Merge rust-lang#11755

11755: feat: Implement lifetime elision hints r=Veykril a=Veykril

With names on:
![Code_erl26zKvuf](https://user-images.githubusercontent.com/3757771/159134856-e2c75d2d-f17c-45c7-9a78-3da5ee8b1acd.png)
With names off:
![Code_MRP1Pbfe9d](https://user-images.githubusercontent.com/3757771/159134857-30fac3a1-825e-4f49-ba9b-9fa0bb215694.png)


Co-authored-by: Lukas Wirth <lukastw97@gmail.com>

Author: bors[bot]

crates/ide/src/inlay_hints.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},
+    inlay_hints::{InlayHint, InlayHintsConfig, InlayKind, LifetimeElisionHints},
     join_lines::JoinLinesConfig,
     markup::Markup,
     moniker::{MonikerKind, MonikerResult, PackageInformation},

crates/ide/src/lib.rs

@@ -12,11 +12,14 @@ use ide_db::{
 use rustc_hash::FxHashSet;
 use syntax::{AstNode, SyntaxKind::*, SyntaxToken, TextRange, T};
 
-use crate::moniker::{crate_for_file, def_to_moniker, MonikerResult};
 use crate::{
     hover::hover_for_definition, Analysis, Fold, HoverConfig, HoverDocFormat, HoverResult,
     InlayHint, InlayHintsConfig, TryToNav,
 };
+use crate::{
+    moniker::{crate_for_file, def_to_moniker, MonikerResult},
+    LifetimeElisionHints,
+};
 
 /// A static representation of fully analyzed source code.
 ///
@@ -110,7 +113,9 @@ impl StaticIndex<'_> {
                     parameter_hints: true,
                     chaining_hints: true,
                     closure_return_type_hints: true,
+                    lifetime_elision_hints: LifetimeElisionHints::Never,
                     hide_named_constructor_hints: false,
+                    param_names_for_lifetime_elision_hints: false,
                     max_length: Some(25),
                 },
                 file_id,

crates/ide/src/static_index.rs

@@ -12,7 +12,8 @@ use std::{ffi::OsString, iter, path::PathBuf};
 use flycheck::FlycheckConfig;
 use ide::{
     AssistConfig, CompletionConfig, DiagnosticsConfig, ExprFillDefaultMode, HighlightRelatedConfig,
-    HoverConfig, HoverDocFormat, InlayHintsConfig, JoinLinesConfig, Snippet, SnippetScope,
+    HoverConfig, HoverDocFormat, InlayHintsConfig, JoinLinesConfig, LifetimeElisionHints, Snippet,
+    SnippetScope,
 };
 use ide_db::{
     imports::insert_use::{ImportGranularity, InsertUseConfig, PrefixKind},
@@ -243,20 +244,24 @@ config_data! {
         hoverActions_run: bool             = "true",
 
         /// Whether to render trailing colons for parameter hints, and trailing colons for parameter hints.
-        inlayHints_renderColons: bool               = "true",
+        inlayHints_renderColons: bool                      = "true",
         /// Maximum length for inlay hints. Set to null to have an unlimited length.
-        inlayHints_maxLength: Option<usize>         = "25",
+        inlayHints_maxLength: Option<usize>                = "25",
         /// Whether to show function parameter name inlay hints at the call
         /// site.
-        inlayHints_parameterHints: bool             = "true",
+        inlayHints_parameterHints: bool                     = "true",
         /// Whether to show inlay type hints for variables.
-        inlayHints_typeHints: bool                  = "true",
+        inlayHints_typeHints: bool                          = "true",
         /// Whether to show inlay type hints for method chains.
-        inlayHints_chainingHints: bool              = "true",
+        inlayHints_chainingHints: bool                      = "true",
         /// Whether to show inlay type hints for return types of closures with blocks.
-        inlayHints_closureReturnTypeHints: bool     = "false",
+        inlayHints_closureReturnTypeHints: bool             = "false",
+        /// Whether to show inlay type hints for elided lifetimes in function signatures.
+        inlayHints_lifetimeElisionHints: LifetimeElisionDef = "\"never\"",
+        /// Whether to prefer using parameter names as the name for elided lifetime hints if possible.
+        inlayHints_lifetimeElisionHints_useParameterNames: bool  = "false",
         /// Whether to hide inlay hints for constructors.
-        inlayHints_hideNamedConstructorHints: bool  = "false",
+        inlayHints_hideNamedConstructorHints: bool          = "false",
 
         /// Join lines inserts else between consecutive ifs.
         joinLines_joinElseIf: bool = "true",
@@ -855,7 +860,15 @@ impl Config {
             parameter_hints: self.data.inlayHints_parameterHints,
             chaining_hints: self.data.inlayHints_chainingHints,
             closure_return_type_hints: self.data.inlayHints_closureReturnTypeHints,
+            lifetime_elision_hints: match self.data.inlayHints_lifetimeElisionHints {
+                LifetimeElisionDef::Always => LifetimeElisionHints::Always,
+                LifetimeElisionDef::Never => LifetimeElisionHints::Never,
+                LifetimeElisionDef::SkipTrivial => LifetimeElisionHints::SkipTrivial,
+            },
             hide_named_constructor_hints: self.data.inlayHints_hideNamedConstructorHints,
+            param_names_for_lifetime_elision_hints: self
+                .data
+                .inlayHints_lifetimeElisionHints_useParameterNames,
             max_length: self.data.inlayHints_maxLength,
         }
     }
@@ -1125,6 +1138,16 @@ enum ImportGranularityDef {
     Module,
 }
 
+#[derive(Deserialize, Debug, Clone)]
+#[serde(rename_all = "snake_case")]
+enum LifetimeElisionDef {
+    #[serde(alias = "true")]
+    Always,
+    #[serde(alias = "false")]
+    Never,
+    SkipTrivial,
+}
+
 #[derive(Deserialize, Debug, Clone)]
 #[serde(rename_all = "snake_case")]
 enum ImportPrefixDef {
@@ -1377,7 +1400,16 @@ fn field_props(field: &str, ty: &str, doc: &[&str], default: &str) -> serde_json
             "minimum": 0,
             "maximum": 255
         },
-        _ => panic!("{}: {}", ty, default),
+        "LifetimeElisionDef" => set! {
+            "type": "string",
+            "enum": ["always", "never", "skip_trivial"],
+            "enumDescriptions": [
+                "Always show lifetime elision hints.",
+                "Never show lifetime elision hints.",
+                "Only show lifetime elision hints if a return type is involved."
+            ],
+        },
+        _ => panic!("missing entry for {}: {}", ty, default),
     }
 
     map.into()

crates/rust-analyzer/src/config.rs

@@ -427,27 +427,34 @@ pub(crate) fn inlay_hint(
         }),
         position: match inlay_hint.kind {
             InlayKind::ParameterHint => position(line_index, inlay_hint.range.start()),
-            InlayKind::ClosureReturnTypeHint | InlayKind::TypeHint | InlayKind::ChainingHint => {
-                position(line_index, inlay_hint.range.end())
-            }
+            InlayKind::ClosureReturnTypeHint
+            | InlayKind::TypeHint
+            | InlayKind::ChainingHint
+            | InlayKind::GenericParamListHint
+            | InlayKind::LifetimeHint => position(line_index, inlay_hint.range.end()),
         },
         kind: match inlay_hint.kind {
             InlayKind::ParameterHint => Some(lsp_ext::InlayHintKind::PARAMETER),
             InlayKind::ClosureReturnTypeHint | InlayKind::TypeHint | InlayKind::ChainingHint => {
                 Some(lsp_ext::InlayHintKind::TYPE)
             }
+            InlayKind::GenericParamListHint | InlayKind::LifetimeHint => None,
         },
         tooltip: None,
         padding_left: Some(match inlay_hint.kind {
             InlayKind::TypeHint => !render_colons,
             InlayKind::ParameterHint | InlayKind::ClosureReturnTypeHint => false,
             InlayKind::ChainingHint => true,
+            InlayKind::GenericParamListHint => false,
+            InlayKind::LifetimeHint => false,
         }),
         padding_right: Some(match inlay_hint.kind {
             InlayKind::TypeHint | InlayKind::ChainingHint | InlayKind::ClosureReturnTypeHint => {
                 false
             }
             InlayKind::ParameterHint => true,
+            InlayKind::LifetimeHint => true,
+            InlayKind::GenericParamListHint => false,
         }),
     }
 }

crates/rust-analyzer/src/to_proto.rs

@@ -306,15 +306,15 @@ fn extract_line_annotations(mut line: &str) -> Vec<LineAnnotation> {
         let end_marker = line_no_caret.find(|c| c == '$');
         let next = line_no_caret.find(marker).map_or(line.len(), |it| it + len);
 
-        let mut content = match end_marker {
-            Some(end_marker)
-                if end_marker < next
-                    && line_no_caret[end_marker..]
+        let cond = |end_marker| {
+            end_marker < next
+                && (line_no_caret[end_marker + 1..].is_empty()
+                    || line_no_caret[end_marker + 1..]
                         .strip_prefix(|c: char| c.is_whitespace() || c == '^')
-                        .is_some() =>
-            {
-                &line_no_caret[..end_marker]
-            }
+                        .is_some())
+        };
+        let mut content = match end_marker {
+            Some(end_marker) if cond(end_marker) => &line_no_caret[..end_marker],
             _ => line_no_caret[..next - len].trim_end(),
         };
 

crates/test_utils/src/lib.rs

@@ -378,6 +378,16 @@ Whether to show inlay type hints for method chains.
 --
 Whether to show inlay type hints for return types of closures with blocks.
 --
+[[rust-analyzer.inlayHints.lifetimeElisionHints]]rust-analyzer.inlayHints.lifetimeElisionHints (default: `"never"`)::
++
+--
+Whether to show inlay type hints for elided lifetimes in function signatures.
+--
+[[rust-analyzer.inlayHints.lifetimeElisionHints.useParameterNames]]rust-analyzer.inlayHints.lifetimeElisionHints.useParameterNames (default: `false`)::
++
+--
+Whether to prefer using parameter names as the name for elided lifetime hints if possible.
+--
 [[rust-analyzer.inlayHints.hideNamedConstructorHints]]rust-analyzer.inlayHints.hideNamedConstructorHints (default: `false`)::
 +
 --

docs/user/generated_config.adoc

@@ -795,6 +795,26 @@
                     "default": false,
                     "type": "boolean"
                 },
+                "rust-analyzer.inlayHints.lifetimeElisionHints": {
+                    "markdownDescription": "Whether to show inlay type hints for elided lifetimes in function signatures.",
+                    "default": "never",
+                    "type": "string",
+                    "enum": [
+                        "always",
+                        "never",
+                        "skip_trivial"
+                    ],
+                    "enumDescriptions": [
+                        "Always show lifetime elision hints.",
+                        "Never show lifetime elision hints.",
+                        "Only show lifetime elision hints if a return type is involved."
+                    ]
+                },
+                "rust-analyzer.inlayHints.lifetimeElisionHints.useParameterNames": {
+                    "markdownDescription": "Whether to prefer using parameter names as the name for elided lifetime hints if possible.",
+                    "default": false,
+                    "type": "boolean"
+                },
                 "rust-analyzer.inlayHints.hideNamedConstructorHints": {
                     "markdownDescription": "Whether to hide inlay hints for constructors.",
                     "default": false,