Auto merge of rust-lang#107584 - matthiaskrgr:rollup-vav4ljz, r=matthiaskrgr

Rollup of 5 pull requests

Successful merges:

 - rust-lang#107201 (Remove confusing 'while checking' note from opaque future type mismatches)
 - rust-lang#107312 (Add Style Guide rules for let-else statements)
 - rust-lang#107488 (Fix syntax in `-Zunpretty-expanded` output for derived `PartialEq`.)
 - rust-lang#107531 (Inline CSS background images directly into the CSS)
 - rust-lang#107576 (Add proc-macro boilerplate to crt-static test)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

Author: bors

Diff for: compiler/rustc_builtin_macros/src/deriving/cmp/partial_eq.rs

@@ -29,16 +29,30 @@ pub fn expand_deriving_partial_eq(
                         cx.span_bug(field.span, "not exactly 2 arguments in `derive(PartialEq)`");
                     };
 
-                    // We received `&T` arguments. Convert them to `T` by
-                    // stripping `&` or adding `*`. This isn't necessary for
-                    // type checking, but it results in much better error
-                    // messages if something goes wrong.
+                    // We received arguments of type `&T`. Convert them to type `T` by stripping
+                    // any leading `&` or adding `*`. This isn't necessary for type checking, but
+                    // it results in better error messages if something goes wrong.
+                    //
+                    // Note: for arguments that look like `&{ x }`, which occur with packed
+                    // structs, this would cause expressions like `{ self.x } == { other.x }`,
+                    // which isn't valid Rust syntax. This wouldn't break compilation because these
+                    // AST nodes are constructed within the compiler. But it would mean that code
+                    // printed by `-Zunpretty=expanded` (or `cargo expand`) would have invalid
+                    // syntax, which would be suboptimal. So we wrap these in parens, giving
+                    // `({ self.x }) == ({ other.x })`, which is valid syntax.
                     let convert = |expr: &P<Expr>| {
                         if let ExprKind::AddrOf(BorrowKind::Ref, Mutability::Not, inner) =
                             &expr.kind
                         {
-                            inner.clone()
+                            if let ExprKind::Block(..) = &inner.kind {
+                                // `&{ x }` form: remove the `&`, add parens.
+                                cx.expr_paren(field.span, inner.clone())
+                            } else {
+                                // `&x` form: remove the `&`.
+                                inner.clone()
+                            }
                         } else {
+                            // No leading `&`: add a leading `*`.
                             cx.expr_deref(field.span, expr.clone())
                         }
                     };

Diff for: compiler/rustc_expand/src/build.rs

@@ -272,6 +272,10 @@ impl<'a> ExtCtxt<'a> {
         self.expr(sp, ast::ExprKind::AddrOf(ast::BorrowKind::Ref, ast::Mutability::Not, e))
     }
 
+    pub fn expr_paren(&self, sp: Span, e: P<ast::Expr>) -> P<ast::Expr> {
+        self.expr(sp, ast::ExprKind::Paren(e))
+    }
+
     pub fn expr_call(
         &self,
         span: Span,

Diff for: compiler/rustc_infer/src/infer/error_reporting/mod.rs

@@ -60,7 +60,7 @@ use crate::traits::{
 
 use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
 use rustc_errors::{pluralize, struct_span_err, Diagnostic, ErrorGuaranteed, IntoDiagnosticArg};
-use rustc_errors::{Applicability, DiagnosticBuilder, DiagnosticStyledString, MultiSpan};
+use rustc_errors::{Applicability, DiagnosticBuilder, DiagnosticStyledString};
 use rustc_hir as hir;
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::{DefId, LocalDefId};
@@ -1470,51 +1470,17 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                 for (key, values) in types.iter() {
                     let count = values.len();
                     let kind = key.descr();
-                    let mut returned_async_output_error = false;
                     for &sp in values {
-                        if sp.is_desugaring(DesugaringKind::Async) && !returned_async_output_error {
-                            if [sp] != err.span.primary_spans() {
-                                let mut span: MultiSpan = sp.into();
-                                span.push_span_label(
-                                    sp,
-                                    format!(
-                                        "checked the `Output` of this `async fn`, {}{} {}{}",
-                                        if count > 1 { "one of the " } else { "" },
-                                        target,
-                                        kind,
-                                        pluralize!(count),
-                                    ),
-                                );
-                                err.span_note(
-                                    span,
-                                    "while checking the return type of the `async fn`",
-                                );
-                            } else {
-                                err.span_label(
-                                    sp,
-                                    format!(
-                                        "checked the `Output` of this `async fn`, {}{} {}{}",
-                                        if count > 1 { "one of the " } else { "" },
-                                        target,
-                                        kind,
-                                        pluralize!(count),
-                                    ),
-                                );
-                                err.note("while checking the return type of the `async fn`");
-                            }
-                            returned_async_output_error = true;
-                        } else {
-                            err.span_label(
-                                sp,
-                                format!(
-                                    "{}{} {}{}",
-                                    if count == 1 { "the " } else { "one of the " },
-                                    target,
-                                    kind,
-                                    pluralize!(count),
-                                ),
-                            );
-                        }
+                        err.span_label(
+                            sp,
+                            format!(
+                                "{}{} {}{}",
+                                if count == 1 { "the " } else { "one of the " },
+                                target,
+                                kind,
+                                pluralize!(count),
+                            ),
+                        );
                     }
                 }
             }
@@ -1537,7 +1503,11 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                     //    |
                     //    = note: expected unit type `()`
                     //                 found closure `[closure@$DIR/issue-20862.rs:2:5: 2:14 x:_]`
-                    if !self.ignore_span.overlaps(span) {
+                    //
+                    // Also ignore opaque `Future`s that come from async fns.
+                    if !self.ignore_span.overlaps(span)
+                        && !span.is_desugaring(DesugaringKind::Async)
+                    {
                         self.types.entry(kind).or_default().insert(span);
                     }
                 }

Diff for: src/doc/style-guide/src/statements.md

@@ -99,6 +99,84 @@ let Foo {
 );
 ```
 
+#### else blocks (let-else statements)
+
+If a let statement contains an `else` component, also known as a let-else statement,
+then the `else` component should be formatted according to the same rules as the `else` block
+in [control flow expressions (i.e. if-else, and if-let-else expressions)](./expressions.md#control-flow-expressions).
+Apply the same formatting rules to the components preceding
+the `else` block (i.e. the `let pattern: Type = initializer_expr ...` portion)
+as described [above](#let-statements)
+
+Similarly to if-else expressions, if the initializer
+expression is multi-lined, then the `else` keyword and opening brace of the block (i.e. `else {`)
+should be put on the same line as the end of the initializer
+expression with a preceding space if all the following are true:
+
+* The initializer expression ends with one or more closing
+  parentheses, square brackets, and/or braces
+* There is nothing else on that line
+* That line is not indented beyond the indent of the first line containing the `let` keyword
+
+For example:
+
+```rust
+let Some(x) = y.foo(
+    "abc",
+    fairly_long_identifier,
+    "def",
+    "123456",
+    "string",
+    "cheese",
+) else {
+    bar()
+}
+```
+
+Otherwise, the `else` keyword and opening brace should be placed on the next line after the end of the initializer expression, and should not be indented (the `else` keyword should be aligned with the `let` keyword).
+
+For example:
+
+```rust
+let Some(x) = abcdef()
+    .foo(
+        "abc",
+        some_really_really_really_long_ident,
+        "ident",
+        "123456",
+    )
+    .bar()
+    .baz()
+    .qux("fffffffffffffffff")
+else {
+    foo_bar()
+}
+```
+
+##### Single line let-else statements
+
+The entire let-else statement may be formatted on a single line if all the following are true:
+
+* the entire statement is *short*
+* the `else` block contains a single-line expression and no statements
+* the `else` block contains no comments
+* the let statement components preceding the `else` block can be formatted on a single line
+
+```rust
+let Some(1) = opt else { return };
+
+let Some(1) = opt else {
+    return;
+};
+
+let Some(1) = opt else {
+    // nope
+    return
+};
+```
+
+Formatters may allow users to configure the value of the threshold
+used to determine whether a let-else statement is *short*.
 
 ### Macros in statement position
 

Diff for: src/librustdoc/html/static/css/rustdoc.css

@@ -814,8 +814,11 @@ so that we can apply CSS-filters to change the arrow color in themes */
 	background-repeat: no-repeat;
 	background-size: 20px;
 	background-position: calc(100% - 2px) 56%;
-	/* image is black color */
-	background-image: url("down-arrow-927217e04c7463ac.svg");
+	/* down arrow (image is black color) */
+	background-image: url('data:image/svg+xml,<svg xmlns="http://www.w3.org/2000/svg" \
+	width="128" height="128" viewBox="-30 -20 176 176"><path d="M111,40.5L64,87.499L17,40.5" \
+	fill="none" stroke="black" strike-linecap="square" stroke-miterlimit="10" stroke-width="12"/> \
+	</svg>');
 	/* changes the arrow image color */
 	filter: var(--crate-search-div-filter);
 }
@@ -1444,7 +1447,10 @@ details.toggle > summary.hideme > span {
 }
 
 details.toggle > summary::before {
-	background: url("toggle-plus-1092eb4930d581b0.svg") no-repeat top left;
+	/* toggle plus */
+	background: url('data:image/svg+xml,<svg width="17" height="17" \
+shape-rendering="crispEdges" stroke="black" fill="none" xmlns="http://www.w3.org/2000/svg"><path \
+d="M5 2.5H2.5v12H5m7-12h2.5v12H12M5 8.5h7M8.5 12V8.625v0V5"/></svg>') no-repeat top left;
 	content: "";
 	cursor: pointer;
 	width: 16px;
@@ -1522,7 +1528,10 @@ details.toggle[open] > summary.hideme > span {
 }
 
 details.toggle[open] > summary::before {
-	background: url("toggle-minus-31bbd6e4c77f5c96.svg") no-repeat top left;
+	/* toggle minus */
+	background: url('data:image/svg+xml,<svg width="17" height="17" \
+shape-rendering="crispEdges" stroke="black" fill="none" xmlns="http://www.w3.org/2000/svg"><path \
+d="M5 2.5H2.5v12H5m7-12h2.5v12H12M5 8.5h7"/></svg>') no-repeat top left;
 }
 
 details.toggle[open] > summary::after {

Diff for: src/librustdoc/html/static/images/down-arrow.svg

@@ -102,9 +102,6 @@ static_files! {
     scrape_examples_js => "static/js/scrape-examples.js",
     wheel_svg => "static/images/wheel.svg",
     clipboard_svg => "static/images/clipboard.svg",
-    down_arrow_svg => "static/images/down-arrow.svg",
-    toggle_minus_png => "static/images/toggle-minus.svg",
-    toggle_plus_png => "static/images/toggle-plus.svg",
     copyright => "static/COPYRIGHT.txt",
     license_apache => "static/LICENSE-APACHE.txt",
     license_mit => "static/LICENSE-MIT.txt",

Diff for: src/librustdoc/html/static/images/toggle-minus.svg

@@ -6,11 +6,6 @@ LL |         take_u32(x)
    |         |
    |         arguments to this function are incorrect
    |
-note: while checking the return type of the `async fn`
-  --> $DIR/dont-suggest-missing-await.rs:7:24
-   |
-LL | async fn make_u32() -> u32 {
-   |                        ^^^ checked the `Output` of this `async fn`, found opaque type
    = note:     expected type `u32`
            found opaque type `impl Future<Output = u32>`
 note: function defined here

Diff for: src/librustdoc/html/static/images/toggle-plus.svg

@@ -21,16 +21,6 @@ LL |     fun(one(), two());
    |     |
    |     arguments to this function are incorrect
    |
-note: while checking the return type of the `async fn`
-  --> $DIR/generator-desc.rs:5:16
-   |
-LL | async fn one() {}
-   |                ^ checked the `Output` of this `async fn`, expected opaque type
-note: while checking the return type of the `async fn`
-  --> $DIR/generator-desc.rs:6:16
-   |
-LL | async fn two() {}
-   |                ^ checked the `Output` of this `async fn`, found opaque type
    = note: expected opaque type `impl Future<Output = ()>` (opaque type at <$DIR/generator-desc.rs:5:16>)
               found opaque type `impl Future<Output = ()>` (opaque type at <$DIR/generator-desc.rs:6:16>)
    = help: consider `await`ing on both `Future`s

Diff for: src/librustdoc/html/static_files.rs

@@ -54,9 +54,6 @@ async fn struct_() -> Struct {
 }
 
 async fn tuple() -> Tuple {
-    //~^ NOTE checked the `Output` of this `async fn`, expected opaque type
-    //~| NOTE while checking the return type of the `async fn`
-    //~| NOTE in this expansion of desugaring of `async` block or function
     Tuple(1i32)
 }
 

Diff for: tests/ui/async-await/dont-suggest-missing-await.stderr

@@ -11,7 +11,7 @@ LL |     foo().await?;
    |          ++++++
 
 error[E0277]: the `?` operator can only be applied to values that implement `Try`
-  --> $DIR/issue-61076.rs:65:5
+  --> $DIR/issue-61076.rs:62:5
    |
 LL |     t?;
    |     ^^ the `?` operator cannot be applied to type `T`
@@ -23,7 +23,7 @@ LL |     t.await?;
    |      ++++++
 
 error[E0609]: no field `0` on type `impl Future<Output = Tuple>`
-  --> $DIR/issue-61076.rs:74:26
+  --> $DIR/issue-61076.rs:71:26
    |
 LL |     let _: i32 = tuple().0;
    |                          ^ field not available in `impl Future`, but it is available in its `Output`
@@ -34,7 +34,7 @@ LL |     let _: i32 = tuple().await.0;
    |                         ++++++
 
 error[E0609]: no field `a` on type `impl Future<Output = Struct>`
-  --> $DIR/issue-61076.rs:78:28
+  --> $DIR/issue-61076.rs:75:28
    |
 LL |     let _: i32 = struct_().a;
    |                            ^ field not available in `impl Future`, but it is available in its `Output`
@@ -45,7 +45,7 @@ LL |     let _: i32 = struct_().await.a;
    |                           ++++++
 
 error[E0599]: no method named `method` found for opaque type `impl Future<Output = Struct>` in the current scope
-  --> $DIR/issue-61076.rs:82:15
+  --> $DIR/issue-61076.rs:79:15
    |
 LL |     struct_().method();
    |               ^^^^^^ method not found in `impl Future<Output = Struct>`
@@ -56,19 +56,14 @@ LL |     struct_().await.method();
    |               ++++++
 
 error[E0308]: mismatched types
-  --> $DIR/issue-61076.rs:91:9
+  --> $DIR/issue-61076.rs:88:9
    |
 LL |     match tuple() {
    |           ------- this expression has type `impl Future<Output = Tuple>`
 LL |
 LL |         Tuple(_) => {}
    |         ^^^^^^^^ expected opaque type, found `Tuple`
    |
-note: while checking the return type of the `async fn`
-  --> $DIR/issue-61076.rs:56:21
-   |
-LL | async fn tuple() -> Tuple {
-   |                     ^^^^^ checked the `Output` of this `async fn`, expected opaque type
    = note: expected opaque type `impl Future<Output = Tuple>`
                    found struct `Tuple`
 help: consider `await`ing on the `Future`