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SummaryOfTheGrammar.md

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Summary of the Grammar

Read the whole formal grammar.

Lexical Structure

Grammar of whitespace:

whitespace → whitespace-item whitespace?
whitespace-item → line-break
whitespace-item → inline-space
whitespace-item → comment
whitespace-item → multiline-comment
whitespace-item → U+0000, U+000B, or U+000C

line-break → U+000A
line-break → U+000D
line-break → U+000D followed by U+000A

inline-spaces → inline-space inline-spaces?
inline-space → U+0009 or U+0020

comment → // comment-text line-break
multiline-comment → /* multiline-comment-text */

comment-text → comment-text-item comment-text?
comment-text-item → Any Unicode scalar value except U+000A or U+000D

multiline-comment-text → multiline-comment-text-item multiline-comment-text?
multiline-comment-text-item → multiline-comment
multiline-comment-text-item → comment-text-item
multiline-comment-text-item → Any Unicode scalar value except /* or */

Grammar of an identifier:

identifier → identifier-head identifier-characters?
identifier → ` identifier-head identifier-characters? `
identifier → implicit-parameter-name
identifier → property-wrapper-projection
identifier-list → identifier | identifier , identifier-list

identifier-head → Upper- or lowercase letter A through Z
identifier-head → _
identifier-head → U+00A8, U+00AA, U+00AD, U+00AF, U+00B2–U+00B5, or U+00B7–U+00BA
identifier-head → U+00BC–U+00BE, U+00C0–U+00D6, U+00D8–U+00F6, or U+00F8–U+00FF
identifier-head → U+0100–U+02FF, U+0370–U+167F, U+1681–U+180D, or U+180F–U+1DBF
identifier-head → U+1E00–U+1FFF
identifier-head → U+200B–U+200D, U+202A–U+202E, U+203F–U+2040, U+2054, or U+2060–U+206F
identifier-head → U+2070–U+20CF, U+2100–U+218F, U+2460–U+24FF, or U+2776–U+2793
identifier-head → U+2C00–U+2DFF or U+2E80–U+2FFF
identifier-head → U+3004–U+3007, U+3021–U+302F, U+3031–U+303F, or U+3040–U+D7FF
identifier-head → U+F900–U+FD3D, U+FD40–U+FDCF, U+FDF0–U+FE1F, or U+FE30–U+FE44
identifier-head → U+FE47–U+FFFD
identifier-head → U+10000–U+1FFFD, U+20000–U+2FFFD, U+30000–U+3FFFD, or U+40000–U+4FFFD
identifier-head → U+50000–U+5FFFD, U+60000–U+6FFFD, U+70000–U+7FFFD, or U+80000–U+8FFFD
identifier-head → U+90000–U+9FFFD, U+A0000–U+AFFFD, U+B0000–U+BFFFD, or U+C0000–U+CFFFD
identifier-head → U+D0000–U+DFFFD or U+E0000–U+EFFFD

identifier-character → Digit 0 through 9
identifier-character → U+0300–U+036F, U+1DC0–U+1DFF, U+20D0–U+20FF, or U+FE20–U+FE2F
identifier-character → identifier-head
identifier-characters → identifier-character identifier-characters?

implicit-parameter-name → $ decimal-digits
property-wrapper-projection → $ identifier-characters

Grammar of a literal:

literal → numeric-literal | string-literal | regular-expression-literal | boolean-literal | nil-literal

numeric-literal → -? integer-literal | -? floating-point-literal
boolean-literal → true | false
nil-literal → nil

Grammar of an integer literal:

integer-literal → binary-literal
integer-literal → octal-literal
integer-literal → decimal-literal
integer-literal → hexadecimal-literal

binary-literal → 0b binary-digit binary-literal-characters?
binary-digit → Digit 0 or 1
binary-literal-character → binary-digit | _
binary-literal-characters → binary-literal-character binary-literal-characters?

octal-literal → 0o octal-digit octal-literal-characters?
octal-digit → Digit 0 through 7
octal-literal-character → octal-digit | _
octal-literal-characters → octal-literal-character octal-literal-characters?

decimal-literal → decimal-digit decimal-literal-characters?
decimal-digit → Digit 0 through 9
decimal-digits → decimal-digit decimal-digits?
decimal-literal-character → decimal-digit | _
decimal-literal-characters → decimal-literal-character decimal-literal-characters?

hexadecimal-literal → 0x hexadecimal-digit hexadecimal-literal-characters?
hexadecimal-digit → Digit 0 through 9, a through f, or A through F
hexadecimal-literal-character → hexadecimal-digit | _
hexadecimal-literal-characters → hexadecimal-literal-character hexadecimal-literal-characters?

Grammar of a floating-point literal:

floating-point-literal → decimal-literal decimal-fraction? decimal-exponent?
floating-point-literal → hexadecimal-literal hexadecimal-fraction? hexadecimal-exponent

decimal-fraction → . decimal-literal
decimal-exponent → floating-point-e sign? decimal-literal

hexadecimal-fraction → . hexadecimal-digit hexadecimal-literal-characters?
hexadecimal-exponent → floating-point-p sign? decimal-literal

floating-point-e → e | E
floating-point-p → p | P
sign → + | -

Grammar of a string literal:

string-literal → static-string-literal | interpolated-string-literal

string-literal-opening-delimiter → extended-string-literal-delimiter? "
string-literal-closing-delimiter → " extended-string-literal-delimiter?

static-string-literal → string-literal-opening-delimiter quoted-text? string-literal-closing-delimiter
static-string-literal → multiline-string-literal-opening-delimiter multiline-quoted-text? multiline-string-literal-closing-delimiter

multiline-string-literal-opening-delimiter → extended-string-literal-delimiter? """
multiline-string-literal-closing-delimiter → """ extended-string-literal-delimiter?
extended-string-literal-delimiter → # extended-string-literal-delimiter?

quoted-text → quoted-text-item quoted-text?
quoted-text-item → escaped-character
quoted-text-item → Any Unicode scalar value except ", \, U+000A, or U+000D

multiline-quoted-text → multiline-quoted-text-item multiline-quoted-text?
multiline-quoted-text-item → escaped-character
multiline-quoted-text-item → Any Unicode scalar value except \
multiline-quoted-text-item → escaped-newline

interpolated-string-literal → string-literal-opening-delimiter interpolated-text? string-literal-closing-delimiter
interpolated-string-literal → multiline-string-literal-opening-delimiter multiline-interpolated-text? multiline-string-literal-closing-delimiter

interpolated-text → interpolated-text-item interpolated-text?
interpolated-text-item → \( expression ) | quoted-text-item

multiline-interpolated-text → multiline-interpolated-text-item multiline-interpolated-text?
multiline-interpolated-text-item → \( expression ) | multiline-quoted-text-item

escape-sequence → \ extended-string-literal-delimiter
escaped-character → escape-sequence 0 | escape-sequence \ | escape-sequence t | escape-sequence n | escape-sequence r | escape-sequence " | escape-sequence '
escaped-character → escape-sequence u { unicode-scalar-digits }
unicode-scalar-digits → Between one and eight hexadecimal digits

escaped-newline → escape-sequence inline-spaces? line-break

Grammar of a regular expression literal:

regular-expression-literal → regular-expression-literal-opening-delimiter regular-expression regular-expression-literal-closing-delimiter
regular-expression → Any regular expression

regular-expression-literal-opening-delimiter → extended-regular-expression-literal-delimiter? /
regular-expression-literal-closing-delimiter → / extended-regular-expression-literal-delimiter?

extended-regular-expression-literal-delimiter → # extended-regular-expression-literal-delimiter?

Grammar of operators:

operator → operator-head operator-characters?
operator → dot-operator-head dot-operator-characters

operator-head → / | = | - | + | ! | * | % | < | > | & | | | ^ | ~ | ?
operator-head → U+00A1–U+00A7
operator-head → U+00A9 or U+00AB
operator-head → U+00AC or U+00AE
operator-head → U+00B0–U+00B1
operator-head → U+00B6, U+00BB, U+00BF, U+00D7, or U+00F7
operator-head → U+2016–U+2017
operator-head → U+2020–U+2027
operator-head → U+2030–U+203E
operator-head → U+2041–U+2053
operator-head → U+2055–U+205E
operator-head → U+2190–U+23FF
operator-head → U+2500–U+2775
operator-head → U+2794–U+2BFF
operator-head → U+2E00–U+2E7F
operator-head → U+3001–U+3003
operator-head → U+3008–U+3020
operator-head → U+3030

operator-character → operator-head
operator-character → U+0300–U+036F
operator-character → U+1DC0–U+1DFF
operator-character → U+20D0–U+20FF
operator-character → U+FE00–U+FE0F
operator-character → U+FE20–U+FE2F
operator-character → U+E0100–U+E01EF
operator-characters → operator-character operator-characters?

dot-operator-head → .
dot-operator-character → . | operator-character
dot-operator-characters → dot-operator-character dot-operator-characters?

infix-operator → operator
prefix-operator → operator
postfix-operator → operator

Types

Grammar of a type:

type → function-type
type → array-type
type → dictionary-type
type → type-identifier
type → tuple-type
type → optional-type
type → implicitly-unwrapped-optional-type
type → protocol-composition-type
type → opaque-type
type → metatype-type
type → any-type
type → self-type
type → ( type )

Grammar of a type annotation:

type-annotation → : attributes? inout? type

Grammar of a type identifier:

type-identifier → type-name generic-argument-clause? | type-name generic-argument-clause? . type-identifier
type-name → identifier

Grammar of a tuple type:

tuple-type → ( ) | ( tuple-type-element , tuple-type-element-list )
tuple-type-element-list → tuple-type-element | tuple-type-element , tuple-type-element-list
tuple-type-element → element-name type-annotation | type
element-name → identifier

Grammar of a function type:

function-type → attributes? function-type-argument-clause async? throws-clause? -> type

function-type-argument-clause → ( )
function-type-argument-clause → ( function-type-argument-list ...? )

function-type-argument-list → function-type-argument | function-type-argument , function-type-argument-list
function-type-argument → attributes? inout? type | argument-label type-annotation
argument-label → identifier

throws-clause → throws | throws ( type )

Grammar of an array type:

array-type → [ type ]

Grammar of a dictionary type:

dictionary-type → [ type : type ]

Grammar of an optional type:

optional-type → type ?

Grammar of an implicitly unwrapped optional type:

implicitly-unwrapped-optional-type → type !

Grammar of a protocol composition type:

protocol-composition-type → type-identifier & protocol-composition-continuation
protocol-composition-continuation → type-identifier | protocol-composition-type

Grammar of an opaque type:

opaque-type → some type

Grammar of a boxed protocol type:

boxed-protocol-type → any type

Grammar of a metatype type:

metatype-type → type . Type | type . Protocol

Grammar of an Any type:

any-type → Any

Grammar of a Self type:

self-type → Self

Grammar of a type inheritance clause:

type-inheritance-clause → : type-inheritance-list
type-inheritance-list → attributes? type-identifier | attributes? type-identifier , type-inheritance-list

Expressions

Grammar of an expression:

expression → try-operator? await-operator? prefix-expression infix-expressions?

Grammar of a prefix expression:

prefix-expression → prefix-operator? postfix-expression
prefix-expression → in-out-expression

Grammar of an in-out expression:

in-out-expression → & primary-expression

Grammar of a try expression:

try-operator → try | try ? | try !

Grammar of an await expression:

await-operator → await

Grammar of an infix expression:

infix-expression → infix-operator prefix-expression
infix-expression → assignment-operator try-operator? await-operator? prefix-expression
infix-expression → conditional-operator try-operator? await-operator? prefix-expression
infix-expression → type-casting-operator
infix-expressions → infix-expression infix-expressions?

Grammar of an assignment operator:

assignment-operator → =

Grammar of a conditional operator:

conditional-operator → ? expression :

Grammar of a type-casting operator:

type-casting-operator → is type
type-casting-operator → as type
type-casting-operator → as ? type
type-casting-operator → as ! type

Grammar of a primary expression:

primary-expression → identifier generic-argument-clause?
primary-expression → literal-expression
primary-expression → self-expression
primary-expression → superclass-expression
primary-expression → conditional-expression
primary-expression → closure-expression
primary-expression → parenthesized-expression
primary-expression → tuple-expression
primary-expression → implicit-member-expression
primary-expression → wildcard-expression
primary-expression → macro-expansion-expression
primary-expression → key-path-expression
primary-expression → selector-expression
primary-expression → key-path-string-expression

Grammar of a literal expression:

literal-expression → literal
literal-expression → array-literal | dictionary-literal | playground-literal

array-literal → [ array-literal-items? ]
array-literal-items → array-literal-item ,? | array-literal-item , array-literal-items
array-literal-item → expression

dictionary-literal → [ dictionary-literal-items ] | [ : ]
dictionary-literal-items → dictionary-literal-item ,? | dictionary-literal-item , dictionary-literal-items
dictionary-literal-item → expression : expression

playground-literal → #colorLiteral ( red : expression , green : expression , blue : expression , alpha : expression )
playground-literal → #fileLiteral ( resourceName : expression )
playground-literal → #imageLiteral ( resourceName : expression )

Grammar of a self expression:

self-expression → self | self-method-expression | self-subscript-expression | self-initializer-expression

self-method-expression → self . identifier
self-subscript-expression → self [ function-call-argument-list ]
self-initializer-expression → self . init

Grammar of a superclass expression:

superclass-expression → superclass-method-expression | superclass-subscript-expression | superclass-initializer-expression

superclass-method-expression → super . identifier
superclass-subscript-expression → super [ function-call-argument-list ]
superclass-initializer-expression → super . init

Grammar of a conditional expression:

conditional-expression → if-expression | switch-expression

if-expression → if condition-list { statement } if-expression-tail
if-expression-tail → else if-expression
if-expression-tail → else { statement }

switch-expression → switch expression { switch-expression-cases }
switch-expression-cases → switch-expression-case switch-expression-cases?
switch-expression-case → case-label statement
switch-expression-case → default-label statement

Grammar of a closure expression:

closure-expression → { attributes? closure-signature? statements? }

closure-signature → capture-list? closure-parameter-clause async? throws-clause? function-result? in
closure-signature → capture-list in

closure-parameter-clause → ( ) | ( closure-parameter-list ) | identifier-list
closure-parameter-list → closure-parameter | closure-parameter , closure-parameter-list
closure-parameter → closure-parameter-name type-annotation?
closure-parameter → closure-parameter-name type-annotation ...
closure-parameter-name → identifier

capture-list → [ capture-list-items ]
capture-list-items → capture-list-item | capture-list-item , capture-list-items
capture-list-item → capture-specifier? identifier
capture-list-item → capture-specifier? identifier = expression
capture-list-item → capture-specifier? self-expression
capture-specifier → weak | unowned | unowned(safe) | unowned(unsafe)

Grammar of an implicit member expression:

implicit-member-expression → . identifier
implicit-member-expression → . identifier . postfix-expression

Grammar of a parenthesized expression:

parenthesized-expression → ( expression )

Grammar of a tuple expression:

tuple-expression → ( ) | ( tuple-element , tuple-element-list )
tuple-element-list → tuple-element | tuple-element , tuple-element-list
tuple-element → expression | identifier : expression

Grammar of a wildcard expression:

wildcard-expression → _

Grammar of a macro-expansion expression:

macro-expansion-expression → # identifier generic-argument-clause? function-call-argument-clause? trailing-closures?

Grammar of a key-path expression:

key-path-expression → \ type? . key-path-components
key-path-components → key-path-component | key-path-component . key-path-components
key-path-component → identifier key-path-postfixes? | key-path-postfixes

key-path-postfixes → key-path-postfix key-path-postfixes?
key-path-postfix → ? | ! | self | [ function-call-argument-list ]

Grammar of a selector expression:

selector-expression → #selector ( expression )
selector-expression → #selector ( getter: expression )
selector-expression → #selector ( setter: expression )

Grammar of a key-path string expression:

key-path-string-expression → #keyPath ( expression )

Grammar of a postfix expression:

postfix-expression → primary-expression
postfix-expression → postfix-expression postfix-operator
postfix-expression → function-call-expression
postfix-expression → initializer-expression
postfix-expression → explicit-member-expression
postfix-expression → postfix-self-expression
postfix-expression → subscript-expression
postfix-expression → forced-value-expression
postfix-expression → optional-chaining-expression

Grammar of a function call expression:

function-call-expression → postfix-expression function-call-argument-clause
function-call-expression → postfix-expression function-call-argument-clause? trailing-closures

function-call-argument-clause → ( ) | ( function-call-argument-list )
function-call-argument-list → function-call-argument | function-call-argument , function-call-argument-list
function-call-argument → expression | identifier : expression
function-call-argument → operator | identifier : operator

trailing-closures → closure-expression labeled-trailing-closures?
labeled-trailing-closures → labeled-trailing-closure labeled-trailing-closures?
labeled-trailing-closure → identifier : closure-expression

Grammar of an initializer expression:

initializer-expression → postfix-expression . init
initializer-expression → postfix-expression . init ( argument-names )

Grammar of an explicit member expression:

explicit-member-expression → postfix-expression . decimal-digits
explicit-member-expression → postfix-expression . identifier generic-argument-clause?
explicit-member-expression → postfix-expression . identifier ( argument-names )
explicit-member-expression → postfix-expression conditional-compilation-block

argument-names → argument-name argument-names?
argument-name → identifier :

Grammar of a postfix self expression:

postfix-self-expression → postfix-expression . self

Grammar of a subscript expression:

subscript-expression → postfix-expression [ function-call-argument-list ]

Grammar of a forced-value expression:

forced-value-expression → postfix-expression !

Grammar of an optional-chaining expression:

optional-chaining-expression → postfix-expression ?

Statements

Grammar of a statement:

statement → expression ;?
statement → declaration ;?
statement → loop-statement ;?
statement → branch-statement ;?
statement → labeled-statement ;?
statement → control-transfer-statement ;?
statement → defer-statement ;?
statement → do-statement ;?
statement → compiler-control-statement
statements → statement statements?

Grammar of a loop statement:

loop-statement → for-in-statement
loop-statement → while-statement
loop-statement → repeat-while-statement

Grammar of a for-in statement:

for-in-statement → for case? pattern in expression where-clause? code-block

Grammar of a while statement:

while-statement → while condition-list code-block

condition-list → condition | condition , condition-list
condition → expression | availability-condition | case-condition | optional-binding-condition

case-condition → case pattern initializer
optional-binding-condition → let pattern initializer? | var pattern initializer?

Grammar of a repeat-while statement:

repeat-while-statement → repeat code-block while expression

Grammar of a branch statement:

branch-statement → if-statement
branch-statement → guard-statement
branch-statement → switch-statement

Grammar of an if statement:

if-statement → if condition-list code-block else-clause?
else-clause → else code-block | else if-statement

Grammar of a guard statement:

guard-statement → guard condition-list else code-block

Grammar of a switch statement:

switch-statement → switch expression { switch-cases? }
switch-cases → switch-case switch-cases?
switch-case → case-label statements
switch-case → default-label statements
switch-case → conditional-switch-case

case-label → attributes? case case-item-list :
case-item-list → pattern where-clause? | pattern where-clause? , case-item-list
default-label → attributes? default :

where-clause → where where-expression
where-expression → expression

conditional-switch-case → switch-if-directive-clause switch-elseif-directive-clauses? switch-else-directive-clause? endif-directive
switch-if-directive-clause → if-directive compilation-condition switch-cases?
switch-elseif-directive-clauses → elseif-directive-clause switch-elseif-directive-clauses?
switch-elseif-directive-clause → elseif-directive compilation-condition switch-cases?
switch-else-directive-clause → else-directive switch-cases?

Grammar of a labeled statement:

labeled-statement → statement-label loop-statement
labeled-statement → statement-label if-statement
labeled-statement → statement-label switch-statement
labeled-statement → statement-label do-statement

statement-label → label-name :
label-name → identifier

Grammar of a control transfer statement:

control-transfer-statement → break-statement
control-transfer-statement → continue-statement
control-transfer-statement → fallthrough-statement
control-transfer-statement → return-statement
control-transfer-statement → throw-statement

Grammar of a break statement:

break-statement → break label-name?

Grammar of a continue statement:

continue-statement → continue label-name?

Grammar of a fallthrough statement:

fallthrough-statement → fallthrough

Grammar of a return statement:

return-statement → return expression?

Grammar of a throw statement:

throw-statement → throw expression

Grammar of a defer statement:

defer-statement → defer code-block

Grammar of a do statement:

do-statement → do throws-clause? code-block catch-clauses?
catch-clauses → catch-clause catch-clauses?
catch-clause → catch catch-pattern-list? code-block
catch-pattern-list → catch-pattern | catch-pattern , catch-pattern-list
catch-pattern → pattern where-clause?

Grammar of a compiler control statement:

compiler-control-statement → conditional-compilation-block
compiler-control-statement → line-control-statement
compiler-control-statement → diagnostic-statement

Grammar of a conditional compilation block:

conditional-compilation-block → if-directive-clause elseif-directive-clauses? else-directive-clause? endif-directive

if-directive-clause → if-directive compilation-condition statements?
elseif-directive-clauses → elseif-directive-clause elseif-directive-clauses?
elseif-directive-clause → elseif-directive compilation-condition statements?
else-directive-clause → else-directive statements?
if-directive → #if
elseif-directive → #elseif
else-directive → #else
endif-directive → #endif

compilation-condition → platform-condition
compilation-condition → identifier
compilation-condition → boolean-literal
compilation-condition → ( compilation-condition )
compilation-condition → ! compilation-condition
compilation-condition → compilation-condition && compilation-condition
compilation-condition → compilation-condition || compilation-condition

platform-condition → os ( operating-system )
platform-condition → arch ( architecture )
platform-condition → swift ( >= swift-version ) | swift ( < swift-version )
platform-condition → compiler ( >= swift-version ) | compiler ( < swift-version )
platform-condition → canImport ( import-path )
platform-condition → targetEnvironment ( environment )

operating-system → macOS | iOS | watchOS | tvOS | visionOS | Linux | Windows
architecture → i386 | x86_64 | arm | arm64
swift-version → decimal-digits swift-version-continuation?
swift-version-continuation → . decimal-digits swift-version-continuation?
environment → simulator | macCatalyst

Grammar of a line control statement:

line-control-statement → #sourceLocation ( file: file-path , line: line-number )
line-control-statement → #sourceLocation ( )
line-number → A decimal integer greater than zero
file-path → static-string-literal

Grammar of an availability condition:

availability-condition → #available ( availability-arguments )
availability-condition → #unavailable ( availability-arguments )
availability-arguments → availability-argument | availability-argument , availability-arguments
availability-argument → platform-name platform-version
availability-argument → *

platform-name → iOS | iOSApplicationExtension
platform-name → macOS | macOSApplicationExtension
platform-name → macCatalyst | macCatalystApplicationExtension
platform-name → watchOS | watchOSApplicationExtension
platform-name → tvOS | tvOSApplicationExtension
platform-name → visionOS | visionOSApplicationExtension
platform-version → decimal-digits
platform-version → decimal-digits . decimal-digits
platform-version → decimal-digits . decimal-digits . decimal-digits

Declarations

Grammar of a declaration:

declaration → import-declaration
declaration → constant-declaration
declaration → variable-declaration
declaration → typealias-declaration
declaration → function-declaration
declaration → enum-declaration
declaration → struct-declaration
declaration → class-declaration
declaration → actor-declaration
declaration → protocol-declaration
declaration → initializer-declaration
declaration → deinitializer-declaration
declaration → extension-declaration
declaration → subscript-declaration
declaration → operator-declaration
declaration → precedence-group-declaration

Grammar of a top-level declaration:

top-level-declaration → statements?

Grammar of a code block:

code-block → { statements? }

Grammar of an import declaration:

import-declaration → attributes? import import-kind? import-path

import-kind → typealias | struct | class | enum | protocol | let | var | func
import-path → identifier | identifier . import-path

Grammar of a constant declaration:

constant-declaration → attributes? declaration-modifiers? let pattern-initializer-list

pattern-initializer-list → pattern-initializer | pattern-initializer , pattern-initializer-list
pattern-initializer → pattern initializer?
initializer → = expression

Grammar of a variable declaration:

variable-declaration → variable-declaration-head pattern-initializer-list
variable-declaration → variable-declaration-head variable-name type-annotation code-block
variable-declaration → variable-declaration-head variable-name type-annotation getter-setter-block
variable-declaration → variable-declaration-head variable-name type-annotation getter-setter-keyword-block
variable-declaration → variable-declaration-head variable-name initializer willSet-didSet-block
variable-declaration → variable-declaration-head variable-name type-annotation initializer? willSet-didSet-block

variable-declaration-head → attributes? declaration-modifiers? var
variable-name → identifier

getter-setter-block → code-block
getter-setter-block → { getter-clause setter-clause? }
getter-setter-block → { setter-clause getter-clause }
getter-clause → attributes? mutation-modifier? get code-block
setter-clause → attributes? mutation-modifier? set setter-name? code-block
setter-name → ( identifier )

getter-setter-keyword-block → { getter-keyword-clause setter-keyword-clause? }
getter-setter-keyword-block → { setter-keyword-clause getter-keyword-clause }
getter-keyword-clause → attributes? mutation-modifier? get
setter-keyword-clause → attributes? mutation-modifier? set

willSet-didSet-block → { willSet-clause didSet-clause? }
willSet-didSet-block → { didSet-clause willSet-clause? }
willSet-clause → attributes? willSet setter-name? code-block
didSet-clause → attributes? didSet setter-name? code-block

Grammar of a type alias declaration:

typealias-declaration → attributes? access-level-modifier? typealias typealias-name generic-parameter-clause? typealias-assignment
typealias-name → identifier
typealias-assignment → = type

Grammar of a function declaration:

function-declaration → function-head function-name generic-parameter-clause? function-signature generic-where-clause? function-body?

function-head → attributes? declaration-modifiers? func
function-name → identifier | operator

function-signature → parameter-clause async? throws-clause? function-result?
function-signature → parameter-clause async? rethrows function-result?
function-result → -> attributes? type
function-body → code-block

parameter-clause → ( ) | ( parameter-list )
parameter-list → parameter | parameter , parameter-list
parameter → external-parameter-name? local-parameter-name parameter-type-annotation default-argument-clause?
parameter → external-parameter-name? local-parameter-name parameter-type-annotation
parameter → external-parameter-name? local-parameter-name parameter-type-annotation ...

external-parameter-name → identifier
local-parameter-name → identifier
parameter-type-annotation → : attributes? parameter-modifier? type
parameter-modifier → inout | borrowing | consuming default-argument-clause → = expression

Grammar of an enumeration declaration:

enum-declaration → attributes? access-level-modifier? union-style-enum
enum-declaration → attributes? access-level-modifier? raw-value-style-enum

union-style-enum → indirect? enum enum-name generic-parameter-clause? type-inheritance-clause? generic-where-clause? { union-style-enum-members? }
union-style-enum-members → union-style-enum-member union-style-enum-members?
union-style-enum-member → declaration | union-style-enum-case-clause | compiler-control-statement
union-style-enum-case-clause → attributes? indirect? case union-style-enum-case-list
union-style-enum-case-list → union-style-enum-case | union-style-enum-case , union-style-enum-case-list
union-style-enum-case → enum-case-name tuple-type?
enum-name → identifier
enum-case-name → identifier

raw-value-style-enum → enum enum-name generic-parameter-clause? type-inheritance-clause generic-where-clause? { raw-value-style-enum-members }
raw-value-style-enum-members → raw-value-style-enum-member raw-value-style-enum-members?
raw-value-style-enum-member → declaration | raw-value-style-enum-case-clause | compiler-control-statement
raw-value-style-enum-case-clause → attributes? case raw-value-style-enum-case-list
raw-value-style-enum-case-list → raw-value-style-enum-case | raw-value-style-enum-case , raw-value-style-enum-case-list
raw-value-style-enum-case → enum-case-name raw-value-assignment?
raw-value-assignment → = raw-value-literal
raw-value-literal → numeric-literal | static-string-literal | boolean-literal

Grammar of a structure declaration:

struct-declaration → attributes? access-level-modifier? struct struct-name generic-parameter-clause? type-inheritance-clause? generic-where-clause? struct-body
struct-name → identifier
struct-body → { struct-members? }

struct-members → struct-member struct-members?
struct-member → declaration | compiler-control-statement

Grammar of a class declaration:

class-declaration → attributes? access-level-modifier? final? class class-name generic-parameter-clause? type-inheritance-clause? generic-where-clause? class-body
class-declaration → attributes? final access-level-modifier? class class-name generic-parameter-clause? type-inheritance-clause? generic-where-clause? class-body
class-name → identifier
class-body → { class-members? }

class-members → class-member class-members?
class-member → declaration | compiler-control-statement

Grammar of an actor declaration:

actor-declaration → attributes? access-level-modifier? actor actor-name generic-parameter-clause? type-inheritance-clause? generic-where-clause? actor-body
actor-name → identifier
actor-body → { actor-members? }

actor-members → actor-member actor-members?
actor-member → declaration | compiler-control-statement

Grammar of a protocol declaration:

protocol-declaration → attributes? access-level-modifier? protocol protocol-name type-inheritance-clause? generic-where-clause? protocol-body
protocol-name → identifier
protocol-body → { protocol-members? }

protocol-members → protocol-member protocol-members?
protocol-member → protocol-member-declaration | compiler-control-statement

protocol-member-declaration → protocol-property-declaration
protocol-member-declaration → protocol-method-declaration
protocol-member-declaration → protocol-initializer-declaration
protocol-member-declaration → protocol-subscript-declaration
protocol-member-declaration → protocol-associated-type-declaration
protocol-member-declaration → typealias-declaration

Grammar of a protocol property declaration:

protocol-property-declaration → variable-declaration-head variable-name type-annotation getter-setter-keyword-block

Grammar of a protocol method declaration:

protocol-method-declaration → function-head function-name generic-parameter-clause? function-signature generic-where-clause?

Grammar of a protocol initializer declaration:

protocol-initializer-declaration → initializer-head generic-parameter-clause? parameter-clause throws-clause? generic-where-clause?
protocol-initializer-declaration → initializer-head generic-parameter-clause? parameter-clause rethrows generic-where-clause?

Grammar of a protocol subscript declaration:

protocol-subscript-declaration → subscript-head subscript-result generic-where-clause? getter-setter-keyword-block

Grammar of a protocol associated type declaration:

protocol-associated-type-declaration → attributes? access-level-modifier? associatedtype typealias-name type-inheritance-clause? typealias-assignment? generic-where-clause?

Grammar of an initializer declaration:

initializer-declaration → initializer-head generic-parameter-clause? parameter-clause async? throws-clause? generic-where-clause? initializer-body
initializer-declaration → initializer-head generic-parameter-clause? parameter-clause async? rethrows generic-where-clause? initializer-body
initializer-head → attributes? declaration-modifiers? init
initializer-head → attributes? declaration-modifiers? init ?
initializer-head → attributes? declaration-modifiers? init !
initializer-body → code-block

Grammar of a deinitializer declaration:

deinitializer-declaration → attributes? deinit code-block

Grammar of an extension declaration:

extension-declaration → attributes? access-level-modifier? extension type-identifier type-inheritance-clause? generic-where-clause? extension-body
extension-body → { extension-members? }

extension-members → extension-member extension-members?
extension-member → declaration | compiler-control-statement

Grammar of a subscript declaration:

subscript-declaration → subscript-head subscript-result generic-where-clause? code-block
subscript-declaration → subscript-head subscript-result generic-where-clause? getter-setter-block
subscript-declaration → subscript-head subscript-result generic-where-clause? getter-setter-keyword-block
subscript-head → attributes? declaration-modifiers? subscript generic-parameter-clause? parameter-clause
subscript-result → -> attributes? type

Grammar of a macro declaration:

macro-declaration → macro-head identifier generic-parameter-clause? macro-signature macro-definition? generic-where-clause
macro-head → attributes? declaration-modifiers? macro
macro-signature → parameter-clause macro-function-signature-result?
macro-function-signature-result → -> type
macro-definition → = expression

Grammar of an operator declaration:

operator-declaration → prefix-operator-declaration | postfix-operator-declaration | infix-operator-declaration

prefix-operator-declaration → prefix operator operator
postfix-operator-declaration → postfix operator operator
infix-operator-declaration → infix operator operator infix-operator-group?

infix-operator-group → : precedence-group-name

Grammar of a precedence group declaration:

precedence-group-declaration → precedencegroup precedence-group-name { precedence-group-attributes? }

precedence-group-attributes → precedence-group-attribute precedence-group-attributes?
precedence-group-attribute → precedence-group-relation
precedence-group-attribute → precedence-group-assignment
precedence-group-attribute → precedence-group-associativity

precedence-group-relation → higherThan : precedence-group-names
precedence-group-relation → lowerThan : precedence-group-names

precedence-group-assignment → assignment : boolean-literal

precedence-group-associativity → associativity : left
precedence-group-associativity → associativity : right
precedence-group-associativity → associativity : none

precedence-group-names → precedence-group-name | precedence-group-name , precedence-group-names
precedence-group-name → identifier

Grammar of a declaration modifier:

declaration-modifier → class | convenience | dynamic | final | infix | lazy | optional | override | postfix | prefix | required | static | unowned | unowned ( safe ) | unowned ( unsafe ) | weak
declaration-modifier → access-level-modifier
declaration-modifier → mutation-modifier
declaration-modifier → actor-isolation-modifier
declaration-modifiers → declaration-modifier declaration-modifiers?

access-level-modifier → private | private ( set )
access-level-modifier → fileprivate | fileprivate ( set )
access-level-modifier → internal | internal ( set )
access-level-modifier → package | package ( set )
access-level-modifier → public | public ( set )
access-level-modifier → open | open ( set )

mutation-modifier → mutating | nonmutating

actor-isolation-modifier → nonisolated

Attributes

Grammar of an attribute:

attribute → @ attribute-name attribute-argument-clause?
attribute-name → identifier
attribute-argument-clause → ( balanced-tokens? )
attributes → attribute attributes?

balanced-tokens → balanced-token balanced-tokens?
balanced-token → ( balanced-tokens? )
balanced-token → [ balanced-tokens? ]
balanced-token → { balanced-tokens? }
balanced-token → Any identifier, keyword, literal, or operator
balanced-token → Any punctuation except (, ), [, ], {, or }

Patterns

Grammar of a pattern:

pattern → wildcard-pattern type-annotation?
pattern → identifier-pattern type-annotation?
pattern → value-binding-pattern
pattern → tuple-pattern type-annotation?
pattern → enum-case-pattern
pattern → optional-pattern
pattern → type-casting-pattern
pattern → expression-pattern

Grammar of a wildcard pattern:

wildcard-pattern → _

Grammar of an identifier pattern:

identifier-pattern → identifier

Grammar of a value-binding pattern:

value-binding-pattern → var pattern | let pattern

Grammar of a tuple pattern:

tuple-pattern → ( tuple-pattern-element-list? )
tuple-pattern-element-list → tuple-pattern-element | tuple-pattern-element , tuple-pattern-element-list
tuple-pattern-element → pattern | identifier : pattern

Grammar of an enumeration case pattern:

enum-case-pattern → type-identifier? . enum-case-name tuple-pattern?

Grammar of an optional pattern:

optional-pattern → identifier-pattern ?

Grammar of a type casting pattern:

type-casting-pattern → is-pattern | as-pattern
is-pattern → is type
as-pattern → pattern as type

Grammar of an expression pattern:

expression-pattern → expression

Generic Parameters and Arguments

Grammar of a generic parameter clause:

generic-parameter-clause → < generic-parameter-list >
generic-parameter-list → generic-parameter | generic-parameter , generic-parameter-list
generic-parameter → type-name
generic-parameter → type-name : type-identifier
generic-parameter → type-name : protocol-composition-type

generic-where-clause → where requirement-list
requirement-list → requirement | requirement , requirement-list
requirement → conformance-requirement | same-type-requirement

conformance-requirement → type-identifier : type-identifier
conformance-requirement → type-identifier : protocol-composition-type
same-type-requirement → type-identifier == type

Grammar of a generic argument clause:

generic-argument-clause → < generic-argument-list >
generic-argument-list → generic-argument | generic-argument , generic-argument-list
generic-argument → type