Auto merge of #43726 - zackmdavis:extended_information_summer_block_party, r=GuillaumeGomez

E05XX odyssey

chipping away at the surface exposed by #43709

r? @GuillaumeGomez

Author: bors

src/librustc_passes/diagnostics.rs

@@ -223,12 +223,45 @@ To fix this, add a label specifying which loop is being broken out of:
 ```
 'foo: while break 'foo {}
 ```
+"##,
+
+E0571: r##"
+A `break` statement with an argument appeared in a non-`loop` loop.
+
+Example of erroneous code:
+
+```compile_fail,E0571
+# let mut i = 1;
+# fn satisfied(n: usize) -> bool { n % 23 == 0 }
+let result = while true {
+    if satisfied(i) {
+        break 2*i; // error: `break` with value from a `while` loop
+    }
+    i += 1;
+};
+```
+
+The `break` statement can take an argument (which will be the value of the loop
+expression if the `break` statement is executed) in `loop` loops, but not
+`for`, `while`, or `while let` loops.
+
+Make sure `break value;` statements only occur in `loop` loops:
+
+```
+# let mut i = 1;
+# fn satisfied(n: usize) -> bool { n % 23 == 0 }
+let result = loop { // ok!
+    if satisfied(i) {
+        break 2*i;
+    }
+    i += 1;
+};
+```
 "##
 }
 
 register_diagnostics! {
     E0226, // only a single explicit lifetime bound is permitted
     E0472, // asm! is unsupported on this target
     E0561, // patterns aren't allowed in function pointer types
-    E0571, // `break` with a value in a non-`loop`-loop
 }

src/libsyntax/diagnostic_list.rs

@@ -162,6 +162,63 @@ For more information about the cfg attribute, read:
 https://doc.rust-lang.org/reference.html#conditional-compilation
 "##,
 
+E0552: r##"
+A unrecognized representation attribute was used.
+
+Erroneous code example:
+
+```compile_fail,E0552
+#[repr(D)] // error: unrecognized representation hint
+struct MyStruct {
+    my_field: usize
+}
+```
+
+You can use a `repr` attribute to tell the compiler how you want a struct or
+enum to be laid out in memory.
+
+Make sure you're using one of the supported options:
+
+```
+#[repr(C)] // ok!
+struct MyStruct {
+    my_field: usize
+}
+```
+
+For more information about specifying representations, see the ["Alternative
+Representations" section] of the Rustonomicon.
+
+["Alternative Representations" section]: https://doc.rust-lang.org/nomicon/other-reprs.html
+"##,
+
+E0554: r##"
+Feature attributes are only allowed on the nightly release channel. Stable or
+beta compilers will not comply.
+
+Example of erroneous code (on a stable compiler):
+
+```ignore (depends on release channel)
+#![feature(non_ascii_idents)] // error: #![feature] may not be used on the
+                              //        stable release channel
+```
+
+If you need the feature, make sure to use a nightly release of the compiler
+(but be warned that the feature may be removed or altered in the future).
+"##,
+
+E0557: r##"
+A feature attribute named a feature that has been removed.
+
+Erroneous code example:
+
+```compile_fail,E0557
+#![feature(managed_boxes)] // error: feature has been removed
+```
+
+Delete the offending feature attribute.
+"##,
+
 E0558: r##"
 The `export_name` attribute was malformed.
 
@@ -300,11 +357,8 @@ register_diagnostics! {
     E0549, // rustc_deprecated attribute must be paired with either stable or unstable attribute
     E0550, // multiple deprecated attributes
     E0551, // incorrect meta item
-    E0552, // unrecognized representation hint
-    E0554, // #[feature] may not be used on the [] release channel
     E0555, // malformed feature attribute, expected #![feature(...)]
     E0556, // malformed feature, expected just one word
-    E0557, // feature has been removed
     E0584, // file for module `..` found at both .. and ..
     E0589, // invalid `repr(align)` attribute
 }

src/libsyntax/feature_gate.rs

@@ -1602,7 +1602,7 @@ fn maybe_stage_features(span_handler: &Handler, krate: &ast::Crate,
             if attr.check_name("feature") {
                 let release_channel = option_env!("CFG_RELEASE_CHANNEL").unwrap_or("(unknown)");
                 span_err!(span_handler, attr.span, E0554,
-                          "#[feature] may not be used on the {} release channel",
+                          "#![feature] may not be used on the {} release channel",
                           release_channel);
             }
         }