[create-pull-request] automated change (#1340)

Co-authored-by: jskeet <[email protected]>

Author: github-actions[bot]

standard/README.md

@@ -644,16 +644,19 @@
     - [§16.4.8](structs.md#1648-field-initializers)  Field initializers
     - [§16.4.9](structs.md#1649-constructors)  Constructors
     - [§16.4.10](structs.md#16410-static-constructors)  Static constructors
-    - [§16.4.11](structs.md#16411-automatically-implemented-properties)  Automatically implemented properties
-    - [§16.4.12](structs.md#16412-safe-context-constraint)  Safe context constraint
-      - [§16.4.12.1](structs.md#164121-general)  General
-      - [§16.4.12.2](structs.md#164122-parameter-safe-context)  Parameter safe context
-      - [§16.4.12.3](structs.md#164123-local-variable-safe-context)  Local variable safe context
-      - [§16.4.12.4](structs.md#164124-field-safe-context)  Field safe context
-      - [§16.4.12.5](structs.md#164125-operators)  Operators
-      - [§16.4.12.6](structs.md#164126-method-and-property-invocation)  Method and property invocation
-      - [§16.4.12.7](structs.md#164127-stackalloc)  stackalloc
-      - [§16.4.12.8](structs.md#164128-constructor-invocations)  Constructor invocations
+    - [§16.4.11](structs.md#16411-properties)  Properties
+    - [§16.4.12](structs.md#16412-methods)  Methods
+    - [§16.4.13](structs.md#16413-indexers)  Indexers
+    - [§16.4.14](structs.md#16414-events)  Events
+    - [§16.4.15](structs.md#16415-safe-context-constraint)  Safe context constraint
+      - [§16.4.15.1](structs.md#164151-general)  General
+      - [§16.4.15.2](structs.md#164152-parameter-safe-context)  Parameter safe context
+      - [§16.4.15.3](structs.md#164153-local-variable-safe-context)  Local variable safe context
+      - [§16.4.15.4](structs.md#164154-field-safe-context)  Field safe context
+      - [§16.4.15.5](structs.md#164155-operators)  Operators
+      - [§16.4.15.6](structs.md#164156-method-and-property-invocation)  Method and property invocation
+      - [§16.4.15.7](structs.md#164157-stackalloc)  stackalloc
+      - [§16.4.15.8](structs.md#164158-constructor-invocations)  Constructor invocations
 - [§17](arrays.md#17-arrays)  Arrays
   - [§17.1](arrays.md#171-general)  General
   - [§17.2](arrays.md#172-array-types)  Array types

standard/classes.md

@@ -2133,7 +2133,7 @@ Grammar notes:
 
 > *Note*: The overlapping of, and priority between, alternatives here is solely for descriptive convenience; the grammar rules could be elaborated to remove the overlap. ANTLR, and other grammar systems, adopt the same convenience and so *method_body* has the specified semantics automatically. *end note*
 
-A *method_declaration* may include a set of *attributes* ([§22](attributes.md#22-attributes)) and one of the permitted kinds of declared accessibility ([§15.3.6](classes.md#1536-access-modifiers)), the `new` ([§15.3.5](classes.md#1535-the-new-modifier)), `static` ([§15.6.3](classes.md#1563-static-and-instance-methods)), `virtual` ([§15.6.4](classes.md#1564-virtual-methods)), `override` ([§15.6.5](classes.md#1565-override-methods)), `sealed` ([§15.6.6](classes.md#1566-sealed-methods)), `abstract` ([§15.6.7](classes.md#1567-abstract-methods)), `extern` ([§15.6.8](classes.md#1568-external-methods)) and `async` ([§15.15](classes.md#1515-async-functions)). Additionally a  *method_declaration* that is contained directly by a *struct_declaration* may include the `readonly` modifier (§cands-diffs-methods).
+A *method_declaration* may include a set of *attributes* ([§22](attributes.md#22-attributes)) and one of the permitted kinds of declared accessibility ([§15.3.6](classes.md#1536-access-modifiers)), the `new` ([§15.3.5](classes.md#1535-the-new-modifier)), `static` ([§15.6.3](classes.md#1563-static-and-instance-methods)), `virtual` ([§15.6.4](classes.md#1564-virtual-methods)), `override` ([§15.6.5](classes.md#1565-override-methods)), `sealed` ([§15.6.6](classes.md#1566-sealed-methods)), `abstract` ([§15.6.7](classes.md#1567-abstract-methods)), `extern` ([§15.6.8](classes.md#1568-external-methods)) and `async` ([§15.15](classes.md#1515-async-functions)). Additionally a  *method_declaration* that is contained directly by a *struct_declaration* may include the `readonly` modifier ([§16.4.12](structs.md#16412-methods)).
 
 A declaration has a valid combination of modifiers if all of the following are true:
 
@@ -3303,7 +3303,7 @@ ref_property_body
 
 *unsafe_modifier* ([§23.2](unsafe-code.md#232-unsafe-contexts)) is only available in unsafe code ([§23](unsafe-code.md#23-unsafe-code)).
 
-A *property_declaration* may include a set of *attributes* ([§22](attributes.md#22-attributes)) and any one of the permitted kinds of declared accessibility ([§15.3.6](classes.md#1536-access-modifiers)), the `new` ([§15.3.5](classes.md#1535-the-new-modifier)), `static` ([§15.7.2](classes.md#1572-static-and-instance-properties)), `virtual` ([§15.6.4](classes.md#1564-virtual-methods), [§15.7.6](classes.md#1576-virtual-sealed-override-and-abstract-accessors)), `override` ([§15.6.5](classes.md#1565-override-methods), [§15.7.6](classes.md#1576-virtual-sealed-override-and-abstract-accessors)), `sealed` ([§15.6.6](classes.md#1566-sealed-methods)), `abstract` ([§15.6.7](classes.md#1567-abstract-methods), [§15.7.6](classes.md#1576-virtual-sealed-override-and-abstract-accessors)) and `extern` ([§15.6.8](classes.md#1568-external-methods)). Additionally a *property_declaration* that is contained directly by a *struct_declaration* may include the `readonly` modifier (§16.4.11).
+A *property_declaration* may include a set of *attributes* ([§22](attributes.md#22-attributes)) and any one of the permitted kinds of declared accessibility ([§15.3.6](classes.md#1536-access-modifiers)), the `new` ([§15.3.5](classes.md#1535-the-new-modifier)), `static` ([§15.7.2](classes.md#1572-static-and-instance-properties)), `virtual` ([§15.6.4](classes.md#1564-virtual-methods), [§15.7.6](classes.md#1576-virtual-sealed-override-and-abstract-accessors)), `override` ([§15.6.5](classes.md#1565-override-methods), [§15.7.6](classes.md#1576-virtual-sealed-override-and-abstract-accessors)), `sealed` ([§15.6.6](classes.md#1566-sealed-methods)), `abstract` ([§15.6.7](classes.md#1567-abstract-methods), [§15.7.6](classes.md#1576-virtual-sealed-override-and-abstract-accessors)) and `extern` ([§15.6.8](classes.md#1568-external-methods)). Additionally a *property_declaration* that is contained directly by a *struct_declaration* may include the `readonly` modifier ([§16.4.11](structs.md#16411-properties)).
 
 - The first declares a non-ref-valued property. Its value has type *type*. This kind of property may be readable and/or writeable.
 - The second declares a ref-valued property. Its value is a *variable_reference* ([§9.5](variables.md#95-variable-references)), that may be `readonly`, to a variable of type *type*. This kind of property is only readable.
@@ -3395,7 +3395,7 @@ For a ref-valued property the *ref_get_accessor_declaration* consists optional a
 The use of *accessor_modifier*s is governed by the following restrictions:
 
 - An *accessor_modifier* shall not be used in an interface or in an explicit interface member implementation.
-- The *accessor_modifier* `readonly` is permitted only in a *property_declaration* or *indexer_declaration* that is contained directly by a *struct_declaration* (§16.4.11, §cands-diffs-indexers).
+- The *accessor_modifier* `readonly` is permitted only in a *property_declaration* or *indexer_declaration* that is contained directly by a *struct_declaration* ([§16.4.11](structs.md#16411-properties), [§16.4.13](structs.md#16413-indexers)).
 - For a property or indexer that has no `override` modifier, an *accessor_modifier* is permitted only if the property or indexer has both a get and set accessor, and then is permitted only on one of those accessors.
 - For a property or indexer that includes an `override` modifier, an accessor shall match the *accessor_modifier*, if any, of the accessor being overridden.
 - The *accessor_modifier* shall declare an accessibility that is strictly more restrictive than the declared accessibility of the property or indexer itself. To be precise:
@@ -4048,7 +4048,7 @@ remove_accessor_declaration
 
 *unsafe_modifier* ([§23.2](unsafe-code.md#232-unsafe-contexts)) is only available in unsafe code ([§23](unsafe-code.md#23-unsafe-code)).
 
-An *event_declaration* may include a set of *attributes* ([§22](attributes.md#22-attributes)) and any one of the permitted kinds of declared accessibility ([§15.3.6](classes.md#1536-access-modifiers)), the `new` ([§15.3.5](classes.md#1535-the-new-modifier)), `static` ([§15.6.3](classes.md#1563-static-and-instance-methods), [§15.8.4](classes.md#1584-static-and-instance-events)), `virtual` ([§15.6.4](classes.md#1564-virtual-methods), [§15.8.5](classes.md#1585-virtual-sealed-override-and-abstract-accessors)), `override` ([§15.6.5](classes.md#1565-override-methods), [§15.8.5](classes.md#1585-virtual-sealed-override-and-abstract-accessors)), `sealed` ([§15.6.6](classes.md#1566-sealed-methods)), `abstract` ([§15.6.7](classes.md#1567-abstract-methods), [§15.8.5](classes.md#1585-virtual-sealed-override-and-abstract-accessors)) and `extern` ([§15.6.8](classes.md#1568-external-methods)) modifiers. Additionally an *event_declaration* that is contained directly by a *struct_declaration* may include the `readonly` modifier (§cands-diffs-methods).
+An *event_declaration* may include a set of *attributes* ([§22](attributes.md#22-attributes)) and any one of the permitted kinds of declared accessibility ([§15.3.6](classes.md#1536-access-modifiers)), the `new` ([§15.3.5](classes.md#1535-the-new-modifier)), `static` ([§15.6.3](classes.md#1563-static-and-instance-methods), [§15.8.4](classes.md#1584-static-and-instance-events)), `virtual` ([§15.6.4](classes.md#1564-virtual-methods), [§15.8.5](classes.md#1585-virtual-sealed-override-and-abstract-accessors)), `override` ([§15.6.5](classes.md#1565-override-methods), [§15.8.5](classes.md#1585-virtual-sealed-override-and-abstract-accessors)), `sealed` ([§15.6.6](classes.md#1566-sealed-methods)), `abstract` ([§15.6.7](classes.md#1567-abstract-methods), [§15.8.5](classes.md#1585-virtual-sealed-override-and-abstract-accessors)) and `extern` ([§15.6.8](classes.md#1568-external-methods)) modifiers. Additionally an *event_declaration* that is contained directly by a *struct_declaration* may include the `readonly` modifier ([§16.4.12](structs.md#16412-methods)).
 
 Event declarations are subject to the same rules as method declarations ([§15.6](classes.md#156-methods)) with regard to valid combinations of modifiers.
 
@@ -4331,7 +4331,7 @@ ref_indexer_body
 
 *unsafe_modifier* ([§23.2](unsafe-code.md#232-unsafe-contexts)) is only available in unsafe code ([§23](unsafe-code.md#23-unsafe-code)).
 
-An *indexer_declaration* may include a set of *attributes* ([§22](attributes.md#22-attributes)) and any one of the permitted kinds of declared accessibility ([§15.3.6](classes.md#1536-access-modifiers)), the `new` ([§15.3.5](classes.md#1535-the-new-modifier)), `virtual` ([§15.6.4](classes.md#1564-virtual-methods)), `override` ([§15.6.5](classes.md#1565-override-methods)), `sealed` ([§15.6.6](classes.md#1566-sealed-methods)), `abstract` ([§15.6.7](classes.md#1567-abstract-methods)) and `extern` ([§15.6.8](classes.md#1568-external-methods)) modifiers. Additionally an *indexer_declaration* that is contained directly by a *struct_declaration* may include the `readonly` modifier (§cands-diffs-methods).
+An *indexer_declaration* may include a set of *attributes* ([§22](attributes.md#22-attributes)) and any one of the permitted kinds of declared accessibility ([§15.3.6](classes.md#1536-access-modifiers)), the `new` ([§15.3.5](classes.md#1535-the-new-modifier)), `virtual` ([§15.6.4](classes.md#1564-virtual-methods)), `override` ([§15.6.5](classes.md#1565-override-methods)), `sealed` ([§15.6.6](classes.md#1566-sealed-methods)), `abstract` ([§15.6.7](classes.md#1567-abstract-methods)) and `extern` ([§15.6.8](classes.md#1568-external-methods)) modifiers. Additionally an *indexer_declaration* that is contained directly by a *struct_declaration* may include the `readonly` modifier ([§16.4.12](structs.md#16412-methods)).
 
 - The first declares a non-ref-valued indexer. Its value has type *type*. This kind of indexer may be readable and/or writeable.
 - The second declares a ref-valued indexer. Its value is a *variable_reference* ([§9.5](variables.md#95-variable-references)), that may be `readonly`, to a variable of type *type*. This kind of indexer is only readable.

standard/expressions.md

@@ -1811,7 +1811,7 @@ A *null_conditional_projection_initializer* is a restriction of *null_conditiona
 #### 12.8.9.1 General
 
 A null-forgiving expression’s value, type, classification ([§12.2](expressions.md#122-expression-classifications))
-and safe-context ([§16.4.12](structs.md#16412-safe-context-constraint)) is the value, type, classification and safe-context of its *primary_expression*.
+and safe-context ([§16.4.15](structs.md#16415-safe-context-constraint)) is the value, type, classification and safe-context of its *primary_expression*.
 
 ```ANTLR
 null_forgiving_expression
@@ -3288,7 +3288,7 @@ A *default_value_expression* is a constant expression ([§12.23](expressions.md#
 
 A stack allocation expression allocates a block of memory from the execution stack. The ***execution stack*** is an area of memory where local variables are stored. The execution stack is not part of the managed heap. The memory used for local variable storage is automatically recovered when the current function returns.
 
-The safe context rules for a stack allocation expression are described in [§16.4.12.7](structs.md#164127-stackalloc).
+The safe context rules for a stack allocation expression are described in [§16.4.15.7](structs.md#164157-stackalloc).
 
 ```ANTLR
 stackalloc_expression

standard/grammar.md

@@ -2087,6 +2087,7 @@ ref_method_modifier
     | 'override'
     | 'abstract'
     | 'extern'
+    | 'readonly'        // direct struct members only
     | unsafe_modifier   // unsafe code support
     ;
 
@@ -2169,6 +2170,7 @@ property_modifier
     | 'override'
     | 'abstract'
     | 'extern'
+    | 'readonly'        // direct struct members only
     | unsafe_modifier   // unsafe code support
     ;
     
@@ -2208,6 +2210,7 @@ accessor_modifier
     | 'internal' 'protected'
     | 'protected' 'private'
     | 'private' 'protected'
+    | 'readonly'        // direct struct members only
     ;
 
 accessor_body
@@ -2245,6 +2248,7 @@ event_modifier
     | 'override'
     | 'abstract'
     | 'extern'
+    | 'readonly'        // direct struct members only
     | unsafe_modifier   // unsafe code support
     ;
 
@@ -2278,6 +2282,7 @@ indexer_modifier
     | 'override'
     | 'abstract'
     | 'extern'
+    | 'readonly'        // direct struct members only
     | unsafe_modifier   // unsafe code support
     ;