Use `ThinVec` in `ast::WhereClause`.

6 files changed, 92 insertions, 76 deletions

diff --git a/compiler/rustc_ast/src/ast.rs b/compiler/rustc_ast/src/ast.rs
index 815e00228fa..9ed451f13b2 100644
--- a/compiler/rustc_ast/src/ast.rs
+++ b/compiler/rustc_ast/src/ast.rs
@@ -403,13 +403,13 @@ pub struct WhereClause {
     /// if we parsed no predicates (e.g. `struct Foo where {}`).
     /// This allows us to pretty-print accurately.
     pub has_where_token: bool,
-    pub predicates: Vec<WherePredicate>,
+    pub predicates: ThinVec<WherePredicate>,
     pub span: Span,
 }
 
 impl Default for WhereClause {
     fn default() -> WhereClause {
-        WhereClause { has_where_token: false, predicates: Vec::new(), span: DUMMY_SP }
+        WhereClause { has_where_token: false, predicates: ThinVec::new(), span: DUMMY_SP }
     }
 }
 
@@ -3115,15 +3115,15 @@ mod size_asserts {
     static_assert_size!(Block, 48);
     static_assert_size!(Expr, 72);
     static_assert_size!(ExprKind, 40);
-    static_assert_size!(Fn, 168);
+    static_assert_size!(Fn, 152);
     static_assert_size!(ForeignItem, 96);
     static_assert_size!(ForeignItemKind, 24);
     static_assert_size!(GenericArg, 24);
     static_assert_size!(GenericBound, 56);
-    static_assert_size!(Generics, 56);
-    static_assert_size!(Impl, 168);
-    static_assert_size!(Item, 168);
-    static_assert_size!(ItemKind, 96);
+    static_assert_size!(Generics, 40);
+    static_assert_size!(Impl, 152);
+    static_assert_size!(Item, 152);
+    static_assert_size!(ItemKind, 80);
     static_assert_size!(LitKind, 24);
     static_assert_size!(Local, 72);
     static_assert_size!(MetaItemLit, 40);
diff --git a/compiler/rustc_ast/src/mut_visit.rs b/compiler/rustc_ast/src/mut_visit.rs
index 6eb788a3f82..a22e8638f73 100644
--- a/compiler/rustc_ast/src/mut_visit.rs
+++ b/compiler/rustc_ast/src/mut_visit.rs
@@ -17,10 +17,10 @@ use rustc_data_structures::sync::Lrc;
 use rustc_span::source_map::Spanned;
 use rustc_span::symbol::Ident;
 use rustc_span::Span;
-
 use smallvec::{smallvec, Array, SmallVec};
 use std::ops::DerefMut;
 use std::{panic, ptr};
+use thin_vec::ThinVec;
 
 pub trait ExpectOne<A: Array> {
     fn expect_one(self, err: &'static str) -> A::Item;
@@ -337,6 +337,17 @@ where
 
 // No `noop_` prefix because there isn't a corresponding method in `MutVisitor`.
 #[inline]
+pub fn visit_thin_vec<T, F>(elems: &mut ThinVec<T>, mut visit_elem: F)
+where
+    F: FnMut(&mut T),
+{
+    for elem in elems {
+        visit_elem(elem);
+    }
+}
+
+// No `noop_` prefix because there isn't a corresponding method in `MutVisitor`.
+#[inline]
 pub fn visit_opt<T, F>(opt: &mut Option<T>, mut visit_elem: F)
 where
     F: FnMut(&mut T),
@@ -917,7 +928,7 @@ pub fn noop_visit_generics<T: MutVisitor>(generics: &mut Generics, vis: &mut T)
 
 pub fn noop_visit_where_clause<T: MutVisitor>(wc: &mut WhereClause, vis: &mut T) {
     let WhereClause { has_where_token: _, predicates, span } = wc;
-    visit_vec(predicates, |predicate| vis.visit_where_predicate(predicate));
+    visit_thin_vec(predicates, |predicate| vis.visit_where_predicate(predicate));
     vis.visit_span(span);
 }
 
diff --git a/compiler/rustc_ast_pretty/src/pprust/state.rs b/compiler/rustc_ast_pretty/src/pprust/state.rs
index 5eac3c47a46..694d688bf1f 100644
--- a/compiler/rustc_ast_pretty/src/pprust/state.rs
+++ b/compiler/rustc_ast_pretty/src/pprust/state.rs
@@ -1724,7 +1724,7 @@ impl<'a> State<'a> {
             params: ThinVec::new(),
             where_clause: ast::WhereClause {
                 has_where_token: false,
-                predicates: Vec::new(),
+                predicates: ThinVec::new(),
                 span: DUMMY_SP,
             },
             span: DUMMY_SP,
diff --git a/compiler/rustc_builtin_macros/src/deriving/generic/ty.rs b/compiler/rustc_builtin_macros/src/deriving/generic/ty.rs
index aabd5b1f773..8314d59d845 100644
--- a/compiler/rustc_builtin_macros/src/deriving/generic/ty.rs
+++ b/compiler/rustc_builtin_macros/src/deriving/generic/ty.rs
@@ -9,6 +9,7 @@ use rustc_expand::base::ExtCtxt;
 use rustc_span::source_map::{respan, DUMMY_SP};
 use rustc_span::symbol::{kw, Ident, Symbol};
 use rustc_span::Span;
+use thin_vec::ThinVec;
 
 /// A path, e.g., `::std::option::Option::<i32>` (global). Has support
 /// for type parameters.
@@ -185,7 +186,11 @@ impl Bounds {
 
         Generics {
             params,
-            where_clause: ast::WhereClause { has_where_token: false, predicates: Vec::new(), span },
+            where_clause: ast::WhereClause {
+                has_where_token: false,
+                predicates: ThinVec::new(),
+                span,
+            },
             span,
         }
     }
diff --git a/compiler/rustc_parse/src/parser/generics.rs b/compiler/rustc_parse/src/parser/generics.rs
index 0eaa029a20d..04b7703ff04 100644
--- a/compiler/rustc_parse/src/parser/generics.rs
+++ b/compiler/rustc_parse/src/parser/generics.rs
@@ -258,7 +258,7 @@ impl<'a> Parser<'a> {
             params,
             where_clause: WhereClause {
                 has_where_token: false,
-                predicates: Vec::new(),
+                predicates: ThinVec::new(),
                 span: self.prev_token.span.shrink_to_hi(),
             },
             span,
@@ -288,7 +288,7 @@ impl<'a> Parser<'a> {
     ) -> PResult<'a, (WhereClause, Option<Vec<ast::FieldDef>>)> {
         let mut where_clause = WhereClause {
             has_where_token: false,
-            predicates: Vec::new(),
+            predicates: ThinVec::new(),
             span: self.prev_token.span.shrink_to_hi(),
         };
         let mut tuple_struct_body = None;
diff --git a/tests/ui/stats/hir-stats.stderr b/tests/ui/stats/hir-stats.stderr
index 6d2d1cb15a4..47d3382fc64 100644
--- a/tests/ui/stats/hir-stats.stderr
+++ b/tests/ui/stats/hir-stats.stderr
@@ -8,52 +8,52 @@ ast-stats-1 GenericArgs               56 ( 0.8%)             1            56
 ast-stats-1 - AngleBracketed            56 ( 0.8%)             1
 ast-stats-1 Crate                     56 ( 0.8%)             1            56
 ast-stats-1 Attribute                 64 ( 0.9%)             2            32
-ast-stats-1 - Normal                    32 ( 0.4%)             1
-ast-stats-1 - DocComment                32 ( 0.4%)             1
+ast-stats-1 - Normal                    32 ( 0.5%)             1
+ast-stats-1 - DocComment                32 ( 0.5%)             1
 ast-stats-1 Local                     72 ( 1.0%)             1            72
-ast-stats-1 Arm                       96 ( 1.3%)             2            48
-ast-stats-1 ForeignItem               96 ( 1.3%)             1            96
-ast-stats-1 - Fn                        96 ( 1.3%)             1
-ast-stats-1 FieldDef                 160 ( 2.2%)             2            80
-ast-stats-1 Stmt                     160 ( 2.2%)             5            32
-ast-stats-1 - Local                     32 ( 0.4%)             1
-ast-stats-1 - MacCall                   32 ( 0.4%)             1
-ast-stats-1 - Expr                      96 ( 1.3%)             3
-ast-stats-1 Param                    160 ( 2.2%)             4            40
+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 FieldDef                 160 ( 2.3%)             2            80
+ast-stats-1 Stmt                     160 ( 2.3%)             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 Param                    160 ( 2.3%)             4            40
 ast-stats-1 FnDecl                   200 ( 2.8%)             5            40
-ast-stats-1 GenericBound             224 ( 3.1%)             4            56
-ast-stats-1 - Trait                    224 ( 3.1%)             4
-ast-stats-1 Variant                  240 ( 3.3%)             2           120
-ast-stats-1 Block                    288 ( 4.0%)             6            48
-ast-stats-1 AssocItem                416 ( 5.8%)             4           104
-ast-stats-1 - Type                     208 ( 2.9%)             2
-ast-stats-1 - Fn                       208 ( 2.9%)             2
-ast-stats-1 GenericParam             480 ( 6.7%)             5            96
-ast-stats-1 Expr                     576 ( 8.0%)             8            72
+ast-stats-1 GenericBound             224 ( 3.2%)             4            56
+ast-stats-1 - Trait                    224 ( 3.2%)             4
+ast-stats-1 Variant                  240 ( 3.4%)             2           120
+ast-stats-1 Block                    288 ( 4.1%)             6            48
+ast-stats-1 AssocItem                416 ( 5.9%)             4           104
+ast-stats-1 - Type                     208 ( 3.0%)             2
+ast-stats-1 - Fn                       208 ( 3.0%)             2
+ast-stats-1 GenericParam             480 ( 6.8%)             5            96
+ast-stats-1 Expr                     576 ( 8.2%)             8            72
 ast-stats-1 - Path                      72 ( 1.0%)             1
 ast-stats-1 - Match                     72 ( 1.0%)             1
 ast-stats-1 - Struct                    72 ( 1.0%)             1
 ast-stats-1 - Lit                      144 ( 2.0%)             2
-ast-stats-1 - Block                    216 ( 3.0%)             3
-ast-stats-1 Pat                      616 ( 8.6%)             7            88
+ast-stats-1 - Block                    216 ( 3.1%)             3
+ast-stats-1 Pat                      616 ( 8.7%)             7            88
 ast-stats-1 - Struct                    88 ( 1.2%)             1
 ast-stats-1 - Wild                      88 ( 1.2%)             1
-ast-stats-1 - Ident                    440 ( 6.1%)             5
-ast-stats-1 PathSegment              720 (10.0%)            30            24
-ast-stats-1 Ty                       896 (12.5%)            14            64
+ast-stats-1 - Ident                    440 ( 6.2%)             5
+ast-stats-1 PathSegment              720 (10.2%)            30            24
+ast-stats-1 Ty                       896 (12.7%)            14            64
 ast-stats-1 - Ptr                       64 ( 0.9%)             1
 ast-stats-1 - Ref                       64 ( 0.9%)             1
 ast-stats-1 - ImplicitSelf             128 ( 1.8%)             2
-ast-stats-1 - Path                     640 ( 8.9%)            10
-ast-stats-1 Item                   1_512 (21.0%)             9           168
-ast-stats-1 - Trait                    168 ( 2.3%)             1
-ast-stats-1 - Enum                     168 ( 2.3%)             1
-ast-stats-1 - ForeignMod               168 ( 2.3%)             1
-ast-stats-1 - Impl                     168 ( 2.3%)             1
-ast-stats-1 - Fn                       336 ( 4.7%)             2
-ast-stats-1 - Use                      504 ( 7.0%)             3
+ast-stats-1 - Path                     640 ( 9.1%)            10
+ast-stats-1 Item                   1_368 (19.4%)             9           152
+ast-stats-1 - Trait                    152 ( 2.2%)             1
+ast-stats-1 - Enum                     152 ( 2.2%)             1
+ast-stats-1 - ForeignMod               152 ( 2.2%)             1
+ast-stats-1 - Impl                     152 ( 2.2%)             1
+ast-stats-1 - Fn                       304 ( 4.3%)             2
+ast-stats-1 - Use                      456 ( 6.5%)             3
 ast-stats-1 ----------------------------------------------------------------
-ast-stats-1 Total                  7_192
+ast-stats-1 Total                  7_048
 ast-stats-1
 ast-stats-2 POST EXPANSION AST STATS
 ast-stats-2 Name                Accumulated Size         Count     Item Size
@@ -68,52 +68,52 @@ ast-stats-2 Local                     72 ( 0.9%)             1            72
 ast-stats-2 Arm                       96 ( 1.2%)             2            48
 ast-stats-2 ForeignItem               96 ( 1.2%)             1            96
 ast-stats-2 - Fn                        96 ( 1.2%)             1
-ast-stats-2 InlineAsm                120 ( 1.5%)             1           120
-ast-stats-2 Attribute                128 ( 1.6%)             4            32
+ast-stats-2 InlineAsm                120 ( 1.6%)             1           120
+ast-stats-2 Attribute                128 ( 1.7%)             4            32
 ast-stats-2 - DocComment                32 ( 0.4%)             1
 ast-stats-2 - Normal                    96 ( 1.2%)             3
-ast-stats-2 FieldDef                 160 ( 2.0%)             2            80
-ast-stats-2 Stmt                     160 ( 2.0%)             5            32
+ast-stats-2 FieldDef                 160 ( 2.1%)             2            80
+ast-stats-2 Stmt                     160 ( 2.1%)             5            32
 ast-stats-2 - Local                     32 ( 0.4%)             1
 ast-stats-2 - Semi                      32 ( 0.4%)             1
 ast-stats-2 - Expr                      96 ( 1.2%)             3
-ast-stats-2 Param                    160 ( 2.0%)             4            40
-ast-stats-2 FnDecl                   200 ( 2.5%)             5            40
+ast-stats-2 Param                    160 ( 2.1%)             4            40
+ast-stats-2 FnDecl                   200 ( 2.6%)             5            40
 ast-stats-2 GenericBound             224 ( 2.9%)             4            56
 ast-stats-2 - Trait                    224 ( 2.9%)             4
 ast-stats-2 Variant                  240 ( 3.1%)             2           120
-ast-stats-2 Block                    288 ( 3.7%)             6            48
-ast-stats-2 AssocItem                416 ( 5.3%)             4           104
-ast-stats-2 - Type                     208 ( 2.6%)             2
-ast-stats-2 - Fn                       208 ( 2.6%)             2
-ast-stats-2 GenericParam             480 ( 6.1%)             5            96
-ast-stats-2 Pat                      616 ( 7.8%)             7            88
+ast-stats-2 Block                    288 ( 3.8%)             6            48
+ast-stats-2 AssocItem                416 ( 5.4%)             4           104
+ast-stats-2 - Type                     208 ( 2.7%)             2
+ast-stats-2 - Fn                       208 ( 2.7%)             2
+ast-stats-2 GenericParam             480 ( 6.2%)             5            96
+ast-stats-2 Pat                      616 ( 8.0%)             7            88
 ast-stats-2 - Struct                    88 ( 1.1%)             1
 ast-stats-2 - Wild                      88 ( 1.1%)             1
-ast-stats-2 - Ident                    440 ( 5.6%)             5
-ast-stats-2 Expr                     648 ( 8.2%)             9            72
+ast-stats-2 - Ident                    440 ( 5.7%)             5
+ast-stats-2 Expr                     648 ( 8.4%)             9            72
 ast-stats-2 - Path                      72 ( 0.9%)             1
 ast-stats-2 - Match                     72 ( 0.9%)             1
 ast-stats-2 - Struct                    72 ( 0.9%)             1
 ast-stats-2 - InlineAsm                 72 ( 0.9%)             1
-ast-stats-2 - Lit                      144 ( 1.8%)             2
-ast-stats-2 - Block                    216 ( 2.7%)             3
-ast-stats-2 PathSegment              792 (10.1%)            33            24
-ast-stats-2 Ty                       896 (11.4%)            14            64
+ast-stats-2 - Lit                      144 ( 1.9%)             2
+ast-stats-2 - Block                    216 ( 2.8%)             3
+ast-stats-2 PathSegment              792 (10.3%)            33            24
+ast-stats-2 Ty                       896 (11.7%)            14            64
 ast-stats-2 - Ptr                       64 ( 0.8%)             1
 ast-stats-2 - Ref                       64 ( 0.8%)             1
-ast-stats-2 - ImplicitSelf             128 ( 1.6%)             2
-ast-stats-2 - Path                     640 ( 8.1%)            10
-ast-stats-2 Item                   1_848 (23.5%)            11           168
-ast-stats-2 - Trait                    168 ( 2.1%)             1
-ast-stats-2 - Enum                     168 ( 2.1%)             1
-ast-stats-2 - ExternCrate              168 ( 2.1%)             1
-ast-stats-2 - ForeignMod               168 ( 2.1%)             1
-ast-stats-2 - Impl                     168 ( 2.1%)             1
-ast-stats-2 - Fn                       336 ( 4.3%)             2
-ast-stats-2 - Use                      672 ( 8.6%)             4
+ast-stats-2 - ImplicitSelf             128 ( 1.7%)             2
+ast-stats-2 - Path                     640 ( 8.3%)            10
+ast-stats-2 Item                   1_672 (21.8%)            11           152
+ast-stats-2 - Trait                    152 ( 2.0%)             1
+ast-stats-2 - Enum                     152 ( 2.0%)             1
+ast-stats-2 - ExternCrate              152 ( 2.0%)             1
+ast-stats-2 - ForeignMod               152 ( 2.0%)             1
+ast-stats-2 - Impl                     152 ( 2.0%)             1
+ast-stats-2 - Fn                       304 ( 4.0%)             2
+ast-stats-2 - Use                      608 ( 7.9%)             4
 ast-stats-2 ----------------------------------------------------------------
-ast-stats-2 Total                  7_856
+ast-stats-2 Total                  7_680
 ast-stats-2
 hir-stats HIR STATS
 hir-stats Name                Accumulated Size         Count     Item Size