format function

2 files changed, 169 insertions, 44 deletions

diff --git a/src/tools/rust-analyzer/crates/ide/src/inlay_hints/adjustment.rs b/src/tools/rust-analyzer/crates/ide/src/inlay_hints/adjustment.rs
index f2844a2eaa6..e3743daec49 100644
--- a/src/tools/rust-analyzer/crates/ide/src/inlay_hints/adjustment.rs
+++ b/src/tools/rust-analyzer/crates/ide/src/inlay_hints/adjustment.rs
@@ -109,50 +109,90 @@ pub(super) fn hints(
         }
         has_adjustments = true;
 
-        // FIXME: Add some nicer tooltips to each of these
-        let (text, coercion) = match kind {
+        let (text, coercion, detailed_tooltip) = match kind {
             Adjust::NeverToAny if config.adjustment_hints == AdjustmentHints::Always => {
                 allow_edit = false;
-                ("<never-to-any>", "never to any")
-            }
-            Adjust::Deref(None) => ("*", "dereference"),
-            Adjust::Deref(Some(OverloadedDeref(Mutability::Shared))) => {
-                ("*", "`Deref` dereference")
-            }
-            Adjust::Deref(Some(OverloadedDeref(Mutability::Mut))) => {
-                ("*", "`DerefMut` dereference")
-            }
-            Adjust::Borrow(AutoBorrow::Ref(Mutability::Shared)) => ("&", "borrow"),
-            Adjust::Borrow(AutoBorrow::Ref(Mutability::Mut)) => ("&mut ", "unique borrow"),
-            Adjust::Borrow(AutoBorrow::RawPtr(Mutability::Shared)) => {
-                ("&raw const ", "const pointer borrow")
-            }
-            Adjust::Borrow(AutoBorrow::RawPtr(Mutability::Mut)) => {
-                ("&raw mut ", "mut pointer borrow")
+                (
+                    "<never-to-any>",
+                    "never to any",
+                    "Coerces the never type `!` into any other type. This happens in code paths that never return, like after `panic!()` or `return`.",
+                )
             }
+            Adjust::Deref(None) => (
+                "*",
+                "dereference",
+                "Built-in dereference of a reference to access the underlying value. The compiler inserts `*` to get the value from `&T`.",
+            ),
+            Adjust::Deref(Some(OverloadedDeref(Mutability::Shared))) => (
+                "*",
+                "`Deref` dereference",
+                "Dereference via the `Deref` trait. Used for types like `Box<T>` or `Rc<T>` so they act like plain `T`.",
+            ),
+            Adjust::Deref(Some(OverloadedDeref(Mutability::Mut))) => (
+                "*",
+                "`DerefMut` dereference",
+                "Mutable dereference using the `DerefMut` trait. Enables smart pointers to give mutable access to their inner values.",
+            ),
+            Adjust::Borrow(AutoBorrow::Ref(Mutability::Shared)) => (
+                "&",
+                "shared borrow",
+                "Inserts `&` to create a shared reference. Lets you use a value without moving or cloning it.",
+            ),
+            Adjust::Borrow(AutoBorrow::Ref(Mutability::Mut)) => (
+                "&mut ",
+                "mutable borrow",
+                "Inserts `&mut` to create a unique, mutable reference. Lets you modify a value without taking ownership.",
+            ),
+            Adjust::Borrow(AutoBorrow::RawPtr(Mutability::Shared)) => (
+                "&raw const ",
+                "const raw pointer",
+                "Converts a reference to a raw const pointer `*const T`. Often used when working with FFI or unsafe code.",
+            ),
+            Adjust::Borrow(AutoBorrow::RawPtr(Mutability::Mut)) => (
+                "&raw mut ",
+                "mut raw pointer",
+                "Converts a mutable reference to a raw mutable pointer `*mut T`. Allows mutation in unsafe contexts.",
+            ),
             // some of these could be represented via `as` casts, but that's not too nice and
             // handling everything as a prefix expr makes the `(` and `)` insertion easier
             Adjust::Pointer(cast) if config.adjustment_hints == AdjustmentHints::Always => {
                 allow_edit = false;
                 match cast {
-                    PointerCast::ReifyFnPointer => {
-                        ("<fn-item-to-fn-pointer>", "fn item to fn pointer")
-                    }
+                    PointerCast::ReifyFnPointer => (
+                        "<fn-item-to-fn-pointer>",
+                        "fn item to fn pointer",
+                        "Converts a named function to a function pointer `fn()`. Useful when passing functions as values."
+                    ),
                     PointerCast::UnsafeFnPointer => (
                         "<safe-fn-pointer-to-unsafe-fn-pointer>",
                         "safe fn pointer to unsafe fn pointer",
+                        "Coerces a safe function pointer to an unsafe one. Allows calling it in an unsafe context."
+                    ),
+                    PointerCast::ClosureFnPointer(Safety::Unsafe) => (
+                        "<closure-to-unsafe-fn-pointer>",
+                        "closure to unsafe fn pointer",
+                        "Converts a non-capturing closure to an unsafe function pointer. Required for use in `extern` or unsafe APIs."
+                    ),
+                    PointerCast::ClosureFnPointer(Safety::Safe) => (
+                        "<closure-to-fn-pointer>",
+                        "closure to fn pointer",
+                        "Converts a non-capturing closure to a function pointer. Lets closures behave like plain functions."
+                    ),
+                    PointerCast::MutToConstPointer => (
+                        "<mut-ptr-to-const-ptr>",
+                        "mut ptr to const ptr",
+                        "Coerces `*mut T` to `*const T`. Safe because const pointers restrict what you can do."
+                    ),
+                    PointerCast::ArrayToPointer => (
+                        "<array-ptr-to-element-ptr>",
+                        "array to pointer",
+                        "Converts an array to a pointer to its first element. Similar to how arrays decay to pointers in C."
+                    ),
+                    PointerCast::Unsize => (
+                        "<unsize>",
+                        "unsize coercion",
+                        "Converts a sized type to an unsized one. Used for things like turning arrays into slices or concrete types into trait objects."
                     ),
-                    PointerCast::ClosureFnPointer(Safety::Unsafe) => {
-                        ("<closure-to-unsafe-fn-pointer>", "closure to unsafe fn pointer")
-                    }
-                    PointerCast::ClosureFnPointer(Safety::Safe) => {
-                        ("<closure-to-fn-pointer>", "closure to fn pointer")
-                    }
-                    PointerCast::MutToConstPointer => {
-                        ("<mut-ptr-to-const-ptr>", "mut ptr to const ptr")
-                    }
-                    PointerCast::ArrayToPointer => ("<array-ptr-to-element-ptr>", ""),
-                    PointerCast::Unsize => ("<unsize>", "unsize"),
                 }
             }
             _ => continue,
@@ -162,9 +202,12 @@ pub(super) fn hints(
             linked_location: None,
             tooltip: Some(config.lazy_tooltip(|| {
                 InlayTooltip::Markdown(format!(
-                    "`{}` → `{}` ({coercion} coercion)",
+                    "`{}` → `{}`\n\n**{}**\n\n{}",
                     source.display(sema.db, display_target),
                     target.display(sema.db, display_target),
+                    coercion.chars().next().unwrap().to_uppercase().collect::<String>()
+                        + &coercion[1..],
+                    detailed_tooltip
                 ))
             })),
         };
@@ -175,7 +218,7 @@ pub(super) fn hints(
     }
 
     if !postfix && needs_inner_parens {
-        pre.label.append_str("(");
+        (&mut pre.label).append_str("(");
     }
     if needs_outer_parens || (!postfix && needs_inner_parens) {
         post.label.append_str(")");
diff --git a/src/tools/rust-analyzer/crates/ide/src/inlay_hints/closing_brace.rs b/src/tools/rust-analyzer/crates/ide/src/inlay_hints/closing_brace.rs
index ca3a982760f..b2ee254701f 100644
--- a/src/tools/rust-analyzer/crates/ide/src/inlay_hints/closing_brace.rs
+++ b/src/tools/rust-analyzer/crates/ide/src/inlay_hints/closing_brace.rs
@@ -91,9 +91,9 @@ pub(super) fn hints(
         match_ast! {
             match parent {
                 ast::Fn(it) => {
-                    // FIXME: this could include parameters, but `HirDisplay` prints too much info
-                    // and doesn't respect the max length either, so the hints end up way too long
-                    (format!("fn {}", it.name()?), it.name().map(name))
+                    let hint_text = format_function_hint(&it, config.max_length?)
+                        .unwrap_or_else(|| format!("fn {}", it.name().map(|n| n.to_string()).unwrap_or_default()));
+                    (hint_text, it.name().map(name))
                 },
                 ast::Static(it) => (format!("static {}", it.name()?), it.name().map(name)),
                 ast::Const(it) => {
@@ -156,6 +156,47 @@ pub(super) fn hints(
     None
 }
 
+fn format_function_hint(func: &ast::Fn, max_length: usize) -> Option<String> {
+    let name = func.name()?;
+    let name_str = name.to_string();
+
+    let params = if let Some(param_list) = func.param_list() {
+        let mut param_parts = Vec::new();
+        let mut total_len = 0;
+        let max_param_len = max_length.saturating_sub(name_str.len() + 4);
+
+        for param in param_list.params() {
+            let param_text = if let Some(pat) = param.pat() {
+                if let Some(ty) = param.ty() { format!("{}: {}", pat, ty) } else { pat.to_string() }
+            } else if let Some(ty) = param.ty() {
+                format!("_: {}", ty)
+            } else {
+                let param_source = param.syntax().text().to_string();
+                if param_source.trim() == "..." { "...".to_string() } else { "_".to_string() }
+            };
+
+            let param_len = param_text.len() + if param_parts.is_empty() { 0 } else { 2 };
+            if total_len + param_len > max_param_len {
+                param_parts.push("...".to_string());
+                break;
+            }
+
+            total_len += param_len;
+            param_parts.push(param_text);
+        }
+
+        if param_parts.is_empty() {
+            "()".to_string()
+        } else {
+            format!("({})", param_parts.join(", "))
+        }
+    } else {
+        "()".to_string()
+    };
+
+    Some(format!("fn {}{}", name_str, params))
+}
+
 #[cfg(test)]
 mod tests {
     use crate::{
@@ -166,7 +207,11 @@ mod tests {
     #[test]
     fn hints_closing_brace() {
         check_with_config(
-            InlayHintsConfig { closing_brace_hints_min_lines: Some(2), ..DISABLED_CONFIG },
+            InlayHintsConfig {
+                closing_brace_hints_min_lines: Some(2),
+                max_length: Some(30),
+                ..DISABLED_CONFIG
+            },
             r#"
 fn a() {}
 
@@ -175,17 +220,17 @@ fn f() {
 
 fn g() {
   }
-//^ fn g
+//^ fn g()
 
 fn h<T>(with: T, arguments: u8, ...) {
   }
-//^ fn h
+//^ fn h(with: T, arguments: u8, ...)
 
 trait Tr {
     fn f();
     fn g() {
     }
-  //^ fn g
+  //^ fn g()
   }
 //^ trait Tr
 impl Tr for () {
@@ -222,7 +267,7 @@ fn f() {
     let v = vec![
     ];
   }
-//^ fn f
+//^ fn f()
 "#,
         );
     }
@@ -230,7 +275,11 @@ fn f() {
     #[test]
     fn hints_closing_brace_for_block_expr() {
         check_with_config(
-            InlayHintsConfig { closing_brace_hints_min_lines: Some(2), ..DISABLED_CONFIG },
+            InlayHintsConfig {
+                closing_brace_hints_min_lines: Some(2),
+                max_length: Some(10),
+                ..DISABLED_CONFIG
+            },
             r#"
 fn test() {
     'end: {
@@ -258,7 +307,40 @@ fn test() {
   //^ 'a
 
   }
-//^ fn test
+//^ fn test()
+"#,
+        );
+    }
+
+    #[test]
+    fn hints_closing_brace_function_parameters() {
+        check_with_config(
+            InlayHintsConfig {
+                closing_brace_hints_min_lines: Some(1),
+                max_length: Some(50),
+                ..DISABLED_CONFIG
+            },
+            r#"
+fn simple() {
+    let v = vec![
+    ];
+  }
+//^ fn simple()
+
+fn with_params(x: i32, y: String) {
+
+  }
+//^ fn with_params(x: i32, y: String)
+
+fn long_params(very_long_parameter_name: ComplexType, another: AnotherType) {
+
+  }
+//^ fn long_params(...)
+
+fn many_params(a: i32, b: i32, c: i32, d: i32, e: i32) {
+
+  }
+//^ fn many_params(a: i32, b: i32, c: i32, d: i32, ...)
 "#,
         );
     }