feat: add config for inserting must_use in generate_enum_as_method

crates/ide-assists/src/assist_config.rs

@@ -14,4 +14,5 @@ pub struct AssistConfig {
     pub allowed: Option<Vec<AssistKind>>,
     pub insert_use: InsertUseConfig,
     pub prefer_no_std: bool,
+    pub assist_emit_must_use: bool,
 }

crates/ide-assists/src/handlers/generate_enum_projection_method.rs

@@ -124,6 +124,7 @@ fn generate_enum_projection_method(
         happy_case,
         sad_case,
     } = props;
+
     let variant = ctx.find_node_at_offset::<ast::Variant>()?;
     let variant_name = variant.name()?;
     let parent_enum = ast::Adt::Enum(variant.parent_enum());
@@ -144,7 +145,7 @@ fn generate_enum_projection_method(
         ast::StructKind::Unit => return None,
     };
 
-    let fn_name = format!("{}_{}", fn_name_prefix, &to_lower_snake_case(&variant_name.text()));
+    let fn_name = format!("{fn_name_prefix}_{}", &to_lower_snake_case(&variant_name.text()));
 
     // Return early if we've found an existing new fn
     let impl_def = find_struct_impl(ctx, &parent_enum, &fn_name)?;
@@ -156,15 +157,31 @@ fn generate_enum_projection_method(
         assist_description,
         target,
         |builder| {
-            let vis = parent_enum.visibility().map_or(String::new(), |v| format!("{v} "));
-            let method = format!(
-                "    {vis}fn {fn_name}({self_param}) -> {return_prefix}{field_type}{return_suffix} {{
+            let vis = parent_enum.visibility().map_or(String::new(), |v| format!("{} ", v));
+
+            let field_type_syntax = field_type.syntax();
+
+            let method = if ctx.config.assist_emit_must_use
+            {
+                format!(
+                    "    #[must_use]
+    {vis}fn {fn_name}({self_param}) -> {return_prefix}{field_type_syntax}{return_suffix} {{
         if let Self::{variant_name}{pattern_suffix} = self {{
             {happy_case}({bound_name})
         }} else {{
             {sad_case}
         }}
-    }}");
+    }}")
+            } else {
+                format!(
+                    "    {vis}fn {fn_name}({self_param}) -> {return_prefix}{field_type_syntax}{return_suffix} {{
+        if let Self::{variant_name}{pattern_suffix} = self {{
+            {happy_case}({bound_name})
+        }} else {{
+            {sad_case}
+        }}
+    }}")
+            };
 
             add_method_to_adt(builder, &parent_enum, impl_def, &method);
         },

crates/ide-assists/src/tests.rs

@@ -30,6 +30,7 @@ pub(crate) const TEST_CONFIG: AssistConfig = AssistConfig {
         skip_glob_imports: true,
     },
     prefer_no_std: false,
+    assist_emit_must_use: false,
 };
 
 pub(crate) fn with_single_file(text: &str) -> (RootDatabase, FileId) {

crates/rust-analyzer/src/config.rs

@@ -56,6 +56,9 @@ mod patch_old_style;
 // parsing the old name.
 config_data! {
     struct ConfigData {
+        /// Whether to insert must_use derive macro while generating `as_` methods
+        /// for enum variants.
+        assist_emitMustUse: bool               = "false",
         /// Placeholder expression to use for missing expressions in assists.
         assist_expressionFillDefault: ExprFillDefaultDef              = "\"todo\"",
 
@@ -1227,6 +1230,7 @@ impl Config {
             allowed: None,
             insert_use: self.insert_use_config(),
             prefer_no_std: self.data.imports_prefer_no_std,
+            assist_emit_must_use: self.data.assist_emitMustUse,
         }
     }
 

docs/user/generated_config.adoc

@@ -1,3 +1,9 @@
+[[rust-analyzer.assist.emitMustUse]]rust-analyzer.assist.emitMustUse (default: `false`)::
++
+--
+Whether to insert must_use derive macro while generating `as_` methods
+for enum variants.
+--
 [[rust-analyzer.assist.expressionFillDefault]]rust-analyzer.assist.expressionFillDefault (default: `"todo"`)::
 +
 --

editors/code/package.json

@@ -397,6 +397,11 @@
                     "type": "boolean"
                 },
                 "$generated-start": {},
+                "rust-analyzer.assist.emitMustUse": {
+                    "markdownDescription": "Whether to insert must_use derive macro while generating `as_` methods\nfor enum variants.",
+                    "default": false,
+                    "type": "boolean"
+                },
                 "rust-analyzer.assist.expressionFillDefault": {
                     "markdownDescription": "Placeholder expression to use for missing expressions in assists.",
                     "default": "todo",