fix: add an option to show inlay hint for return type of closures without block

Author: harpsword

crates/ide/src/inlay_hints.rs

@@ -21,7 +21,7 @@ pub struct InlayHintsConfig {
     pub parameter_hints: bool,
     pub chaining_hints: bool,
     pub reborrow_hints: ReborrowHints,
-    pub closure_return_type_hints: bool,
+    pub closure_return_type_hints: ClosureReturnTypeHints,
     pub binding_mode_hints: bool,
     pub lifetime_elision_hints: LifetimeElisionHints,
     pub param_names_for_lifetime_elision_hints: bool,
@@ -31,6 +31,13 @@ pub struct InlayHintsConfig {
     pub closing_brace_hints_min_lines: Option<usize>,
 }
 
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum ClosureReturnTypeHints {
+    Always,
+    WithBlock,
+    Never,
+}
+
 #[derive(Clone, Debug, PartialEq, Eq)]
 pub enum LifetimeElisionHints {
     Always,
@@ -86,7 +93,7 @@ pub enum InlayTooltip {
 //
 // Optionally, one can enable additional hints for
 //
-// * return types of closure expressions with blocks
+// * return types of closure expressions
 // * elided lifetimes
 // * compiler inserted reborrows
 //
@@ -460,15 +467,17 @@ fn closure_ret_hints(
     file_id: FileId,
     closure: ast::ClosureExpr,
 ) -> Option<()> {
-    if !config.closure_return_type_hints {
+    if config.closure_return_type_hints == ClosureReturnTypeHints::Never {
         return None;
     }
 
     if closure.ret_type().is_some() {
         return None;
     }
 
-    if !closure_has_block_body(&closure) {
+    if !closure_has_block_body(&closure)
+        && config.closure_return_type_hints == ClosureReturnTypeHints::WithBlock
+    {
         return None;
     }
 
@@ -1092,13 +1101,15 @@ mod tests {
     use crate::inlay_hints::ReborrowHints;
     use crate::{fixture, inlay_hints::InlayHintsConfig, LifetimeElisionHints};
 
+    use super::ClosureReturnTypeHints;
+
     const DISABLED_CONFIG: InlayHintsConfig = InlayHintsConfig {
         render_colons: false,
         type_hints: false,
         parameter_hints: false,
         chaining_hints: false,
         lifetime_elision_hints: LifetimeElisionHints::Never,
-        closure_return_type_hints: false,
+        closure_return_type_hints: ClosureReturnTypeHints::Never,
         reborrow_hints: ReborrowHints::Always,
         binding_mode_hints: false,
         hide_named_constructor_hints: false,
@@ -1112,7 +1123,7 @@ mod tests {
         parameter_hints: true,
         chaining_hints: true,
         reborrow_hints: ReborrowHints::Always,
-        closure_return_type_hints: true,
+        closure_return_type_hints: ClosureReturnTypeHints::WithBlock,
         binding_mode_hints: true,
         lifetime_elision_hints: LifetimeElisionHints::Always,
         ..DISABLED_CONFIG
@@ -2054,6 +2065,23 @@ fn main() {
         );
     }
 
+    #[test]
+    fn return_type_hints_for_closure_without_block() {
+        check_with_config(
+            InlayHintsConfig {
+                closure_return_type_hints: ClosureReturnTypeHints::Always,
+                ..DISABLED_CONFIG
+            },
+            r#"
+fn main() {
+    let a = || { 0 };
+          //^^ i32
+    let b = || 0;
+          //^^ i32
+}"#,
+        );
+    }
+
     #[test]
     fn skip_closure_type_hints() {
         check_with_config(

crates/ide/src/lib.rs

@@ -81,7 +81,8 @@ pub use crate::{
     highlight_related::{HighlightRelatedConfig, HighlightedRange},
     hover::{HoverAction, HoverConfig, HoverDocFormat, HoverGotoTypeData, HoverResult},
     inlay_hints::{
-        InlayHint, InlayHintsConfig, InlayKind, InlayTooltip, LifetimeElisionHints, ReborrowHints,
+        ClosureReturnTypeHints, InlayHint, InlayHintsConfig, InlayKind, InlayTooltip,
+        LifetimeElisionHints, ReborrowHints,
     },
     join_lines::JoinLinesConfig,
     markup::Markup,

crates/ide/src/static_index.rs

@@ -109,7 +109,7 @@ impl StaticIndex<'_> {
                     type_hints: true,
                     parameter_hints: true,
                     chaining_hints: true,
-                    closure_return_type_hints: true,
+                    closure_return_type_hints: crate::ClosureReturnTypeHints::WithBlock,
                     lifetime_elision_hints: crate::LifetimeElisionHints::Never,
                     reborrow_hints: crate::ReborrowHints::Never,
                     hide_named_constructor_hints: false,

crates/rust-analyzer/src/config.rs

@@ -264,8 +264,8 @@ config_data! {
         /// Minimum number of lines required before the `}` until the hint is shown (set to 0 or 1
         /// to always show them).
         inlayHints_closingBraceHints_minLines: usize               = "25",
-        /// Whether to show inlay type hints for return types of closures with blocks.
-        inlayHints_closureReturnTypeHints_enable: bool             = "false",
+        /// Whether to show inlay type hints for return types of closures.
+        inlayHints_closureReturnTypeHints_enable: ClosureReturnTypeHintsDef  = "\"never\"",
         /// Whether to show inlay type hints for elided lifetimes in function signatures.
         inlayHints_lifetimeElisionHints_enable: LifetimeElisionDef = "\"never\"",
         /// Whether to prefer using parameter names as the name for elided lifetime hints if possible.
@@ -1014,7 +1014,11 @@ impl Config {
             type_hints: self.data.inlayHints_typeHints_enable,
             parameter_hints: self.data.inlayHints_parameterHints_enable,
             chaining_hints: self.data.inlayHints_chainingHints_enable,
-            closure_return_type_hints: self.data.inlayHints_closureReturnTypeHints_enable,
+            closure_return_type_hints: match self.data.inlayHints_closureReturnTypeHints_enable {
+                ClosureReturnTypeHintsDef::Always => ide::ClosureReturnTypeHints::Always,
+                ClosureReturnTypeHintsDef::Never => ide::ClosureReturnTypeHints::Never,
+                ClosureReturnTypeHintsDef::WithBlock => ide::ClosureReturnTypeHints::WithBlock,
+            },
             lifetime_elision_hints: match self.data.inlayHints_lifetimeElisionHints_enable {
                 LifetimeElisionDef::Always => ide::LifetimeElisionHints::Always,
                 LifetimeElisionDef::Never => ide::LifetimeElisionHints::Never,
@@ -1342,6 +1346,7 @@ mod de_unit_v {
     named_unit_variant!(all);
     named_unit_variant!(skip_trivial);
     named_unit_variant!(mutable);
+    named_unit_variant!(with_block);
 }
 
 #[derive(Deserialize, Debug, Clone, Copy)]
@@ -1454,6 +1459,17 @@ enum LifetimeElisionDef {
     SkipTrivial,
 }
 
+#[derive(Deserialize, Debug, Clone)]
+#[serde(untagged)]
+enum ClosureReturnTypeHintsDef {
+    #[serde(deserialize_with = "true_or_always")]
+    Always,
+    #[serde(deserialize_with = "false_or_never")]
+    Never,
+    #[serde(deserialize_with = "de_unit_v::with_block")]
+    WithBlock,
+}
+
 #[derive(Deserialize, Debug, Clone)]
 #[serde(untagged)]
 enum ReborrowHintsDef {
@@ -1740,6 +1756,19 @@ fn field_props(field: &str, ty: &str, doc: &[&str], default: &str) -> serde_json
                 "Only show lifetime elision hints if a return type is involved."
             ]
         },
+        "ClosureReturnTypeHintsDef" => set! {
+            "type": "string",
+            "enum": [
+                "always",
+                "never",
+                "with_block"
+            ],
+            "enumDescriptions": [
+                "Always show type hints for return types of closures.",
+                "Never show type hints for return types of closures.",
+                "Only show type hints for return types of closures with blocks."
+            ]
+        },
         "ReborrowHintsDef" => set! {
             "type": "string",
             "enum": [

docs/user/generated_config.adoc

@@ -366,10 +366,10 @@ Whether to show inlay hints after a closing `}` to indicate what item it belongs
 Minimum number of lines required before the `}` until the hint is shown (set to 0 or 1
 to always show them).
 --
-[[rust-analyzer.inlayHints.closureReturnTypeHints.enable]]rust-analyzer.inlayHints.closureReturnTypeHints.enable (default: `false`)::
+[[rust-analyzer.inlayHints.closureReturnTypeHints.enable]]rust-analyzer.inlayHints.closureReturnTypeHints.enable (default: `"never"`)::
 +
 --
-Whether to show inlay type hints for return types of closures with blocks.
+Whether to show inlay type hints for return types of closures.
 --
 [[rust-analyzer.inlayHints.lifetimeElisionHints.enable]]rust-analyzer.inlayHints.lifetimeElisionHints.enable (default: `"never"`)::
 +

editors/code/package.json

@@ -811,9 +811,19 @@
                     "minimum": 0
                 },
                 "rust-analyzer.inlayHints.closureReturnTypeHints.enable": {
-                    "markdownDescription": "Whether to show inlay type hints for return types of closures with blocks.",
-                    "default": false,
-                    "type": "boolean"
+                    "markdownDescription": "Whether to show inlay type hints for return types of closures.",
+                    "default": "never",
+                    "type": "string",
+                    "enum": [
+                        "always",
+                        "never",
+                        "with_block"
+                    ],
+                    "enumDescriptions": [
+                        "Always show type hints for return types of closures.",
+                        "Never show type hints for return types of closures.",
+                        "Only show type hints for return types of closures with blocks."
+                    ]
                 },
                 "rust-analyzer.inlayHints.lifetimeElisionHints.enable": {
                     "markdownDescription": "Whether to show inlay type hints for elided lifetimes in function signatures.",