parse pinned local variable declarations

Author: frank-king

compiler/rustc_mir_build/src/thir/pattern/check_match.rs

@@ -876,7 +876,7 @@ fn check_for_bindings_named_same_as_variants(
 ) {
     if let PatKind::Binding {
         name,
-        mode: BindingMode(ByRef::No, Mutability::Not),
+        mode: BindingMode(ByRef::No, _, Mutability::Not),
         subpattern: None,
         ty,
         ..

compiler/rustc_parse/messages.ftl

@@ -663,6 +663,8 @@ parse_note_mut_pattern_usage = `mut` may be followed by `variable` and `variable
 
 parse_note_pattern_alternatives_use_single_vert = alternatives in or-patterns are separated with `|`, not `||`
 
+parse_note_pin_pattern_usage = `pin mut` or `pin const` may be followed by `variable` and `variable @ pattern`
+
 parse_nul_in_c_str = null characters in C string literals are not supported
 
 parse_or_pattern_not_allowed_in_fn_parameters = top-level or-patterns are not allowed in function parameters
@@ -698,6 +700,11 @@ parse_pattern_on_wrong_side_of_at = pattern on wrong side of `@`
     .label_binding = binding on the right, should be on the left
     .suggestion = switch the order
 
+parse_pin_on_nested_ident_pattern = `pin {$mutbl}` must be attached to each individual binding
+    .suggestion = add `pin {$mutbl}` to each binding
+parse_pin_on_non_ident_pattern = `pin {$mutbl}` must be followed by a named binding
+    .suggestion = remove the `pin {$mutbl}` prefix
+
 parse_question_mark_in_type = invalid `?` in type
     .label = `?` is only allowed on expressions, not types
     .suggestion = if you meant to express that the type might not contain a value, use the `Option` wrapper type