Auto merge of #81760 - tmiasko:debug-borrow, r=pnkfelix

Borrow builder only once in debug derive

Author: bors

compiler/rustc_builtin_macros/src/deriving/debug.rs

@@ -77,16 +77,17 @@ fn show_substructure(cx: &mut ExtCtxt<'_>, span: Span, substr: &Substructure<'_>
             // tuple struct/"normal" variant
             let fn_path_debug_tuple = cx.std_path(&[sym::fmt, sym::Formatter, sym::debug_tuple]);
             let expr = cx.expr_call_global(span, fn_path_debug_tuple, vec![fmt, name]);
-            stmts.push(cx.stmt_let(span, true, builder, expr));
+            let expr = make_mut_borrow(cx, span, expr);
+            stmts.push(cx.stmt_let(span, false, builder, expr));
 
             for field in fields {
                 // Use double indirection to make sure this works for unsized types
                 let field = cx.expr_addr_of(field.span, field.self_.clone());
                 let field = cx.expr_addr_of(field.span, field);
 
                 let fn_path_field = cx.std_path(&[sym::fmt, sym::DebugTuple, sym::field]);
-                let builder_recv = make_mut_borrow(cx, span, builder_expr.clone());
-                let expr = cx.expr_call_global(span, fn_path_field, vec![builder_recv, field]);
+                let expr =
+                    cx.expr_call_global(span, fn_path_field, vec![builder_expr.clone(), field]);
 
                 // Use `let _ = expr;` to avoid triggering the
                 // unused_results lint.
@@ -99,7 +100,8 @@ fn show_substructure(cx: &mut ExtCtxt<'_>, span: Span, substr: &Substructure<'_>
             // normal struct/struct variant
             let fn_path_debug_struct = cx.std_path(&[sym::fmt, sym::Formatter, sym::debug_struct]);
             let expr = cx.expr_call_global(span, fn_path_debug_struct, vec![fmt, name]);
-            stmts.push(cx.stmt_let(DUMMY_SP, true, builder, expr));
+            let expr = make_mut_borrow(cx, span, expr);
+            stmts.push(cx.stmt_let(DUMMY_SP, false, builder, expr));
 
             for field in fields {
                 let name = cx.expr_lit(
@@ -111,17 +113,18 @@ fn show_substructure(cx: &mut ExtCtxt<'_>, span: Span, substr: &Substructure<'_>
                 let fn_path_field = cx.std_path(&[sym::fmt, sym::DebugStruct, sym::field]);
                 let field = cx.expr_addr_of(field.span, field.self_.clone());
                 let field = cx.expr_addr_of(field.span, field);
-                let builder_recv = make_mut_borrow(cx, span, builder_expr.clone());
-                let expr =
-                    cx.expr_call_global(span, fn_path_field, vec![builder_recv, name, field]);
+                let expr = cx.expr_call_global(
+                    span,
+                    fn_path_field,
+                    vec![builder_expr.clone(), name, field],
+                );
                 stmts.push(stmt_let_underscore(cx, span, expr));
             }
             fn_path_finish = cx.std_path(&[sym::fmt, sym::DebugStruct, sym::finish]);
         }
     }
 
-    let builder_recv = make_mut_borrow(cx, span, builder_expr);
-    let expr = cx.expr_call_global(span, fn_path_finish, vec![builder_recv]);
+    let expr = cx.expr_call_global(span, fn_path_finish, vec![builder_expr]);
 
     stmts.push(cx.stmt_expr(expr));
     let block = cx.block(span, stmts);

src/test/run-make-fulldeps/coverage-spanview/expected_mir_dump.partial_eq/partial_eq.{impl#7}-fmt.-------.InstrumentCoverage.0.html

@@ -73,41 +73,38 @@
 4:17-4:22: @0[2]: _3 = &((*_1).0: usize)
 4:17-4:22: @0[4]: _4 = &((*_1).1: usize)
 4:17-4:22: @0[6]: _5 = &((*_1).2: usize)
-4:17-4:22: @0[9]: _7 = &mut (*_2)
-4:17-4:22: @0[12]: _9 = const "Version"
-4:17-4:22: @0[13]: _8 = &(*_9)
-4:17-4:22: @0.Call: _6 = std::fmt::Formatter::debug_struct(move _7, move _8) -> [return: bb1, unwind: bb6]
-4:17-4:22: @1[2]: FakeRead(ForLet, _6)
-4:17-4:22: @1[7]: _12 = &mut _6
-4:17-4:22: @1[8]: _11 = &mut (*_12)
-4:17-4:22: @1[11]: _14 = const "major"
-4:17-4:22: @1[12]: _13 = &(*_14)
-4:17-4:22: @1[17]: _18 = &(*_3)
-4:17-4:22: @1[18]: _17 = &_18
-4:17-4:22: @1[19]: _16 = &(*_17)
-4:17-4:22: @1[20]: _15 = move _16 as &dyn std::fmt::Debug (Pointer(Unsize))
-4:17-4:22: @1.Call: _10 = std::fmt::DebugStruct::field(move _11, move _13, move _15) -> [return: bb2, unwind: bb6]
-4:17-4:22: @2[11]: _21 = &mut _6
-4:17-4:22: @2[12]: _20 = &mut (*_21)
-4:17-4:22: @2[15]: _23 = const "minor"
-4:17-4:22: @2[16]: _22 = &(*_23)
-4:17-4:22: @2[21]: _27 = &(*_4)
-4:17-4:22: @2[22]: _26 = &_27
-4:17-4:22: @2[23]: _25 = &(*_26)
-4:17-4:22: @2[24]: _24 = move _25 as &dyn std::fmt::Debug (Pointer(Unsize))
-4:17-4:22: @2.Call: _19 = std::fmt::DebugStruct::field(move _20, move _22, move _24) -> [return: bb3, unwind: bb6]
-4:17-4:22: @3[11]: _30 = &mut _6
-4:17-4:22: @3[12]: _29 = &mut (*_30)
-4:17-4:22: @3[15]: _32 = const "patch"
-4:17-4:22: @3[16]: _31 = &(*_32)
-4:17-4:22: @3[21]: _36 = &(*_5)
-4:17-4:22: @3[22]: _35 = &_36
-4:17-4:22: @3[23]: _34 = &(*_35)
-4:17-4:22: @3[24]: _33 = move _34 as &dyn std::fmt::Debug (Pointer(Unsize))
-4:17-4:22: @3.Call: _28 = std::fmt::DebugStruct::field(move _29, move _31, move _33) -> [return: bb4, unwind: bb6]
-4:17-4:22: @4[10]: _38 = &mut _6
-4:17-4:22: @4[11]: _37 = &mut (*_38)
-4:17-4:22: @4.Call: _0 = std::fmt::DebugStruct::finish(move _37) -> [return: bb5, unwind: bb6]
+4:17-4:22: @0[10]: _8 = &mut (*_2)
+4:17-4:22: @0[13]: _10 = const "Version"
+4:17-4:22: @0[14]: _9 = &(*_10)
+4:17-4:22: @0.Call: _7 = std::fmt::Formatter::debug_struct(move _8, move _9) -> [return: bb1, unwind: bb6]
+4:17-4:22: @1[2]: _6 = &mut _7
+4:17-4:22: @1[3]: FakeRead(ForLet, _6)
+4:17-4:22: @1[7]: _12 = &mut (*_6)
+4:17-4:22: @1[10]: _14 = const "major"
+4:17-4:22: @1[11]: _13 = &(*_14)
+4:17-4:22: @1[16]: _18 = &(*_3)
+4:17-4:22: @1[17]: _17 = &_18
+4:17-4:22: @1[18]: _16 = &(*_17)
+4:17-4:22: @1[19]: _15 = move _16 as &dyn std::fmt::Debug (Pointer(Unsize))
+4:17-4:22: @1.Call: _11 = std::fmt::DebugStruct::field(move _12, move _13, move _15) -> [return: bb2, unwind: bb6]
+4:17-4:22: @2[9]: _20 = &mut (*_6)
+4:17-4:22: @2[12]: _22 = const "minor"
+4:17-4:22: @2[13]: _21 = &(*_22)
+4:17-4:22: @2[18]: _26 = &(*_4)
+4:17-4:22: @2[19]: _25 = &_26
+4:17-4:22: @2[20]: _24 = &(*_25)
+4:17-4:22: @2[21]: _23 = move _24 as &dyn std::fmt::Debug (Pointer(Unsize))
+4:17-4:22: @2.Call: _19 = std::fmt::DebugStruct::field(move _20, move _21, move _23) -> [return: bb3, unwind: bb6]
+4:17-4:22: @3[9]: _28 = &mut (*_6)
+4:17-4:22: @3[12]: _30 = const "patch"
+4:17-4:22: @3[13]: _29 = &(*_30)
+4:17-4:22: @3[18]: _34 = &(*_5)
+4:17-4:22: @3[19]: _33 = &_34
+4:17-4:22: @3[20]: _32 = &(*_33)
+4:17-4:22: @3[21]: _31 = move _32 as &dyn std::fmt::Debug (Pointer(Unsize))
+4:17-4:22: @3.Call: _27 = std::fmt::DebugStruct::field(move _28, move _29, move _31) -> [return: bb4, unwind: bb6]
+4:17-4:22: @4[8]: _35 = &mut (*_6)
+4:17-4:22: @4.Call: _0 = std::fmt::DebugStruct::finish(move _35) -> [return: bb5, unwind: bb6]
 4:22-4:22: @5.Return: return"><span class="annotation">@0,1,2,3,4,5⦊</span>Debug<span class="annotation">⦉@0,1,2,3,4,5</span></span></span></span></div>
 </body>
 </html>