Rust: replace singleton vectors with Option

rust/extractor/src/crate_graph.rs

@@ -346,12 +346,9 @@ fn emit_function(
     trap: &mut TrapFile,
     function: ra_ap_hir_def::FunctionId,
     visibility: Visibility,
-) -> Vec<trap::Label<generated::Item>> {
-    let mut items = Vec::new();
-    if let Some(type_) = db.value_ty(function.into()) {
-        items.push(const_or_function(db, name, trap, type_, visibility));
-    }
-    items
+) -> Option<trap::Label<generated::Item>> {
+    db.value_ty(function.into())
+        .map(|type_| const_or_function(db, name, trap, type_, visibility))
 }
 
 fn emit_const(
@@ -360,8 +357,7 @@ fn emit_const(
     trap: &mut TrapFile,
     konst: ra_ap_hir_def::ConstId,
     visibility: Visibility,
-) -> Vec<trap::Label<generated::Item>> {
-    let mut items = Vec::new();
+) -> Option<trap::Label<generated::Item>> {
     let type_ = db.value_ty(konst.into());
     let type_repr = type_.and_then(|type_| emit_hir_ty(trap, db, type_.skip_binders()));
     let name = Some(trap.emit(generated::Name {
@@ -370,7 +366,7 @@ fn emit_const(
     }));
     let konst = db.const_data(konst);
     let visibility = emit_visibility(db, trap, visibility);
-    items.push(
+    Some(
         trap.emit(generated::Const {
             id: trap::TrapId::Star,
             name,
@@ -382,8 +378,7 @@ fn emit_const(
             visibility,
         })
         .into(),
-    );
-    items
+    )
 }
 
 fn emit_static(
@@ -392,8 +387,7 @@ fn emit_static(
     trap: &mut TrapFile,
     statik: ra_ap_hir_def::StaticId,
     visibility: Visibility,
-) -> Vec<trap::Label<generated::Item>> {
-    let mut items = Vec::new();
+) -> Option<trap::Label<generated::Item>> {
     let type_ = db.value_ty(statik.into());
     let type_repr = type_.and_then(|type_| emit_hir_ty(trap, db, type_.skip_binders()));
     let name = Some(trap.emit(generated::Name {
@@ -402,7 +396,7 @@ fn emit_static(
     }));
     let statik = db.static_data(statik);
     let visibility = emit_visibility(db, trap, visibility);
-    items.push(
+    Some(
         trap.emit(generated::Static {
             id: trap::TrapId::Star,
             name,
@@ -415,8 +409,7 @@ fn emit_static(
             is_unsafe: statik.has_unsafe_kw(),
         })
         .into(),
-    );
-    items
+    )
 }
 
 fn emit_generic_param_list(
@@ -517,9 +510,7 @@ fn emit_adt(
     trap: &mut TrapFile,
     adt_id: ra_ap_hir_def::AdtId,
     visibility: Visibility,
-) -> Vec<trap::Label<generated::Item>> {
-    let mut items = Vec::new();
-
+) -> Option<trap::Label<generated::Item>> {
     match adt_id {
         ra_ap_hir_def::AdtId::StructId(struct_id) => {
             let name = Some(trap.emit(generated::Name {
@@ -529,7 +520,7 @@ fn emit_adt(
             let field_list = emit_variant_data(trap, db, struct_id.into()).into();
             let visibility = emit_visibility(db, trap, visibility);
             let generic_param_list = emit_generic_param_list(trap, db, adt_id.into());
-            items.push(
+            Some(
                 trap.emit(generated::Struct {
                     id: trap::TrapId::Star,
                     name,
@@ -540,7 +531,7 @@ fn emit_adt(
                     where_clause: None,
                 })
                 .into(),
-            );
+            )
         }
         ra_ap_hir_def::AdtId::EnumId(enum_id) => {
             let data = db.enum_variants(enum_id);
@@ -574,7 +565,7 @@ fn emit_adt(
             }));
             let visibility = emit_visibility(db, trap, visibility);
             let generic_param_list = emit_generic_param_list(trap, db, adt_id.into());
-            items.push(
+            Some(
                 trap.emit(generated::Enum {
                     id: trap::TrapId::Star,
                     name,
@@ -585,7 +576,7 @@ fn emit_adt(
                     where_clause: None,
                 })
                 .into(),
-            );
+            )
         }
         ra_ap_hir_def::AdtId::UnionId(union_id) => {
             let name = Some(trap.emit(generated::Name {
@@ -595,7 +586,7 @@ fn emit_adt(
             let struct_field_list = emit_variant_data(trap, db, union_id.into()).into();
             let visibility = emit_visibility(db, trap, visibility);
             let generic_param_list = emit_generic_param_list(trap, db, adt_id.into());
-            items.push(
+            Some(
                 trap.emit(generated::Union {
                     id: trap::TrapId::Star,
                     name,
@@ -606,10 +597,9 @@ fn emit_adt(
                     where_clause: None,
                 })
                 .into(),
-            );
+            )
         }
     }
-    items
 }
 
 fn emit_trait(
@@ -618,8 +608,7 @@ fn emit_trait(
     trap: &mut TrapFile,
     trait_id: ra_ap_hir_def::TraitId,
     visibility: Visibility,
-) -> Vec<trap::Label<generated::Item>> {
-    let mut items = Vec::new();
+) -> Option<trap::Label<generated::Item>> {
     let trait_items = db.trait_items(trait_id);
     let assoc_items: Vec<trap::Label<generated::AssocItem>> = trait_items
         .items
@@ -696,7 +685,7 @@ fn emit_trait(
     }));
     let visibility = emit_visibility(db, trap, visibility);
     let generic_param_list = emit_generic_param_list(trap, db, trait_id.into());
-    items.push(
+    Some(
         trap.emit(generated::Trait {
             id: trap::TrapId::Star,
             name,
@@ -710,8 +699,7 @@ fn emit_trait(
             where_clause: None,
         })
         .into(),
-    );
-    items
+    )
 }
 
 fn emit_module_impls(