feat: suggest name in let_stmt and fn_param

4 files changed, 37 insertions, 0 deletions

diff --git a/src/tools/rust-analyzer/crates/ide-completion/src/completions.rs b/src/tools/rust-analyzer/crates/ide-completion/src/completions.rs
index b537150608b..414627fbaba 100644
--- a/src/tools/rust-analyzer/crates/ide-completion/src/completions.rs
+++ b/src/tools/rust-analyzer/crates/ide-completion/src/completions.rs
@@ -617,6 +617,16 @@ impl Completions {
         }
         self.add_opt(render_struct_pat(RenderContext::new(ctx), pattern_ctx, strukt, local_name));
     }
+
+    pub(crate) fn suggest_name(&mut self, ctx: &CompletionContext<'_>, name: &str) {
+        let item = CompletionItem::new(
+            CompletionItemKind::Binding,
+            ctx.source_range(),
+            SmolStr::from(name),
+            ctx.edition,
+        );
+        item.add_to(self, ctx.db);
+    }
 }
 
 /// Calls the callback for each variant of the provided enum with the path to the variant.
diff --git a/src/tools/rust-analyzer/crates/ide-completion/src/completions/pattern.rs b/src/tools/rust-analyzer/crates/ide-completion/src/completions/pattern.rs
index 60cfb7e5a8c..2a06fc40175 100644
--- a/src/tools/rust-analyzer/crates/ide-completion/src/completions/pattern.rs
+++ b/src/tools/rust-analyzer/crates/ide-completion/src/completions/pattern.rs
@@ -1,6 +1,7 @@
 //! Completes constants and paths in unqualified patterns.
 
 use hir::{db::DefDatabase, AssocItem, ScopeDef};
+use ide_db::syntax_helpers::suggest_name;
 use syntax::ast::Pat;
 
 use crate::{
@@ -45,6 +46,18 @@ pub(crate) fn complete_pattern(
         return;
     }
 
+    // Suggest name only in let-stmt and fn param
+    if pattern_ctx.should_suggest_name {
+        if let Some(suggested) = ctx
+            .expected_type
+            .as_ref()
+            .map(|ty| ty.strip_references())
+            .and_then(|ty| suggest_name::for_type(&ty, ctx.db, ctx.edition))
+        {
+            acc.suggest_name(ctx, &suggested);
+        }
+    }
+
     let refutable = pattern_ctx.refutability == PatternRefutability::Refutable;
     let single_variant_enum = |enum_: hir::Enum| ctx.db.enum_data(enum_.into()).variants.len() == 1;
 
diff --git a/src/tools/rust-analyzer/crates/ide-completion/src/context.rs b/src/tools/rust-analyzer/crates/ide-completion/src/context.rs
index bcd9df94194..d457ba32bf0 100644
--- a/src/tools/rust-analyzer/crates/ide-completion/src/context.rs
+++ b/src/tools/rust-analyzer/crates/ide-completion/src/context.rs
@@ -264,6 +264,7 @@ pub(crate) struct PatternContext {
     pub(crate) refutability: PatternRefutability,
     pub(crate) param_ctx: Option<ParamContext>,
     pub(crate) has_type_ascription: bool,
+    pub(crate) should_suggest_name: bool,
     pub(crate) parent_pat: Option<ast::Pat>,
     pub(crate) ref_token: Option<SyntaxToken>,
     pub(crate) mut_token: Option<SyntaxToken>,
diff --git a/src/tools/rust-analyzer/crates/ide-completion/src/context/analysis.rs b/src/tools/rust-analyzer/crates/ide-completion/src/context/analysis.rs
index 292c419498d..1f9e3edf625 100644
--- a/src/tools/rust-analyzer/crates/ide-completion/src/context/analysis.rs
+++ b/src/tools/rust-analyzer/crates/ide-completion/src/context/analysis.rs
@@ -1430,10 +1430,23 @@ fn pattern_context_for(
         _ => (None, None),
     };
 
+    // Only suggest name in let-stmt or fn param
+    let should_suggest_name = matches!(
+            &pat,
+            ast::Pat::IdentPat(it)
+                if it.syntax()
+                .parent()
+                .map_or(false, |node| {
+                    let kind = node.kind();
+                    ast::LetStmt::can_cast(kind) || ast::Param::can_cast(kind)
+                })
+    );
+
     PatternContext {
         refutability,
         param_ctx,
         has_type_ascription,
+        should_suggest_name,
         parent_pat: pat.syntax().parent().and_then(ast::Pat::cast),
         mut_token,
         ref_token,