Mihaela Mihaljevic
189190e571
Paired with mihaelamj/cupertino#1093 which splits swift-org and swift-book into independent fetchable sources. Migration: - cupertino-docs/swift-org/swift-book/ → cupertino-docs/swift-book/ - swift-book gets its own top-level corpus dir matching defaultOutputDirKey = .swiftBook - swift-org's metadata.json updated for the slimmer crawl Content refresh: - New cache snapshots from a forced fetch (8 minute crawl). All 43 topics now carry latest Apple content. Previously-orphan summaryofthegrammar + revisionhistory have fresh cache snapshots. swift-book.db consumers (cupertino save --source swift-book --clear) read from cupertino-docs/swift-book/ now, not from swift-org/swift-book/.
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| https://docs.swift.org/swift-book/documentation/the-swift-programming-language/summaryofthegrammar/ | 2025-11-21T21:38:29Z |
Summary of the Grammar | Documentation
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 → decimal-digit 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