiler inserted reborrows.

editors/code/package.json

@@ -810,8 +810,21 @@
                 },
                 "rust-analyzer.inlayHints.reborrowHints.enable": {
                     "markdownDescription": "Whether to show inlay type hints for compiler inserted reborrows.",
-                    "default": false,
+                    "default": "never",
-                    "type": "boolean"
+                    "type": [
+                        "string",
+                        "boolean"
+                    ],
+                    "enum": [
+                        "always",
+                        "never",
+                        "mutable"
+                    ],
+                    "enumDescriptions": [
+                        "Always show reborrow hints.",
+                        "Never show reborrow hints.",
+                        "Only show mutable reborrow hints."
+                    ]
                 },
                 "rust-analyzer.inlayHints.renderColons": {
                     "markdownDescription": "Whether to render leading colons for type hints, and trailing colons for parameter hints.",