Merge #3901

3901: Add more heuristics for hiding obvious param hints r=matklad a=IceSentry

This will now hide `value`, `pat`, `rhs` and `other`. These words were selected from the std because they are used in commonly used functions with only a single param and are obvious by their use.

It will also hide the hint if the passed param **starts** or end with the param_name. Maybe we could also split on '_' and check if one of the string is the param_name.

I think it would be good to also hide `bytes` if the type is `[u8; n]` but I'm not sure how to get the param type signature.

Closes #3900 



Co-authored-by: IceSentry <c.giguere42@gmail.com>

crates/ra_ide/src/inlay_hints.rs

@@ -1,4 +1,4 @@
-//! FIXME: write short doc here
+//! This module defines multiple types of inlay hints and their visibility
 
 use hir::{Adt, HirDisplay, Semantics, Type};
 use ra_ide_db::RootDatabase;
@@ -235,8 +235,7 @@ fn should_show_param_hint(
     param_name: &str,
     argument: &ast::Expr,
 ) -> bool {
-    let argument_string = argument.syntax().to_string();
-    if param_name.is_empty() || argument_string.ends_with(param_name) {
+    if param_name.is_empty() || is_argument_similar_to_param(argument, param_name) {
         return false;
     }
 
@@ -245,14 +244,37 @@ fn should_show_param_hint(
     } else {
         fn_signature.parameters.len()
     };
+
     // avoid displaying hints for common functions like map, filter, etc.
-    if parameters_len == 1 && (param_name.len() == 1 || param_name == "predicate") {
+    // or other obvious words used in std
+    if parameters_len == 1 && is_obvious_param(param_name) {
         return false;
     }
-
     true
 }
 
+fn is_argument_similar_to_param(argument: &ast::Expr, param_name: &str) -> bool {
+    let argument_string = remove_ref(argument.clone()).syntax().to_string();
+    argument_string.starts_with(&param_name) || argument_string.ends_with(&param_name)
+}
+
+fn remove_ref(expr: ast::Expr) -> ast::Expr {
+    if let ast::Expr::RefExpr(ref_expr) = &expr {
+        if let Some(inner) = ref_expr.expr() {
+            return inner;
+        }
+    }
+    expr
+}
+
+fn is_obvious_param(param_name: &str) -> bool {
+    let is_obvious_param_name = match param_name {
+        "predicate" | "value" | "pat" | "rhs" | "other" => true,
+        _ => false,
+    };
+    param_name.len() == 1 || is_obvious_param_name
+}
+
 fn get_fn_signature(sema: &Semantics<RootDatabase>, expr: &ast::Expr) -> Option<FunctionSignature> {
     match expr {
         ast::Expr::CallExpr(expr) => {
@@ -1059,9 +1081,18 @@ impl Test {
         self
     }
 
+    fn field(self, value: i32) -> Self {
+        self
+    }
+
     fn no_hints_expected(&self, _: i32, test_var: i32) {}
 }
 
+struct Param {}
+
+fn different_order(param: &Param) {}
+fn different_order_mut(param: &mut Param) {}
+
 fn main() {
     let container: TestVarContainer = TestVarContainer { test_var: 42 };
     let test: Test = Test {};
@@ -1069,11 +1100,20 @@ fn main() {
     map(22);
     filter(33);
 
-    let test_processed: Test = test.map(1).filter(2);
+    let test_processed: Test = test.map(1).filter(2).field(3);
 
     let test_var: i32 = 55;
     test_processed.no_hints_expected(22, test_var);
     test_processed.no_hints_expected(33, container.test_var);
+
+    let param_begin: Param = Param {};
+    different_order(&param_begin);
+    different_order(&mut param_begin);
+
+    let a: f64 = 7.0;
+    let b: f64 = 4.0;
+    let _: f64 = a.div_euclid(b);
+    let _: f64 = a.abs_sub(b);
 }"#,
         );