Lower case some feature gate error messages

src/libsyntax/feature_gate.rs

@@ -1355,17 +1355,17 @@ pub const EXPLAIN_LITERAL_MATCHER: &'static str =
     ":literal fragment specifier is experimental and subject to change";
 
 pub const EXPLAIN_UNSIZED_TUPLE_COERCION: &'static str =
-    "Unsized tuple coercion is not stable enough for use and is subject to change";
+    "unsized tuple coercion is not stable enough for use and is subject to change";
 
 pub const EXPLAIN_MACRO_AT_MOST_ONCE_REP: &'static str =
-    "Using the `?` macro Kleene operator for \"at most one\" repetition is unstable";
+    "using the `?` macro Kleene operator for \"at most one\" repetition is unstable";
 
 pub const EXPLAIN_MACROS_IN_EXTERN: &'static str =
-    "Macro invocations in `extern {}` blocks are experimental.";
+    "macro invocations in `extern {}` blocks are experimental.";
 
 // mention proc-macros when enabled
 pub const EXPLAIN_PROC_MACROS_IN_EXTERN: &'static str =
-    "Macro and proc-macro invocations in `extern {}` blocks are experimental.";
+    "macro and proc-macro invocations in `extern {}` blocks are experimental.";
 
 struct PostExpansionVisitor<'a> {
     context: &'a Context<'a>,

src/test/compile-fail-fulldeps/proc-macro/macros-in-extern.rs

@@ -26,13 +26,13 @@ fn main() {
 #[link(name = "rust_test_helpers", kind = "static")]
 extern {
     #[no_output]
-    //~^ ERROR Macro and proc-macro invocations in `extern {}` blocks are experimental.
+    //~^ ERROR macro and proc-macro invocations in `extern {}` blocks are experimental.
     fn some_definitely_unknown_symbol_which_should_be_removed();
 
     #[nop_attr]
-    //~^ ERROR Macro and proc-macro invocations in `extern {}` blocks are experimental.
+    //~^ ERROR macro and proc-macro invocations in `extern {}` blocks are experimental.
     fn rust_get_test_int() -> isize;
 
     emit_input!(fn rust_dbg_extern_identity_u32(arg: u32) -> u32;);
-    //~^ ERROR Macro and proc-macro invocations in `extern {}` blocks are experimental.
+    //~^ ERROR macro and proc-macro invocations in `extern {}` blocks are experimental.
 }

src/test/compile-fail/macros-in-extern.rs

@@ -34,9 +34,9 @@ fn main() {
 #[link(name = "rust_test_helpers", kind = "static")]
 extern {
     returns_isize!(rust_get_test_int);
-    //~^ ERROR Macro invocations in `extern {}` blocks are experimental.
+    //~^ ERROR macro invocations in `extern {}` blocks are experimental.
     takes_u32_returns_u32!(rust_dbg_extern_identity_u32);
-    //~^ ERROR Macro invocations in `extern {}` blocks are experimental.
+    //~^ ERROR macro invocations in `extern {}` blocks are experimental.
     emits_nothing!();
-    //~^ ERROR Macro invocations in `extern {}` blocks are experimental.
+    //~^ ERROR macro invocations in `extern {}` blocks are experimental.
 }

src/test/ui/feature-gate-macro_at_most_once_rep.rs

@@ -12,7 +12,7 @@
 // gate is not used.
 
 macro_rules! m { ($(a)?) => {} }
-//~^ ERROR Using the `?` macro Kleene operator for "at most one" repetition is unstable
+//~^ ERROR using the `?` macro Kleene operator for "at most one" repetition is unstable
 
 fn main() {
     m!();

src/test/ui/feature-gate-macro_at_most_once_rep.stderr

@@ -1,4 +1,4 @@
-error[E0658]: Using the `?` macro Kleene operator for "at most one" repetition is unstable (see issue #48075)
+error[E0658]: using the `?` macro Kleene operator for "at most one" repetition is unstable (see issue #48075)
   --> $DIR/feature-gate-macro_at_most_once_rep.rs:14:20
    |
 LL | macro_rules! m { ($(a)?) => {} }

src/test/ui/feature-gate-macros_in_extern.rs

@@ -27,9 +27,9 @@ macro_rules! emits_nothing(
 #[link(name = "rust_test_helpers", kind = "static")]
 extern {
     returns_isize!(rust_get_test_int);
-    //~^ ERROR Macro invocations in `extern {}` blocks are experimental.
+    //~^ ERROR macro invocations in `extern {}` blocks are experimental.
     takes_u32_returns_u32!(rust_dbg_extern_identity_u32);
-    //~^ ERROR Macro invocations in `extern {}` blocks are experimental.
+    //~^ ERROR macro invocations in `extern {}` blocks are experimental.
     emits_nothing!();
-    //~^ ERROR Macro invocations in `extern {}` blocks are experimental.
+    //~^ ERROR macro invocations in `extern {}` blocks are experimental.
 }

src/test/ui/feature-gate-macros_in_extern.stderr

@@ -1,20 +1,20 @@
-error[E0658]: Macro invocations in `extern {}` blocks are experimental. (see issue #49476)
+error[E0658]: macro invocations in `extern {}` blocks are experimental. (see issue #49476)
   --> $DIR/feature-gate-macros_in_extern.rs:29:5
    |
 LL |     returns_isize!(rust_get_test_int);
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = help: add #![feature(macros_in_extern)] to the crate attributes to enable
 
-error[E0658]: Macro invocations in `extern {}` blocks are experimental. (see issue #49476)
+error[E0658]: macro invocations in `extern {}` blocks are experimental. (see issue #49476)
   --> $DIR/feature-gate-macros_in_extern.rs:31:5
    |
 LL |     takes_u32_returns_u32!(rust_dbg_extern_identity_u32);
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = help: add #![feature(macros_in_extern)] to the crate attributes to enable
 
-error[E0658]: Macro invocations in `extern {}` blocks are experimental. (see issue #49476)
+error[E0658]: macro invocations in `extern {}` blocks are experimental. (see issue #49476)
   --> $DIR/feature-gate-macros_in_extern.rs:33:5
    |
 LL |     emits_nothing!();

src/test/ui/feature-gate-unsized_tuple_coercion.rs

@@ -10,5 +10,5 @@
 
 fn main() {
     let _ : &(Send,) = &((),);
-    //~^ ERROR Unsized tuple coercion is not stable enough
+    //~^ ERROR unsized tuple coercion is not stable enough
 }

src/test/ui/feature-gate-unsized_tuple_coercion.stderr

@@ -1,4 +1,4 @@
-error[E0658]: Unsized tuple coercion is not stable enough for use and is subject to change (see issue #42877)
+error[E0658]: unsized tuple coercion is not stable enough for use and is subject to change (see issue #42877)
   --> $DIR/feature-gate-unsized_tuple_coercion.rs:12:24
    |
 LL |     let _ : &(Send,) = &((),);