Omit default parameter types

12 files changed, 150 insertions, 29 deletions

diff --git a/crates/ra_hir/src/lib.rs b/crates/ra_hir/src/lib.rs
index 2e52a1f5c..e9ca548ca 100644
--- a/crates/ra_hir/src/lib.rs
+++ b/crates/ra_hir/src/lib.rs
@@ -60,4 +60,7 @@ pub use hir_def::{
 pub use hir_expand::{
     name::Name, HirFileId, InFile, MacroCallId, MacroCallLoc, MacroDefId, MacroFile, Origin,
 };
-pub use hir_ty::{display::HirDisplay, CallableDef};
+pub use hir_ty::{
+    display::{HirDisplay, TruncateOptions},
+    CallableDef,
+};
diff --git a/crates/ra_hir_ty/src/display.rs b/crates/ra_hir_ty/src/display.rs
index 9bb3ece6c..9176c0629 100644
--- a/crates/ra_hir_ty/src/display.rs
+++ b/crates/ra_hir_ty/src/display.rs
@@ -9,7 +9,7 @@ pub struct HirFormatter<'a, 'b, DB> {
     fmt: &'a mut fmt::Formatter<'b>,
     buf: String,
     curr_size: usize,
-    max_size: Option<usize>,
+    truncate_options: Option<&'a TruncateOptions>,
 }
 
 pub trait HirDisplay {
@@ -25,12 +25,12 @@ pub trait HirDisplay {
     fn display_truncated<'a, DB>(
         &'a self,
         db: &'a DB,
-        max_size: Option<usize>,
+        truncate_options: &'a TruncateOptions,
     ) -> HirDisplayWrapper<'a, DB, Self>
     where
         Self: Sized,
     {
-        HirDisplayWrapper(db, self, max_size)
+        HirDisplayWrapper(db, self, Some(truncate_options))
     }
 }
 
@@ -66,15 +66,24 @@ where
     }
 
     pub fn should_truncate(&self) -> bool {
-        if let Some(max_size) = self.max_size {
+        if let Some(max_size) = self.truncate_options.and_then(|options| options.max_length) {
             self.curr_size >= max_size
         } else {
             false
         }
     }
+
+    pub fn should_display_default_types(&self) -> bool {
+        self.truncate_options.map(|options| options.show_default_types).unwrap_or(true)
+    }
+}
+
+pub struct TruncateOptions {
+    pub max_length: Option<usize>,
+    pub show_default_types: bool,
 }
 
-pub struct HirDisplayWrapper<'a, DB, T>(&'a DB, &'a T, Option<usize>);
+pub struct HirDisplayWrapper<'a, DB, T>(&'a DB, &'a T, Option<&'a TruncateOptions>);
 
 impl<'a, DB, T> fmt::Display for HirDisplayWrapper<'a, DB, T>
 where
@@ -87,7 +96,7 @@ where
             fmt: f,
             buf: String::with_capacity(20),
             curr_size: 0,
-            max_size: self.2,
+            truncate_options: self.2,
         })
     }
 }
diff --git a/crates/ra_hir_ty/src/lib.rs b/crates/ra_hir_ty/src/lib.rs
index 3ad913e55..7ca9e6b8a 100644
--- a/crates/ra_hir_ty/src/lib.rs
+++ b/crates/ra_hir_ty/src/lib.rs
@@ -906,7 +906,38 @@ impl HirDisplay for ApplicationTy {
                 write!(f, "{}", name)?;
                 if self.parameters.len() > 0 {
                     write!(f, "<")?;
-                    f.write_joined(&*self.parameters.0, ", ")?;
+
+                    let mut non_default_parameters = Vec::with_capacity(self.parameters.len());
+                    let parameters_to_write = if f.should_display_default_types() {
+                        self.parameters.0.as_ref()
+                    } else {
+                        match self
+                            .ctor
+                            .as_generic_def()
+                            .map(|generic_def_id| f.db.generic_defaults(generic_def_id))
+                            .filter(|defaults| !defaults.is_empty())
+                        {
+                            Option::None => self.parameters.0.as_ref(),
+                            Option::Some(default_parameters) => {
+                                for (i, parameter) in self.parameters.into_iter().enumerate() {
+                                    match (parameter, default_parameters.get(i)) {
+                                        (&Ty::Unknown, _) | (_, None) => {
+                                            non_default_parameters.push(parameter.clone())
+                                        }
+                                        (_, Some(default_parameter))
+                                            if parameter != default_parameter =>
+                                        {
+                                            non_default_parameters.push(parameter.clone())
+                                        }
+                                        _ => (),
+                                    }
+                                }
+                                &non_default_parameters
+                            }
+                        }
+                    };
+
+                    f.write_joined(parameters_to_write, ", ")?;
                     write!(f, ">")?;
                 }
             }
diff --git a/crates/ra_ide/src/inlay_hints.rs b/crates/ra_ide/src/inlay_hints.rs
index 3730121af..8674912a6 100644
--- a/crates/ra_ide/src/inlay_hints.rs
+++ b/crates/ra_ide/src/inlay_hints.rs
@@ -1,7 +1,7 @@
 //! FIXME: write short doc here
 
 use crate::{db::RootDatabase, FileId};
-use hir::{HirDisplay, SourceAnalyzer};
+use hir::{HirDisplay, SourceAnalyzer, TruncateOptions};
 use ra_syntax::{
     ast::{self, AstNode, TypeAscriptionOwner},
     match_ast, SmolStr, SourceFile, SyntaxKind, SyntaxNode, TextRange,
@@ -23,11 +23,11 @@ pub(crate) fn inlay_hints(
     db: &RootDatabase,
     file_id: FileId,
     file: &SourceFile,
-    max_inlay_hint_length: Option<usize>,
+    truncate_options: &TruncateOptions,
 ) -> Vec<InlayHint> {
     file.syntax()
         .descendants()
-        .map(|node| get_inlay_hints(db, file_id, &node, max_inlay_hint_length).unwrap_or_default())
+        .map(|node| get_inlay_hints(db, file_id, &node, truncate_options).unwrap_or_default())
         .flatten()
         .collect()
 }
@@ -36,7 +36,7 @@ fn get_inlay_hints(
     db: &RootDatabase,
     file_id: FileId,
     node: &SyntaxNode,
-    max_inlay_hint_length: Option<usize>,
+    truncate_options: &TruncateOptions,
 ) -> Option<Vec<InlayHint>> {
     let analyzer = SourceAnalyzer::new(db, hir::InFile::new(file_id.into(), node), None);
     match_ast! {
@@ -46,7 +46,7 @@ fn get_inlay_hints(
                     return None;
                 }
                 let pat = it.pat()?;
-                Some(get_pat_type_hints(db, &analyzer, pat, false, max_inlay_hint_length))
+                Some(get_pat_type_hints(db, &analyzer, pat, false, truncate_options))
             },
             ast::LambdaExpr(it) => {
                 it.param_list().map(|param_list| {
@@ -54,22 +54,22 @@ fn get_inlay_hints(
                         .params()
                         .filter(|closure_param| closure_param.ascribed_type().is_none())
                         .filter_map(|closure_param| closure_param.pat())
-                        .map(|root_pat| get_pat_type_hints(db, &analyzer, root_pat, false, max_inlay_hint_length))
+                        .map(|root_pat| get_pat_type_hints(db, &analyzer, root_pat, false, truncate_options))
                         .flatten()
                         .collect()
                 })
             },
             ast::ForExpr(it) => {
                 let pat = it.pat()?;
-                Some(get_pat_type_hints(db, &analyzer, pat, false, max_inlay_hint_length))
+                Some(get_pat_type_hints(db, &analyzer, pat, false, truncate_options))
             },
             ast::IfExpr(it) => {
                 let pat = it.condition()?.pat()?;
-                Some(get_pat_type_hints(db, &analyzer, pat, true, max_inlay_hint_length))
+                Some(get_pat_type_hints(db, &analyzer, pat, true, truncate_options))
             },
             ast::WhileExpr(it) => {
                 let pat = it.condition()?.pat()?;
-                Some(get_pat_type_hints(db, &analyzer, pat, true, max_inlay_hint_length))
+                Some(get_pat_type_hints(db, &analyzer, pat, true, truncate_options))
             },
             ast::MatchArmList(it) => {
                 Some(
@@ -77,7 +77,7 @@ fn get_inlay_hints(
                         .arms()
                         .map(|match_arm| match_arm.pats())
                         .flatten()
-                        .map(|root_pat| get_pat_type_hints(db, &analyzer, root_pat, true, max_inlay_hint_length))
+                        .map(|root_pat| get_pat_type_hints(db, &analyzer, root_pat, true, truncate_options))
                         .flatten()
                         .collect(),
                 )
@@ -92,7 +92,7 @@ fn get_pat_type_hints(
     analyzer: &SourceAnalyzer,
     root_pat: ast::Pat,
     skip_root_pat_hint: bool,
-    max_inlay_hint_length: Option<usize>,
+    truncate_options: &TruncateOptions,
 ) -> Vec<InlayHint> {
     let original_pat = &root_pat.clone();
 
@@ -109,7 +109,7 @@ fn get_pat_type_hints(
         .map(|(range, pat_type)| InlayHint {
             range,
             kind: InlayKind::TypeHint,
-            label: pat_type.display_truncated(db, max_inlay_hint_length).to_string().into(),
+            label: pat_type.display_truncated(db, truncate_options).to_string().into(),
         })
         .collect()
 }
@@ -160,6 +160,58 @@ mod tests {
     use crate::mock_analysis::single_file;
 
     #[test]
+    fn default_generic_types_disabled() {
+        let (analysis, file_id) = single_file(
+            r#"
+struct Test<K, T = u8> {
+k: K,
+    t: T,
+}
+
+fn main() {
+    let zz = Test { t: 23, k: 33 };
+}"#,
+        );
+
+        assert_debug_snapshot!(analysis.inlay_hints(file_id, None, false).unwrap(), @r###"
+        [
+            InlayHint {
+                range: [65; 67),
+                kind: TypeHint,
+                label: "Test<i32>",
+            },
+        ]
+        "###
+        );
+    }
+
+    #[test]
+    fn default_generic_types_enabled() {
+        let (analysis, file_id) = single_file(
+            r#"
+struct Test<K, T = u8> {
+    k: K,
+    t: T,
+}
+
+fn main() {
+    let zz = Test { t: 23, k: 33 };
+}"#,
+        );
+
+        assert_debug_snapshot!(analysis.inlay_hints(file_id, None, true).unwrap(), @r###"
+        [
+            InlayHint {
+                range: [69; 71),
+                kind: TypeHint,
+                label: "Test<i32, u8>",
+            },
+        ]
+        "###
+        );
+    }
+
+    #[test]
     fn let_statement() {
         let (analysis, file_id) = single_file(
             r#"
@@ -199,7 +251,7 @@ fn main() {
 }"#,
         );
 
-        assert_debug_snapshot!(analysis.inlay_hints(file_id, None).unwrap(), @r###"
+        assert_debug_snapshot!(analysis.inlay_hints(file_id, None, true).unwrap(), @r###"
         [
             InlayHint {
                 range: [193; 197),
@@ -273,7 +325,7 @@ fn main() {
 }"#,
         );
 
-        assert_debug_snapshot!(analysis.inlay_hints(file_id, None).unwrap(), @r###"
+        assert_debug_snapshot!(analysis.inlay_hints(file_id, None, true).unwrap(), @r###"
         [
             InlayHint {
                 range: [21; 30),
@@ -302,7 +354,7 @@ fn main() {
 }"#,
         );
 
-        assert_debug_snapshot!(analysis.inlay_hints(file_id, None).unwrap(), @r###"
+        assert_debug_snapshot!(analysis.inlay_hints(file_id, None, true).unwrap(), @r###"
         [
             InlayHint {
                 range: [21; 30),
@@ -350,7 +402,7 @@ fn main() {
 }"#,
         );
 
-        assert_debug_snapshot!(analysis.inlay_hints(file_id, None).unwrap(), @r###"
+        assert_debug_snapshot!(analysis.inlay_hints(file_id, None, true).unwrap(), @r###"
         [
             InlayHint {
                 range: [166; 170),
@@ -413,7 +465,7 @@ fn main() {
 }"#,
         );
 
-        assert_debug_snapshot!(analysis.inlay_hints(file_id, None).unwrap(), @r###"
+        assert_debug_snapshot!(analysis.inlay_hints(file_id, None, true).unwrap(), @r###"
         [
             InlayHint {
                 range: [166; 170),
@@ -476,7 +528,7 @@ fn main() {
 }"#,
         );
 
-        assert_debug_snapshot!(analysis.inlay_hints(file_id, None).unwrap(), @r###"
+        assert_debug_snapshot!(analysis.inlay_hints(file_id, None, true).unwrap(), @r###"
         [
             InlayHint {
                 range: [311; 315),
@@ -518,7 +570,7 @@ fn main() {
 }"#,
         );
 
-        assert_debug_snapshot!(analysis.inlay_hints(file_id, Some(8)).unwrap(), @r###"
+        assert_debug_snapshot!(analysis.inlay_hints(file_id, Some(8), true).unwrap(), @r###"
         [
             InlayHint {
                 range: [74; 75),
diff --git a/crates/ra_ide/src/lib.rs b/crates/ra_ide/src/lib.rs
index 779a81b2c..c3244a8dd 100644
--- a/crates/ra_ide/src/lib.rs
+++ b/crates/ra_ide/src/lib.rs
@@ -348,9 +348,14 @@ impl Analysis {
         &self,
         file_id: FileId,
         max_inlay_hint_length: Option<usize>,
+        show_default_types_in_inlay_hints: bool,
     ) -> Cancelable<Vec<InlayHint>> {
+        let truncate_options = hir::TruncateOptions {
+            max_length: max_inlay_hint_length,
+            show_default_types: show_default_types_in_inlay_hints,
+        };
         self.with_db(|db| {
-            inlay_hints::inlay_hints(db, file_id, &db.parse(file_id).tree(), max_inlay_hint_length)
+            inlay_hints::inlay_hints(db, file_id, &db.parse(file_id).tree(), &truncate_options)
         })
     }
 
diff --git a/crates/ra_lsp_server/src/config.rs b/crates/ra_lsp_server/src/config.rs
index 67942aa41..a916c5fd6 100644
--- a/crates/ra_lsp_server/src/config.rs
+++ b/crates/ra_lsp_server/src/config.rs
@@ -31,6 +31,7 @@ pub struct ServerConfig {
     pub lru_capacity: Option<usize>,
 
     pub max_inlay_hint_length: Option<usize>,
+    pub show_default_types_in_inlay_hints: bool,
 
     /// For internal usage to make integrated tests faster.
     #[serde(deserialize_with = "nullable_bool_true")]
@@ -51,6 +52,7 @@ impl Default for ServerConfig {
             use_client_watching: false,
             lru_capacity: None,
             max_inlay_hint_length: None,
+            show_default_types_in_inlay_hints: false,
             with_sysroot: true,
             feature_flags: FxHashMap::default(),
             cargo_features: Default::default(),
diff --git a/crates/ra_lsp_server/src/main_loop.rs b/crates/ra_lsp_server/src/main_loop.rs
index 965e7c53c..01fde3b2d 100644
--- a/crates/ra_lsp_server/src/main_loop.rs
+++ b/crates/ra_lsp_server/src/main_loop.rs
@@ -125,6 +125,7 @@ pub fn main_loop(
                     .and_then(|it| it.line_folding_only)
                     .unwrap_or(false),
                 max_inlay_hint_length: config.max_inlay_hint_length,
+                show_default_types_in_inlay_hints: config.show_default_types_in_inlay_hints,
             }
         };
 
diff --git a/crates/ra_lsp_server/src/main_loop/handlers.rs b/crates/ra_lsp_server/src/main_loop/handlers.rs
index 5b64b27cd..9069d1f1d 100644
--- a/crates/ra_lsp_server/src/main_loop/handlers.rs
+++ b/crates/ra_lsp_server/src/main_loop/handlers.rs
@@ -895,7 +895,11 @@ pub fn handle_inlay_hints(
     let analysis = world.analysis();
     let line_index = analysis.file_line_index(file_id)?;
     Ok(analysis
-        .inlay_hints(file_id, world.options.max_inlay_hint_length)?
+        .inlay_hints(
+            file_id,
+            world.options.max_inlay_hint_length,
+            world.options.show_default_types_in_inlay_hints,
+        )?
         .into_iter()
         .map(|api_type| InlayHint {
             label: api_type.label.to_string(),
diff --git a/crates/ra_lsp_server/src/world.rs b/crates/ra_lsp_server/src/world.rs
index 16cc11e8c..0b6eefcbc 100644
--- a/crates/ra_lsp_server/src/world.rs
+++ b/crates/ra_lsp_server/src/world.rs
@@ -31,6 +31,7 @@ pub struct Options {
     pub supports_location_link: bool,
     pub line_folding_only: bool,
     pub max_inlay_hint_length: Option<usize>,
+    pub show_default_types_in_inlay_hints: bool,
 }
 
 /// `WorldState` is the primary mutable state of the language server
diff --git a/editors/code/package.json b/editors/code/package.json
index f2e8e647e..bda0002b7 100644
--- a/editors/code/package.json
+++ b/editors/code/package.json
@@ -285,6 +285,11 @@
                     "default": 20,
                     "description": "Maximum length for inlay hints"
                 },
+                "rust-analyzer.showDefaultTypesInInlayHints": {
+                    "type": "boolean",
+                    "default": false,
+                    "description": "Display default types in inlay hints"
+                },
                 "rust-analyzer.cargoFeatures.noDefaultFeatures": {
                     "type": "boolean",
                     "default": false,
diff --git a/editors/code/src/config.ts b/editors/code/src/config.ts
index e131f09df..26bf30e7f 100644
--- a/editors/code/src/config.ts
+++ b/editors/code/src/config.ts
@@ -30,6 +30,7 @@ export class Config {
     public lruCapacity: null | number = null;
     public displayInlayHints = true;
     public maxInlayHintLength: null | number = null;
+    public showDefaultTypesInInlayHints = false;
     public excludeGlobs = [];
     public useClientWatching = true;
     public featureFlags = {};
@@ -153,6 +154,11 @@ export class Config {
                 'maxInlayHintLength',
             ) as number;
         }
+        if (config.has('showDefaultTypesInInlayHints')) {
+            this.showDefaultTypesInInlayHints = config.get(
+                'showDefaultTypesInInlayHints',
+            ) as boolean;
+        }
         if (config.has('excludeGlobs')) {
             this.excludeGlobs = config.get('excludeGlobs') || [];
         }
diff --git a/editors/code/src/server.ts b/editors/code/src/server.ts
index 5ace1d0fa..e7d1df943 100644
--- a/editors/code/src/server.ts
+++ b/editors/code/src/server.ts
@@ -55,6 +55,8 @@ export class Server {
                 publishDecorations: true,
                 lruCapacity: Server.config.lruCapacity,
                 maxInlayHintLength: Server.config.maxInlayHintLength,
+                showDefaultTypesInInlayHints:
+                    Server.config.showDefaultTypesInInlayHints,
                 excludeGlobs: Server.config.excludeGlobs,
                 useClientWatching: Server.config.useClientWatching,
                 featureFlags: Server.config.featureFlags,