Use `ThinVec` in various AST types.

This commit changes the sequence parsers to produce `ThinVec`, which
triggers numerous conversions.

2 files changed, 7 insertions, 4 deletions

diff --git a/compiler/rustc_incremental/src/assert_module_sources.rs b/compiler/rustc_incremental/src/assert_module_sources.rs
index 2968a0e1203..b4b0ea00c50 100644
--- a/compiler/rustc_incremental/src/assert_module_sources.rs
+++ b/compiler/rustc_incremental/src/assert_module_sources.rs
@@ -30,6 +30,7 @@ use rustc_middle::mir::mono::CodegenUnitNameBuilder;
 use rustc_middle::ty::TyCtxt;
 use rustc_session::cgu_reuse_tracker::*;
 use rustc_span::symbol::{sym, Symbol};
+use thin_vec::ThinVec;
 
 #[allow(missing_docs)]
 pub fn assert_module_sources(tcx: TyCtxt<'_>) {
@@ -138,7 +139,7 @@ impl<'tcx> AssertModuleSource<'tcx> {
     }
 
     fn field(&self, attr: &ast::Attribute, name: Symbol) -> Symbol {
-        for item in attr.meta_item_list().unwrap_or_else(Vec::new) {
+        for item in attr.meta_item_list().unwrap_or_else(ThinVec::new) {
             if item.has_name(name) {
                 if let Some(value) = item.value_str() {
                     return value;
diff --git a/compiler/rustc_incremental/src/persist/dirty_clean.rs b/compiler/rustc_incremental/src/persist/dirty_clean.rs
index c6e63998c79..b839416c919 100644
--- a/compiler/rustc_incremental/src/persist/dirty_clean.rs
+++ b/compiler/rustc_incremental/src/persist/dirty_clean.rs
@@ -31,6 +31,8 @@ use rustc_middle::hir::nested_filter;
 use rustc_middle::ty::TyCtxt;
 use rustc_span::symbol::{sym, Symbol};
 use rustc_span::Span;
+use std::iter::FromIterator;
+use thin_vec::ThinVec;
 
 const LOADED_FROM_DISK: Symbol = sym::loaded_from_disk;
 const EXCEPT: Symbol = sym::except;
@@ -205,7 +207,7 @@ impl<'tcx> DirtyCleanVisitor<'tcx> {
 
     /// `loaded_from_disk=` attribute value
     fn loaded_from_disk(&self, attr: &Attribute) -> Labels {
-        for item in attr.meta_item_list().unwrap_or_else(Vec::new) {
+        for item in attr.meta_item_list().unwrap_or_else(ThinVec::new) {
             if item.has_name(LOADED_FROM_DISK) {
                 let value = expect_associated_value(self.tcx, &item);
                 return self.resolve_labels(&item, value);
@@ -217,7 +219,7 @@ impl<'tcx> DirtyCleanVisitor<'tcx> {
 
     /// `except=` attribute value
     fn except(&self, attr: &Attribute) -> Labels {
-        for item in attr.meta_item_list().unwrap_or_else(Vec::new) {
+        for item in attr.meta_item_list().unwrap_or_else(ThinVec::new) {
             if item.has_name(EXCEPT) {
                 let value = expect_associated_value(self.tcx, &item);
                 return self.resolve_labels(&item, value);
@@ -397,7 +399,7 @@ fn check_config(tcx: TyCtxt<'_>, attr: &Attribute) -> bool {
     let config = &tcx.sess.parse_sess.config;
     debug!("check_config: config={:?}", config);
     let mut cfg = None;
-    for item in attr.meta_item_list().unwrap_or_else(Vec::new) {
+    for item in attr.meta_item_list().unwrap_or_else(ThinVec::new) {
         if item.has_name(CFG) {
             let value = expect_associated_value(tcx, &item);
             debug!("check_config: searching for cfg {:?}", value);