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Compactify syntax diagrams #1818

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7d720ec
Compactify syntax diagrams
lukaslueg May 8, 2025
eb020fc
Add missing bypass on `BorrowExpression`
traviscross May 12, 2025
5a4d768
Rework grammar compactions
traviscross May 12, 2025
13e0083
Add other grammar compactions
traviscross May 12, 2025
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7 changes: 4 additions & 3 deletions src/attributes.md
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Expand Up @@ -116,9 +116,10 @@ attributes]. It has the following grammar:
r[attributes.meta.syntax]
```grammar,attributes
MetaItem ->
SimplePath
| SimplePath `=` Expression
| SimplePath `(` MetaSeq? `)`
SimplePath (
`=` Expression
| `(` MetaSeq? `)`
)?

MetaSeq ->
MetaItemInner ( `,` MetaItemInner )* `,`?
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3 changes: 1 addition & 2 deletions src/comments.md
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Expand Up @@ -4,8 +4,7 @@ r[comments]
r[comments.syntax]
```grammar,lexer
@root LINE_COMMENT ->
`//` (~[`/` `!` LF] | `//`) ~LF*
| `//`
`//` ( ( ~[`/` `!` LF] | `//` ) ~LF* )?

BLOCK_COMMENT ->
`/*`
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6 changes: 4 additions & 2 deletions src/expressions/array-expr.md
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Expand Up @@ -8,8 +8,10 @@ r[expr.array.syntax]
ArrayExpression -> `[` ArrayElements? `]`

ArrayElements ->
Expression ( `,` Expression )* `,`?
| Expression `;` Expression
Expression (
( `,` Expression )* `,`?
| `;` Expression
)
```

r[expr.array.constructor]
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3 changes: 1 addition & 2 deletions src/expressions/block-expr.md
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Expand Up @@ -10,8 +10,7 @@ BlockExpression ->
`}`

Statements ->
Statement+
| Statement+ ExpressionWithoutBlock
Statement+ ExpressionWithoutBlock?
| ExpressionWithoutBlock
```

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50 changes: 16 additions & 34 deletions src/expressions/operator-expr.md
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Expand Up @@ -58,10 +58,9 @@ r[expr.operator.borrow]
r[expr.operator.borrow.syntax]
```grammar,expressions
BorrowExpression ->
(`&`|`&&`) Expression
| (`&`|`&&`) `mut` Expression
| (`&`|`&&`) `raw` `const` Expression
| (`&`|`&&`) `raw` `mut` Expression
( `&` | `&&` )
( `mut` | `raw` ( `const` | `mut` ) )?
Expression
```

r[expr.operator.borrow.intro]
Expand Down Expand Up @@ -257,8 +256,7 @@ r[expr.negate]
r[expr.negate.syntax]
```grammar,expressions
NegationExpression ->
`-` Expression
| `!` Expression
( `-` | `!`) Expression
```

r[expr.negate.intro]
Expand Down Expand Up @@ -291,16 +289,9 @@ r[expr.arith-logic]
r[expr.arith-logic.syntax]
```grammar,expressions
ArithmeticOrLogicalExpression ->
Expression `+` Expression
| Expression `-` Expression
| Expression `*` Expression
| Expression `/` Expression
| Expression `%` Expression
| Expression `&` Expression
| Expression `|` Expression
| Expression `^` Expression
| Expression `<<` Expression
| Expression `>>` Expression
Expression (
`+` | `-` | `*` | `/` | `%` | `&` | `|` | `^` | `<<` | `>>`
) Expression
```

r[expr.arith-logic.intro]
Expand Down Expand Up @@ -354,12 +345,9 @@ r[expr.cmp]
r[expr.cmp.syntax]
```grammar,expressions
ComparisonExpression ->
Expression `==` Expression
| Expression `!=` Expression
| Expression `>` Expression
| Expression `<` Expression
| Expression `>=` Expression
| Expression `<=` Expression
Expression (
`==` | `!=` | `>` | `<` | `>=` | `<=`
) Expression
```

r[expr.cmp.intro]
Expand Down Expand Up @@ -413,8 +401,7 @@ r[expr.bool-logic]
r[expr.bool-logic.syntax]
```grammar,expressions
LazyBooleanExpression ->
Expression `||` Expression
| Expression `&&` Expression
Expression (`||` | `&&`) Expression
```

r[expr.bool-logic.intro]
Expand Down Expand Up @@ -809,16 +796,11 @@ r[expr.compound-assign]
r[expr.compound-assign.syntax]
```grammar,expressions
CompoundAssignmentExpression ->
Expression `+=` Expression
| Expression `-=` Expression
| Expression `*=` Expression
| Expression `/=` Expression
| Expression `%=` Expression
| Expression `&=` Expression
| Expression `|=` Expression
| Expression `^=` Expression
| Expression `<<=` Expression
| Expression `>>=` Expression
Expression (
`+=` | `-=` | `*=` | `/=` | `%=`
| `&=` | `|=` | `^=`
| `<<=` | `>>=`
) Expression
```

r[expr.compound-assign.intro]
Expand Down
19 changes: 10 additions & 9 deletions src/inline-assembly.md
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Expand Up @@ -73,20 +73,21 @@ AsmOption ->
| `att_syntax`
| `raw`

RegOperand -> (ParamName `=`)?
(
DirSpec `(` RegSpec `)` Expression
| DualDirSpec `(` RegSpec `)` DualDirSpecExpression
| `sym` PathExpression
| `const` Expression
| `label` `{` Statements? `}`
RegOperand ->
(ParamName `=`)? (
(
DirSpec `(` RegSpec `)`
| `const`
) Expression
| DualDirSpec `(` RegSpec `)` DualDirSpecExpression
| `sym` PathExpression
| `label` `{` Statements? `}`
Comment on lines -76 to +84
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@traviscross traviscross May 12, 2025 •
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Here's an example of one that I debated on for awhile, in terms of whether the transformation was worth it. The question I asked myself was whether transforming it in this way added insight.

In the end, I decided I think it does actually. E.g., we need to decide on what syntax to use for injecting constant pointers -- e.g. whether const or sym is better for that -- and in that context, syntactically, it is interesting that Expression shares both const and e.g. in(<reg>) as common prefixes, but not sym.

)

ParamName -> IDENTIFIER_OR_KEYWORD | RAW_IDENTIFIER

DualDirSpecExpression ->
Expression
| Expression `=>` Expression
Expression ( `=>` Expression )?

RegSpec -> RegisterClass | ExplicitRegister

Expand Down
5 changes: 2 additions & 3 deletions src/items/external-blocks.md
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Expand Up @@ -11,9 +11,8 @@ ExternBlock ->

ExternalItem ->
OuterAttribute* (
MacroInvocationSemi
| Visibility? StaticItem
| Visibility? Function
Visibility? ( StaticItem | Function )
| MacroInvocationSemi
)
```

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8 changes: 5 additions & 3 deletions src/items/functions.md
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Expand Up @@ -16,15 +16,17 @@ ItemSafety -> `safe`[^extern-safe] | `unsafe`
Abi -> STRING_LITERAL | RAW_STRING_LITERAL

FunctionParameters ->
SelfParam `,`?
| (SelfParam `,`)? FunctionParam (`,` FunctionParam)* `,`?
SelfParam ( `,` FunctionParams? )?
| FunctionParams

SelfParam -> OuterAttribute* ( ShorthandSelf | TypedSelf )

ShorthandSelf -> (`&` | `&` Lifetime)? `mut`? `self`
ShorthandSelf -> ( `&` Lifetime? )? `mut`? `self`

TypedSelf -> `mut`? `self` `:` Type

FunctionParams -> FunctionParam ( `,` FunctionParam )* `,`?

FunctionParam -> OuterAttribute* ( FunctionParamPattern | `...` | Type[^fn-param-2015] )

FunctionParamPattern -> PatternNoTopAlt `:` ( Type | `...` )
Expand Down
9 changes: 4 additions & 5 deletions src/items/modules.md
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Expand Up @@ -4,11 +4,10 @@ r[items.mod]
r[items.mod.syntax]
```grammar,items
Module ->
`unsafe`? `mod` IDENTIFIER `;`
| `unsafe`? `mod` IDENTIFIER `{`
InnerAttribute*
Item*
`}`
`unsafe`? `mod` IDENTIFIER (
`{` InnerAttribute* Item* `}`
| `;`
)
```

r[items.mod.intro]
Expand Down
6 changes: 4 additions & 2 deletions src/items/use-declarations.md
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Expand Up @@ -6,8 +6,10 @@ r[items.use.syntax]
UseDeclaration -> `use` UseTree `;`

UseTree ->
(SimplePath? `::`)? `*`
| (SimplePath? `::`)? `{` (UseTree ( `,` UseTree )* `,`?)? `}`
( SimplePath? `::` )? (
`{` ( UseTree ( `,` UseTree )* `,`? )? `}`
| `*`
)
| SimplePath ( `as` ( IDENTIFIER | `_` ) )?
```

Expand Down
13 changes: 9 additions & 4 deletions src/macros-by-example.md
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Expand Up @@ -7,8 +7,10 @@ MacroRulesDefinition ->
`macro_rules` `!` IDENTIFIER MacroRulesDef

MacroRulesDef ->
`(` MacroRules `)` `;`
| `[` MacroRules `]` `;`
(
`(` MacroRules `)`
| `[` MacroRules `]`
) `;`
| `{` MacroRules `}`

MacroRules ->
Expand All @@ -25,8 +27,11 @@ MacroMatcher ->
MacroMatch ->
Token _except `$` and [delimiters][lex.token.delim]_
| MacroMatcher
| `$` ( IDENTIFIER_OR_KEYWORD _except `crate`_ | RAW_IDENTIFIER | `_` ) `:` MacroFragSpec
| `$` `(` MacroMatch+ `)` MacroRepSep? MacroRepOp
| `$` (
( IDENTIFIER_OR_KEYWORD _except `crate`_ | RAW_IDENTIFIER | `_` )
`:` MacroFragSpec
| `(` MacroMatch+ `)` MacroRepSep? MacroRepOp
)

MacroFragSpec ->
`block` | `expr` | `expr_2021` | `ident` | `item` | `lifetime` | `literal`
Expand Down
10 changes: 7 additions & 3 deletions src/macros.md
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Expand Up @@ -29,9 +29,13 @@ TokenTree ->
Token _except [delimiters][lex.token.delim]_ | DelimTokenTree

MacroInvocationSemi ->
SimplePath `!` `(` TokenTree* `)` `;`
| SimplePath `!` `[` TokenTree* `]` `;`
| SimplePath `!` `{` TokenTree* `}`
SimplePath `!` (
(
`(` TokenTree* `)`
| `[` TokenTree* `]`
) `;`
| `{` TokenTree* `}`
)
```

r[macro.invocation.intro]
Expand Down
6 changes: 2 additions & 4 deletions src/paths.md
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Expand Up @@ -54,16 +54,14 @@ PathIdentSegment ->
IDENTIFIER | `super` | `self` | `Self` | `crate` | `$crate`

GenericArgs ->
`<` `>`
| `<` ( GenericArg `,` )* GenericArg `,`? `>`
`<` ( GenericArg ( `,` GenericArg )* `,`? )? `>`

GenericArg ->
Lifetime | Type | GenericArgsConst | GenericArgsBinding | GenericArgsBounds

GenericArgsConst ->
BlockExpression
| LiteralExpression
| `-` LiteralExpression
| `-`? LiteralExpression
| SimplePathSegment

GenericArgsBinding ->
Expand Down
14 changes: 5 additions & 9 deletions src/patterns.md
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Expand Up @@ -149,8 +149,7 @@ LiteralPattern ->
| RAW_BYTE_STRING_LITERAL
| C_STRING_LITERAL
| RAW_C_STRING_LITERAL
| `-`? INTEGER_LITERAL
| `-`? FLOAT_LITERAL
| `-`? ( INTEGER_LITERAL | FLOAT_LITERAL )
```

r[patterns.literal.intro]
Expand Down Expand Up @@ -499,8 +498,7 @@ ObsoleteRangePattern ->
RangePatternBound ->
CHAR_LITERAL
| BYTE_LITERAL
| `-`? INTEGER_LITERAL
| `-`? FLOAT_LITERAL
| `-`? ( INTEGER_LITERAL | FLOAT_LITERAL )
| PathExpression
```

Expand Down Expand Up @@ -708,7 +706,7 @@ StructPattern ->
`}`

StructPatternElements ->
StructPatternFields (`,` | `,` StructPatternEtCetera)?
StructPatternFields ( `,` StructPatternEtCetera? )?
| StructPatternEtCetera

StructPatternFields ->
Expand All @@ -717,8 +715,7 @@ StructPatternFields ->
StructPatternField ->
OuterAttribute*
(
TUPLE_INDEX `:` Pattern
| IDENTIFIER `:` Pattern
( TUPLE_INDEX | IDENTIFIER ) `:` Pattern
| `ref`? `mut`? IDENTIFIER
)

Expand Down Expand Up @@ -837,9 +834,8 @@ r[patterns.tuple.syntax]
TuplePattern -> `(` TuplePatternItems? `)`

TuplePatternItems ->
Pattern `,`
Pattern ( `,` | ( `,` Pattern )+ `,`? )
| RestPattern
| Pattern (`,` Pattern)+ `,`?
```

r[patterns.tuple.intro]
Expand Down
7 changes: 5 additions & 2 deletions src/statements.md
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Expand Up @@ -61,8 +61,11 @@ r[statement.let.syntax]
LetStatement ->
OuterAttribute* `let` PatternNoTopAlt ( `:` Type )?
(
`=` Expression
| `=` Expression _except [LazyBooleanExpression] or end with a `}`_ `else` BlockExpression
`=` (
Expression _except [LazyBooleanExpression] or end with a `}`_
`else` BlockExpression
| Expression
)
)? `;`
```

Expand Down
15 changes: 10 additions & 5 deletions src/tokens.md
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Expand Up @@ -657,9 +657,11 @@ r[lex.token.literal.float]
r[lex.token.literal.float.syntax]
```grammar,lexer
FLOAT_LITERAL ->
DEC_LITERAL `.` _not immediately followed by `.`, `_` or an XID_Start character_
| DEC_LITERAL `.` DEC_LITERAL SUFFIX_NO_E?
| DEC_LITERAL (`.` DEC_LITERAL)? FLOAT_EXPONENT SUFFIX?
DEC_LITERAL (
`.` _not immediately followed by `.`, `_` or an XID_Start character_
| `.` DEC_LITERAL ( SUFFIX_NO_E? | FLOAT_EXPONENT SUFFIX? )
| FLOAT_EXPONENT SUFFIX?
)

FLOAT_EXPONENT ->
(`e`|`E`) (`+`|`-`)? (DEC_DIGIT|`_`)* DEC_DIGIT (DEC_DIGIT|`_`)*
Expand Down Expand Up @@ -714,8 +716,11 @@ r[lex.token.literal.reserved.syntax]
RESERVED_NUMBER ->
BIN_LITERAL [`2`-`9`]
| OCT_LITERAL [`8`-`9`]
| ( BIN_LITERAL | OCT_LITERAL | HEX_LITERAL ) `.` _not immediately followed by `.`, `_` or an XID_Start character_
| ( BIN_LITERAL | OCT_LITERAL ) (`e`|`E`)
| ( BIN_LITERAL | OCT_LITERAL ) (
`.` _not immediately followed by `.`, `_` or an XID_Start character_
| (`e`|`E`)
)
| HEX_LITERAL `.` _not immediately followed by `.`, `_` or an XID_Start character_
| `0b` `_`* <end of input or not BIN_DIGIT>
| `0o` `_`* <end of input or not OCT_DIGIT>
| `0x` `_`* <end of input or not HEX_DIGIT>
Expand Down
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