Use `ThinVec` in a few more AST types.

11 files changed, 72 insertions, 69 deletions

diff --git a/compiler/rustc_ast/src/ast.rs b/compiler/rustc_ast/src/ast.rs
index de6a0b563eb..03c375c4666 100644
--- a/compiler/rustc_ast/src/ast.rs
+++ b/compiler/rustc_ast/src/ast.rs
@@ -471,7 +471,7 @@ pub struct WhereEqPredicate {
 #[derive(Clone, Encodable, Decodable, Debug)]
 pub struct Crate {
     pub attrs: AttrVec,
-    pub items: Vec<P<Item>>,
+    pub items: ThinVec<P<Item>>,
     pub spans: ModSpans,
     /// Must be equal to `CRATE_NODE_ID` after the crate root is expanded, but may hold
     /// expansion placeholders or an unassigned value (`DUMMY_NODE_ID`) before that.
@@ -1357,7 +1357,7 @@ pub enum StructRest {
 pub struct StructExpr {
     pub qself: Option<P<QSelf>>,
     pub path: Path,
-    pub fields: Vec<ExprField>,
+    pub fields: ThinVec<ExprField>,
     pub rest: StructRest,
 }
 
@@ -2475,7 +2475,7 @@ pub enum ModKind {
     /// or with definition outlined to a separate file `mod foo;` and already loaded from it.
     /// The inner span is from the first token past `{` to the last token until `}`,
     /// or from the first to the last token in the loaded file.
-    Loaded(Vec<P<Item>>, Inline, ModSpans),
+    Loaded(ThinVec<P<Item>>, Inline, ModSpans),
     /// Module with definition outlined to a separate file `mod foo;` but not yet loaded from it.
     Unloaded,
 }
@@ -2502,7 +2502,7 @@ pub struct ForeignMod {
 
 #[derive(Clone, Encodable, Decodable, Debug)]
 pub struct EnumDef {
-    pub variants: Vec<Variant>,
+    pub variants: ThinVec<Variant>,
 }
 /// Enum variant.
 #[derive(Clone, Encodable, Decodable, Debug)]
@@ -3122,8 +3122,8 @@ mod size_asserts {
     static_assert_size!(GenericBound, 56);
     static_assert_size!(Generics, 40);
     static_assert_size!(Impl, 136);
-    static_assert_size!(Item, 144);
-    static_assert_size!(ItemKind, 72);
+    static_assert_size!(Item, 136);
+    static_assert_size!(ItemKind, 64);
     static_assert_size!(LitKind, 24);
     static_assert_size!(Local, 72);
     static_assert_size!(MetaItemLit, 40);
diff --git a/compiler/rustc_builtin_macros/src/deriving/clone.rs b/compiler/rustc_builtin_macros/src/deriving/clone.rs
index 3c1abe02036..dfee2d3ce77 100644
--- a/compiler/rustc_builtin_macros/src/deriving/clone.rs
+++ b/compiler/rustc_builtin_macros/src/deriving/clone.rs
@@ -200,7 +200,7 @@ fn cs_clone(
                     let call = subcall(cx, field);
                     cx.field_imm(field.span, ident, call)
                 })
-                .collect::<Vec<_>>();
+                .collect::<ThinVec<_>>();
 
             cx.expr_struct(trait_span, ctor_path, fields)
         }
diff --git a/compiler/rustc_builtin_macros/src/test.rs b/compiler/rustc_builtin_macros/src/test.rs
index 608d8c96668..e02c7e6c01b 100644
--- a/compiler/rustc_builtin_macros/src/test.rs
+++ b/compiler/rustc_builtin_macros/src/test.rs
@@ -249,14 +249,14 @@ pub fn expand_test_or_bench(
                 cx.expr_struct(
                     sp,
                     test_path("TestDescAndFn"),
-                    vec![
+                    thin_vec![
                         // desc: test::TestDesc {
                         field(
                             "desc",
                             cx.expr_struct(
                                 sp,
                                 test_path("TestDesc"),
-                                vec![
+                                thin_vec![
                                     // name: "path::to::test"
                                     field(
                                         "name",
diff --git a/compiler/rustc_expand/src/build.rs b/compiler/rustc_expand/src/build.rs
index eaecce91b8a..8a78c3296f9 100644
--- a/compiler/rustc_expand/src/build.rs
+++ b/compiler/rustc_expand/src/build.rs
@@ -323,7 +323,7 @@ impl<'a> ExtCtxt<'a> {
         &self,
         span: Span,
         path: ast::Path,
-        fields: Vec<ast::ExprField>,
+        fields: ThinVec<ast::ExprField>,
     ) -> P<ast::Expr> {
         self.expr(
             span,
@@ -339,7 +339,7 @@ impl<'a> ExtCtxt<'a> {
         &self,
         span: Span,
         id: Ident,
-        fields: Vec<ast::ExprField>,
+        fields: ThinVec<ast::ExprField>,
     ) -> P<ast::Expr> {
         self.expr_struct(span, self.path_ident(span, id), fields)
     }
diff --git a/compiler/rustc_expand/src/config.rs b/compiler/rustc_expand/src/config.rs
index 5c845ae6d0b..01500c2c77c 100644
--- a/compiler/rustc_expand/src/config.rs
+++ b/compiler/rustc_expand/src/config.rs
@@ -24,6 +24,7 @@ use rustc_session::Session;
 use rustc_span::edition::{Edition, ALL_EDITIONS};
 use rustc_span::symbol::{sym, Symbol};
 use rustc_span::{Span, DUMMY_SP};
+use thin_vec::ThinVec;
 
 /// A folder that strips out items that do not belong in the current configuration.
 pub struct StripUnconfigured<'a> {
@@ -206,7 +207,7 @@ pub fn features(
         None => {
             // The entire crate is unconfigured.
             krate.attrs = ast::AttrVec::new();
-            krate.items = Vec::new();
+            krate.items = ThinVec::new();
             Features::default()
         }
         Some(attrs) => {
diff --git a/compiler/rustc_expand/src/module.rs b/compiler/rustc_expand/src/module.rs
index 07f47a9c3a4..3779af19e12 100644
--- a/compiler/rustc_expand/src/module.rs
+++ b/compiler/rustc_expand/src/module.rs
@@ -12,8 +12,8 @@ use rustc_session::Session;
 use rustc_span::symbol::{sym, Ident};
 use rustc_span::Span;
 use std::iter::once;
-
 use std::path::{self, Path, PathBuf};
+use thin_vec::ThinVec;
 
 #[derive(Copy, Clone)]
 pub enum DirOwnership {
@@ -31,7 +31,7 @@ pub struct ModulePathSuccess {
 }
 
 pub(crate) struct ParsedExternalMod {
-    pub items: Vec<P<Item>>,
+    pub items: ThinVec<P<Item>>,
     pub spans: ModSpans,
     pub file_path: PathBuf,
     pub dir_path: PathBuf,
diff --git a/compiler/rustc_parse/src/parser/expr.rs b/compiler/rustc_parse/src/parser/expr.rs
index c92379754bf..12f65a436e3 100644
--- a/compiler/rustc_parse/src/parser/expr.rs
+++ b/compiler/rustc_parse/src/parser/expr.rs
@@ -2935,8 +2935,8 @@ impl<'a> Parser<'a> {
         pth: ast::Path,
         recover: bool,
         close_delim: Delimiter,
-    ) -> PResult<'a, (Vec<ExprField>, ast::StructRest, bool)> {
-        let mut fields = Vec::new();
+    ) -> PResult<'a, (ThinVec<ExprField>, ast::StructRest, bool)> {
+        let mut fields = ThinVec::new();
         let mut base = ast::StructRest::None;
         let mut recover_async = false;
 
diff --git a/compiler/rustc_parse/src/parser/item.rs b/compiler/rustc_parse/src/parser/item.rs
index 4e338f52f57..c0aed6a3789 100644
--- a/compiler/rustc_parse/src/parser/item.rs
+++ b/compiler/rustc_parse/src/parser/item.rs
@@ -56,12 +56,12 @@ impl<'a> Parser<'a> {
     pub fn parse_mod(
         &mut self,
         term: &TokenKind,
-    ) -> PResult<'a, (AttrVec, Vec<P<Item>>, ModSpans)> {
+    ) -> PResult<'a, (AttrVec, ThinVec<P<Item>>, ModSpans)> {
         let lo = self.token.span;
         let attrs = self.parse_inner_attributes()?;
 
         let post_attr_lo = self.token.span;
-        let mut items = vec![];
+        let mut items = ThinVec::new();
         while let Some(item) = self.parse_item(ForceCollect::No)? {
             items.push(item);
             self.maybe_consume_incorrect_semicolon(&items);
diff --git a/src/tools/rustfmt/src/modules.rs b/src/tools/rustfmt/src/modules.rs
index 7a0d1736c59..af9a154a6ae 100644
--- a/src/tools/rustfmt/src/modules.rs
+++ b/src/tools/rustfmt/src/modules.rs
@@ -6,6 +6,7 @@ use rustc_ast::ast;
 use rustc_ast::visit::Visitor;
 use rustc_span::symbol::{self, sym, Symbol};
 use rustc_span::Span;
+use thin_vec::ThinVec;
 use thiserror::Error;
 
 use crate::attr::MetaVisitor;
@@ -25,7 +26,7 @@ type FileModMap<'ast> = BTreeMap<FileName, Module<'ast>>;
 #[derive(Debug, Clone)]
 pub(crate) struct Module<'a> {
     ast_mod_kind: Option<Cow<'a, ast::ModKind>>,
-    pub(crate) items: Cow<'a, Vec<rustc_ast::ptr::P<ast::Item>>>,
+    pub(crate) items: Cow<'a, ThinVec<rustc_ast::ptr::P<ast::Item>>>,
     inner_attr: ast::AttrVec,
     pub(crate) span: Span,
 }
@@ -34,7 +35,7 @@ impl<'a> Module<'a> {
     pub(crate) fn new(
         mod_span: Span,
         ast_mod_kind: Option<Cow<'a, ast::ModKind>>,
-        mod_items: Cow<'a, Vec<rustc_ast::ptr::P<ast::Item>>>,
+        mod_items: Cow<'a, ThinVec<rustc_ast::ptr::P<ast::Item>>>,
         mod_attrs: Cow<'a, ast::AttrVec>,
     ) -> Self {
         let inner_attr = mod_attrs
@@ -157,7 +158,7 @@ impl<'ast, 'sess, 'c> ModResolver<'ast, 'sess> {
                     Module::new(
                         module_item.item.span,
                         Some(Cow::Owned(sub_mod_kind.clone())),
-                        Cow::Owned(vec![]),
+                        Cow::Owned(ThinVec::new()),
                         Cow::Owned(ast::AttrVec::new()),
                     ),
                 )?;
@@ -169,7 +170,7 @@ impl<'ast, 'sess, 'c> ModResolver<'ast, 'sess> {
     /// Visit modules defined inside macro calls.
     fn visit_mod_outside_ast(
         &mut self,
-        items: Vec<rustc_ast::ptr::P<ast::Item>>,
+        items: ThinVec<rustc_ast::ptr::P<ast::Item>>,
     ) -> Result<(), ModuleResolutionError> {
         for item in items {
             if is_cfg_if(&item) {
@@ -184,7 +185,7 @@ impl<'ast, 'sess, 'c> ModResolver<'ast, 'sess> {
                     Module::new(
                         span,
                         Some(Cow::Owned(sub_mod_kind.clone())),
-                        Cow::Owned(vec![]),
+                        Cow::Owned(ThinVec::new()),
                         Cow::Owned(ast::AttrVec::new()),
                     ),
                 )?;
@@ -210,7 +211,7 @@ impl<'ast, 'sess, 'c> ModResolver<'ast, 'sess> {
                     Module::new(
                         span,
                         Some(Cow::Borrowed(sub_mod_kind)),
-                        Cow::Owned(vec![]),
+                        Cow::Owned(ThinVec::new()),
                         Cow::Borrowed(&item.attrs),
                     ),
                 )?;
diff --git a/src/tools/rustfmt/src/parse/parser.rs b/src/tools/rustfmt/src/parse/parser.rs
index e0bd065518b..7ab042506bd 100644
--- a/src/tools/rustfmt/src/parse/parser.rs
+++ b/src/tools/rustfmt/src/parse/parser.rs
@@ -6,6 +6,7 @@ use rustc_ast::{ast, ptr};
 use rustc_errors::Diagnostic;
 use rustc_parse::{new_parser_from_file, parser::Parser as RawParser};
 use rustc_span::{sym, Span};
+use thin_vec::ThinVec;
 
 use crate::attr::first_attr_value_str_by_name;
 use crate::parse::session::ParseSess;
@@ -109,7 +110,7 @@ impl<'a> Parser<'a> {
         sess: &'a ParseSess,
         path: &Path,
         span: Span,
-    ) -> Result<(ast::AttrVec, Vec<ptr::P<ast::Item>>, Span), ParserError> {
+    ) -> Result<(ast::AttrVec, ThinVec<ptr::P<ast::Item>>, Span), ParserError> {
         let result = catch_unwind(AssertUnwindSafe(|| {
             let mut parser = new_parser_from_file(sess.inner(), path, Some(span));
             match parser.parse_mod(&TokenKind::Eof) {
diff --git a/tests/ui/stats/hir-stats.stderr b/tests/ui/stats/hir-stats.stderr
index 4e53070798f..ee62d8f2d25 100644
--- a/tests/ui/stats/hir-stats.stderr
+++ b/tests/ui/stats/hir-stats.stderr
@@ -3,67 +3,67 @@ ast-stats-1 Name                Accumulated Size         Count     Item Size
 ast-stats-1 ----------------------------------------------------------------
 ast-stats-1 GenericArgs               40 ( 0.6%)             1            40
 ast-stats-1 - AngleBracketed            40 ( 0.6%)             1
+ast-stats-1 Crate                     40 ( 0.6%)             1            40
 ast-stats-1 ExprField                 48 ( 0.7%)             1            48
-ast-stats-1 WherePredicate            56 ( 0.8%)             1            56
-ast-stats-1 - BoundPredicate            56 ( 0.8%)             1
-ast-stats-1 Crate                     56 ( 0.8%)             1            56
+ast-stats-1 WherePredicate            56 ( 0.9%)             1            56
+ast-stats-1 - BoundPredicate            56 ( 0.9%)             1
 ast-stats-1 Attribute                 64 ( 1.0%)             2            32
 ast-stats-1 - Normal                    32 ( 0.5%)             1
 ast-stats-1 - DocComment                32 ( 0.5%)             1
 ast-stats-1 Local                     72 ( 1.1%)             1            72
-ast-stats-1 Arm                       96 ( 1.4%)             2            48
-ast-stats-1 ForeignItem               96 ( 1.4%)             1            96
-ast-stats-1 - Fn                        96 ( 1.4%)             1
+ast-stats-1 Arm                       96 ( 1.5%)             2            48
+ast-stats-1 ForeignItem               96 ( 1.5%)             1            96
+ast-stats-1 - Fn                        96 ( 1.5%)             1
 ast-stats-1 FnDecl                   120 ( 1.8%)             5            24
 ast-stats-1 FieldDef                 160 ( 2.4%)             2            80
 ast-stats-1 Stmt                     160 ( 2.4%)             5            32
 ast-stats-1 - Local                     32 ( 0.5%)             1
 ast-stats-1 - MacCall                   32 ( 0.5%)             1
-ast-stats-1 - Expr                      96 ( 1.4%)             3
+ast-stats-1 - Expr                      96 ( 1.5%)             3
 ast-stats-1 Param                    160 ( 2.4%)             4            40
 ast-stats-1 Block                    192 ( 2.9%)             6            32
-ast-stats-1 Variant                  208 ( 3.1%)             2           104
+ast-stats-1 Variant                  208 ( 3.2%)             2           104
 ast-stats-1 GenericBound             224 ( 3.4%)             4            56
 ast-stats-1 - Trait                    224 ( 3.4%)             4
 ast-stats-1 AssocItem                416 ( 6.3%)             4           104
-ast-stats-1 - Type                     208 ( 3.1%)             2
-ast-stats-1 - Fn                       208 ( 3.1%)             2
-ast-stats-1 GenericParam             480 ( 7.2%)             5            96
-ast-stats-1 Pat                      504 ( 7.6%)             7            72
+ast-stats-1 - Type                     208 ( 3.2%)             2
+ast-stats-1 - Fn                       208 ( 3.2%)             2
+ast-stats-1 GenericParam             480 ( 7.3%)             5            96
+ast-stats-1 Pat                      504 ( 7.7%)             7            72
 ast-stats-1 - Struct                    72 ( 1.1%)             1
 ast-stats-1 - Wild                      72 ( 1.1%)             1
-ast-stats-1 - Ident                    360 ( 5.4%)             5
-ast-stats-1 Expr                     576 ( 8.7%)             8            72
+ast-stats-1 - Ident                    360 ( 5.5%)             5
+ast-stats-1 Expr                     576 ( 8.8%)             8            72
 ast-stats-1 - Path                      72 ( 1.1%)             1
 ast-stats-1 - Match                     72 ( 1.1%)             1
 ast-stats-1 - Struct                    72 ( 1.1%)             1
 ast-stats-1 - Lit                      144 ( 2.2%)             2
 ast-stats-1 - Block                    216 ( 3.3%)             3
-ast-stats-1 PathSegment              720 (10.8%)            30            24
-ast-stats-1 Ty                       896 (13.5%)            14            64
+ast-stats-1 PathSegment              720 (11.0%)            30            24
+ast-stats-1 Ty                       896 (13.7%)            14            64
 ast-stats-1 - Ptr                       64 ( 1.0%)             1
 ast-stats-1 - Ref                       64 ( 1.0%)             1
-ast-stats-1 - ImplicitSelf             128 ( 1.9%)             2
-ast-stats-1 - Path                     640 ( 9.6%)            10
-ast-stats-1 Item                   1_296 (19.5%)             9           144
-ast-stats-1 - Trait                    144 ( 2.2%)             1
-ast-stats-1 - Enum                     144 ( 2.2%)             1
-ast-stats-1 - ForeignMod               144 ( 2.2%)             1
-ast-stats-1 - Impl                     144 ( 2.2%)             1
-ast-stats-1 - Fn                       288 ( 4.3%)             2
-ast-stats-1 - Use                      432 ( 6.5%)             3
+ast-stats-1 - ImplicitSelf             128 ( 2.0%)             2
+ast-stats-1 - Path                     640 ( 9.8%)            10
+ast-stats-1 Item                   1_224 (18.7%)             9           136
+ast-stats-1 - Trait                    136 ( 2.1%)             1
+ast-stats-1 - Enum                     136 ( 2.1%)             1
+ast-stats-1 - ForeignMod               136 ( 2.1%)             1
+ast-stats-1 - Impl                     136 ( 2.1%)             1
+ast-stats-1 - Fn                       272 ( 4.2%)             2
+ast-stats-1 - Use                      408 ( 6.2%)             3
 ast-stats-1 ----------------------------------------------------------------
-ast-stats-1 Total                  6_640
+ast-stats-1 Total                  6_552
 ast-stats-1
 ast-stats-2 POST EXPANSION AST STATS
 ast-stats-2 Name                Accumulated Size         Count     Item Size
 ast-stats-2 ----------------------------------------------------------------
 ast-stats-2 GenericArgs               40 ( 0.6%)             1            40
 ast-stats-2 - AngleBracketed            40 ( 0.6%)             1
+ast-stats-2 Crate                     40 ( 0.6%)             1            40
 ast-stats-2 ExprField                 48 ( 0.7%)             1            48
 ast-stats-2 WherePredicate            56 ( 0.8%)             1            56
 ast-stats-2 - BoundPredicate            56 ( 0.8%)             1
-ast-stats-2 Crate                     56 ( 0.8%)             1            56
 ast-stats-2 Local                     72 ( 1.0%)             1            72
 ast-stats-2 Arm                       96 ( 1.3%)             2            48
 ast-stats-2 ForeignItem               96 ( 1.3%)             1            96
@@ -79,41 +79,41 @@ ast-stats-2 - Local                     32 ( 0.4%)             1
 ast-stats-2 - Semi                      32 ( 0.4%)             1
 ast-stats-2 - Expr                      96 ( 1.3%)             3
 ast-stats-2 Param                    160 ( 2.2%)             4            40
-ast-stats-2 Block                    192 ( 2.6%)             6            32
+ast-stats-2 Block                    192 ( 2.7%)             6            32
 ast-stats-2 Variant                  208 ( 2.9%)             2           104
 ast-stats-2 GenericBound             224 ( 3.1%)             4            56
 ast-stats-2 - Trait                    224 ( 3.1%)             4
-ast-stats-2 AssocItem                416 ( 5.7%)             4           104
+ast-stats-2 AssocItem                416 ( 5.8%)             4           104
 ast-stats-2 - Type                     208 ( 2.9%)             2
 ast-stats-2 - Fn                       208 ( 2.9%)             2
-ast-stats-2 GenericParam             480 ( 6.6%)             5            96
-ast-stats-2 Pat                      504 ( 6.9%)             7            72
+ast-stats-2 GenericParam             480 ( 6.7%)             5            96
+ast-stats-2 Pat                      504 ( 7.0%)             7            72
 ast-stats-2 - Struct                    72 ( 1.0%)             1
 ast-stats-2 - Wild                      72 ( 1.0%)             1
 ast-stats-2 - Ident                    360 ( 5.0%)             5
-ast-stats-2 Expr                     648 ( 8.9%)             9            72
+ast-stats-2 Expr                     648 ( 9.1%)             9            72
 ast-stats-2 - Path                      72 ( 1.0%)             1
 ast-stats-2 - Match                     72 ( 1.0%)             1
 ast-stats-2 - Struct                    72 ( 1.0%)             1
 ast-stats-2 - InlineAsm                 72 ( 1.0%)             1
 ast-stats-2 - Lit                      144 ( 2.0%)             2
 ast-stats-2 - Block                    216 ( 3.0%)             3
-ast-stats-2 PathSegment              792 (10.9%)            33            24
-ast-stats-2 Ty                       896 (12.3%)            14            64
+ast-stats-2 PathSegment              792 (11.1%)            33            24
+ast-stats-2 Ty                       896 (12.5%)            14            64
 ast-stats-2 - Ptr                       64 ( 0.9%)             1
 ast-stats-2 - Ref                       64 ( 0.9%)             1
 ast-stats-2 - ImplicitSelf             128 ( 1.8%)             2
-ast-stats-2 - Path                     640 ( 8.8%)            10
-ast-stats-2 Item                   1_584 (21.8%)            11           144
-ast-stats-2 - Trait                    144 ( 2.0%)             1
-ast-stats-2 - Enum                     144 ( 2.0%)             1
-ast-stats-2 - ExternCrate              144 ( 2.0%)             1
-ast-stats-2 - ForeignMod               144 ( 2.0%)             1
-ast-stats-2 - Impl                     144 ( 2.0%)             1
-ast-stats-2 - Fn                       288 ( 4.0%)             2
-ast-stats-2 - Use                      576 ( 7.9%)             4
+ast-stats-2 - Path                     640 ( 8.9%)            10
+ast-stats-2 Item                   1_496 (20.9%)            11           136
+ast-stats-2 - Trait                    136 ( 1.9%)             1
+ast-stats-2 - Enum                     136 ( 1.9%)             1
+ast-stats-2 - ExternCrate              136 ( 1.9%)             1
+ast-stats-2 - ForeignMod               136 ( 1.9%)             1
+ast-stats-2 - Impl                     136 ( 1.9%)             1
+ast-stats-2 - Fn                       272 ( 3.8%)             2
+ast-stats-2 - Use                      544 ( 7.6%)             4
 ast-stats-2 ----------------------------------------------------------------
-ast-stats-2 Total                  7_256
+ast-stats-2 Total                  7_152
 ast-stats-2
 hir-stats HIR STATS
 hir-stats Name                Accumulated Size         Count     Item Size