Merge #1549

1549: Show type lenses for the resolved let bindings r=matklad a=SomeoneToIgnore

Types that are fully unresolved are not displayed:

<img width="279" alt="image" src="https://user-images.githubusercontent.com/2690773/61518122-8e4ba980-aa11-11e9-9249-6d9f9b202e6a.png">

A few concerns that I have about the current implementation:

* I've adjusted the `file_structure` API method to return the information about the `let` bindings.
Although it works fine, I have a feeling that adding a new API method would be the better way.
But this requires some prior discussion, so I've decided to go for an easy way with an MVP. 
Would be nice to hear your suggestions.

* There's a hardcoded `{undersolved}` check that I was forced to use, since the method that resolves types returns a `String`. 
Is there a better typed API I can use? This will help, for instance, to add an action to the type lenses that will allow us to navigate to the type.

Co-authored-by: Kirill Bulatov <[email protected]>

3 files changed, 50 insertions, 1 deletions

diff --git a/crates/ra_lsp_server/src/main_loop.rs b/crates/ra_lsp_server/src/main_loop.rs
index 668d2fd72..8e830c8b8 100644
--- a/crates/ra_lsp_server/src/main_loop.rs
+++ b/crates/ra_lsp_server/src/main_loop.rs
@@ -362,6 +362,7 @@ fn on_request(
         .on::<req::References>(handlers::handle_references)?
         .on::<req::Formatting>(handlers::handle_formatting)?
         .on::<req::DocumentHighlightRequest>(handlers::handle_document_highlight)?
+        .on::<req::InlayHints>(handlers::handle_inlay_hints)?
         .finish();
     Ok(())
 }
diff --git a/crates/ra_lsp_server/src/main_loop/handlers.rs b/crates/ra_lsp_server/src/main_loop/handlers.rs
index 68865b755..5bf950a53 100644
--- a/crates/ra_lsp_server/src/main_loop/handlers.rs
+++ b/crates/ra_lsp_server/src/main_loop/handlers.rs
@@ -21,7 +21,7 @@ use url_serde::Ser;
 use crate::{
     cargo_target_spec::{runnable_args, CargoTargetSpec},
     conv::{to_location, Conv, ConvWith, MapConvWith, TryConvWith, TryConvWithToVec},
-    req::{self, Decoration},
+    req::{self, Decoration, InlayHint, InlayHintsParams, InlayKind},
     world::WorldSnapshot,
     LspError, Result,
 };
@@ -874,3 +874,24 @@ fn to_diagnostic_severity(severity: Severity) -> DiagnosticSeverity {
         WeakWarning => DiagnosticSeverity::Hint,
     }
 }
+
+pub fn handle_inlay_hints(
+    world: WorldSnapshot,
+    params: InlayHintsParams,
+) -> Result<Vec<InlayHint>> {
+    let file_id = params.text_document.try_conv_with(&world)?;
+    let analysis = world.analysis();
+    let line_index = analysis.file_line_index(file_id);
+    Ok(analysis
+        .inlay_hints(file_id)?
+        .into_iter()
+        .map(|api_type| InlayHint {
+            label: api_type.label.to_string(),
+            range: api_type.range.conv_with(&line_index),
+            kind: match api_type.kind {
+                ra_ide_api::InlayKind::LetBindingType => InlayKind::LetBindingType,
+                ra_ide_api::InlayKind::ClosureParameterType => InlayKind::ClosureParameterType,
+            },
+        })
+        .collect())
+}
diff --git a/crates/ra_lsp_server/src/req.rs b/crates/ra_lsp_server/src/req.rs
index 8d39b04a7..916185f99 100644
--- a/crates/ra_lsp_server/src/req.rs
+++ b/crates/ra_lsp_server/src/req.rs
@@ -196,3 +196,30 @@ pub struct SourceChange {
     pub workspace_edit: WorkspaceEdit,
     pub cursor_position: Option<TextDocumentPositionParams>,
 }
+
+pub enum InlayHints {}
+
+impl Request for InlayHints {
+    type Params = InlayHintsParams;
+    type Result = Vec<InlayHint>;
+    const METHOD: &'static str = "rust-analyzer/inlayHints";
+}
+
+#[derive(Serialize, Deserialize, Debug)]
+#[serde(rename_all = "camelCase")]
+pub struct InlayHintsParams {
+    pub text_document: TextDocumentIdentifier,
+}
+
+#[derive(Debug, PartialEq, Eq, Deserialize, Serialize)]
+pub enum InlayKind {
+    LetBindingType,
+    ClosureParameterType,
+}
+
+#[derive(Debug, Deserialize, Serialize)]
+pub struct InlayHint {
+    pub range: Range,
+    pub kind: InlayKind,
+    pub label: String,
+}