Add some helper functions to LoweringContext.

compiler/rustc_ast_lowering/src/expr.rs

@@ -16,7 +16,7 @@
 use rustc_hir::definitions::DefPathData;
 use rustc_session::errors::report_lit_error;
 use rustc_span::source_map::{respan, DesugaringKind, Span, Spanned};
-use rustc_span::symbol::{sym, Ident};
+use rustc_span::symbol::{sym, Ident, Symbol};
 use rustc_span::DUMMY_SP;
 use thin_vec::thin_vec;
 
@@ -1757,6 +1757,43 @@ fn expr_unit(&mut self, sp: Span) -> &'hir hir::Expr<'hir> {
         self.arena.alloc(self.expr(sp, hir::ExprKind::Tup(&[])))
     }
 
+    pub(super) fn expr_usize(&mut self, sp: Span, value: usize) -> hir::Expr<'hir> {
+        self.expr(
+            sp,
+            hir::ExprKind::Lit(hir::Lit {
+                span: sp,
+                node: ast::LitKind::Int(
+                    value as u128,
+                    ast::LitIntType::Unsigned(ast::UintTy::Usize),
+                ),
+            }),
+        )
+    }
+
+    pub(super) fn expr_u32(&mut self, sp: Span, value: u32) -> hir::Expr<'hir> {
+        self.expr(
+            sp,
+            hir::ExprKind::Lit(hir::Lit {
+                span: sp,
+                node: ast::LitKind::Int(value.into(), ast::LitIntType::Unsigned(ast::UintTy::U32)),
+            }),
+        )
+    }
+
+    pub(super) fn expr_char(&mut self, sp: Span, value: char) -> hir::Expr<'hir> {
+        self.expr(sp, hir::ExprKind::Lit(hir::Lit { span: sp, node: ast::LitKind::Char(value) }))
+    }
+
+    pub(super) fn expr_str(&mut self, sp: Span, value: Symbol) -> hir::Expr<'hir> {
+        self.expr(
+            sp,
+            hir::ExprKind::Lit(hir::Lit {
+                span: sp,
+                node: ast::LitKind::Str(value, ast::StrStyle::Cooked),
+            }),
+        )
+    }
+
     fn expr_call_mut(
         &mut self,
         span: Span,
@@ -1808,6 +1845,27 @@ fn expr_lang_item_path(
         )
     }
 
+    /// `<LangItem>::name`
+    pub(super) fn expr_lang_item_type_relative(
+        &mut self,
+        span: Span,
+        lang_item: hir::LangItem,
+        name: Symbol,
+    ) -> hir::Expr<'hir> {
+        let path = hir::ExprKind::Path(hir::QPath::TypeRelative(
+            self.arena.alloc(self.ty(
+                span,
+                hir::TyKind::Path(hir::QPath::LangItem(lang_item, self.lower_span(span), None)),
+            )),
+            self.arena.alloc(hir::PathSegment::new(
+                Ident::new(name, span),
+                self.next_id(),
+                Res::Err,
+            )),
+        ));
+        self.expr(span, path)
+    }
+
     pub(super) fn expr_ident(
         &mut self,
         sp: Span,
@@ -1866,6 +1924,19 @@ pub(super) fn expr_block(&mut self, b: &'hir hir::Block<'hir>) -> hir::Expr<'hir
         self.expr(b.span, hir::ExprKind::Block(b, None))
     }
 
+    pub(super) fn expr_array_ref(
+        &mut self,
+        span: Span,
+        elements: &'hir [hir::Expr<'hir>],
+    ) -> hir::Expr<'hir> {
+        let addrof = hir::ExprKind::AddrOf(
+            hir::BorrowKind::Ref,
+            hir::Mutability::Not,
+            self.arena.alloc(self.expr(span, hir::ExprKind::Array(elements))),
+        );
+        self.expr(span, addrof)
+    }
+
     pub(super) fn expr(&mut self, span: Span, kind: hir::ExprKind<'hir>) -> hir::Expr<'hir> {
         let hir_id = self.next_id();
         hir::Expr { hir_id, kind, span: self.lower_span(span) }