Unified: Local scoping followups

unified/extractor/ast_types.yml

@@ -49,6 +49,7 @@ supertypes:
  - tuple_pattern
  - constructor_pattern
  - or_pattern
+ - conditional_pattern
  - ignore_pattern
  - expr_equality_pattern
  - bulk_importing_pattern
@@ -369,7 +370,6 @@ named:
  catch_clause:
  modifier*: modifier
  pattern?: pattern
- guard?: expr
  body: block
 
  # `switch value { case pattern: body case ...: default: body }`
@@ -381,11 +381,9 @@ named:
  # A single `case ...:` (or `default:`) entry in a switch.
  # An entry with multiple `case p1, p2:` patterns uses an `or_pattern`.
  # A `default:` entry has no pattern.
- # An optional `guard` corresponds to a `where`-clause on the case.
  switch_case:
  modifier*: modifier
  pattern?: pattern
- guard?: expr
  body: block
 
  # Evaluate 'expr' and match its result against 'pattern', and return true if it matches.
@@ -446,6 +444,14 @@ named:
  modifier*: modifier
  pattern*: pattern
 
+ # A pattern that matches against a nested pattern, and subsequently checks a condition.
+ # The match is rejected if the condition does not hold.
+ # Variables bound in the nested pattern are in scope within the condition.
+ conditional_pattern:
+ modifier*: modifier
+ condition: expr
+ pattern: pattern
+
  # A pattern with an optional associated name.
  pattern_element:
  modifier*: modifier

unified/extractor/src/languages/swift/swift.rs

@@ -94,6 +94,19 @@ fn and_chain(
  .expect("control-flow statement must have at least one condition")
 }
 
+/// Return the only pattern unchanged when there is exactly one, otherwise
+/// wrap the list in an `or_pattern`.
+fn make_or_pattern(
+ ctx: &mut yeast::build::BuildCtx<'_, SwiftContext>,
+ items: Vec<yeast::Id>,
+) -> yeast::Id {
+ if items.len() == 1 {
+ items[0]
+ } else {
+ tree!((or_pattern pattern: {items}))
+ }
+}
+
 /// Translate a multi-part identifier (for example `Foo.Bar.Baz`) into a
 /// `member_access_expr` chain rooted at a `name_expr` over the first
 /// part. Panics on an empty input because the grammar's `_+` quantifier
@@ -746,22 +759,17 @@ fn translation_rules() -> Vec<Rule<SwiftContext>> {
  rule!(
  (switchCase label: (switchCaseLabel caseItems: _* @items) statements: _* @body)
  =>
- switch_case {
- let pattern = if items.len() == 1 {
- items[0]
- } else {
- tree!((or_pattern pattern: {items}))
- };
- tree!((switch_case pattern: {pattern} body: (block stmt: {body})))
- }
+ (switch_case
+ pattern: {make_or_pattern(&mut ctx, items)}
+ body: (block stmt: {body}))
  ),
  rule!(
  (switchCase label: (switchDefaultLabel) statements: _* @body)
  =>
  (switch_case body: (block stmt: {body}))
  ),
- // A single case item unwraps to its pattern (used as an `or_pattern`
-// element).
+ // A single case item unwraps to its pattern, possibly boxed in conditional_pattern
+rule!((switchCaseItem pattern: @p whereClause: (whereClause condition: @cond)) => (conditional_pattern pattern: { p } condition: {cond})),
  rule!((switchCaseItem pattern: @p) => pattern { p }),
  // A pattern-matching condition (`if case let x = e`, `if case .foo(let x)
  // = e`) becomes a `pattern_guard_expr`: the matched pattern and the
@@ -877,17 +885,24 @@ fn translation_rules() -> Vec<Rule<SwiftContext>> {
  body: {body}
  catch_clause: {catches})
  ),
- // Catch block with bound identifier; optional where-clause guard.
+ rule!(
+ (catchItem pattern: @pattern whereClause: (whereClause condition: @guard))
+ =>
+ (conditional_pattern pattern: {pattern} condition: {guard})
+ ),
+ rule!(
+ (catchItem pattern: @pattern)
+ =>
+ pattern {pattern}
+ ),
+ // Catch block with one or more patterns (which have been translated by the catchItem rules)
  rule!(
  (catchClause
- catchItems: (catchItem
- pattern: @pattern
- whereClause: (whereClause condition: @guard)?)
+ catchItems: _+ @patterns
  body: @body)
  =>
  (catch_clause
- pattern: {pattern}
- guard: {guard}
+ pattern: {make_or_pattern(&mut ctx, patterns)}
  body: {body})
  ),
  // Catch block without error binding

unified/extractor/tests/corpus/swift/control-flow/switch-case-item-where-clauses.output

@@ -0,0 +1,222 @@
+switch n {
+case let x where x > 0:
+ print("positive")
+case let y where y < 0, 0:
+ print("non-positive")
+default:
+ print("other")
+}
+
+---
+
+sourceFile
+ endOfFileToken: endOfFile
+ statements:
+ codeBlockItem
+ item:
+ expressionStmt
+ expression:
+ switchExpr
+ leftBrace: {
+ rightBrace: }
+ cases:
+ switchCase
+ label:
+ switchCaseLabel
+ colon: :
+ caseKeyword: case
+ caseItems:
+ switchCaseItem
+ pattern:
+ valueBindingPattern
+ pattern:
+ identifierPattern
+ identifier: identifier "x"
+ bindingSpecifier: let
+ whereClause:
+ whereClause
+ condition:
+ infixOperatorExpr
+ operator:
+ binaryOperatorExpr
+ operator: binaryOperator ">"
+ leftOperand:
+ declReferenceExpr
+ baseName: identifier "x"
+ rightOperand:
+ integerLiteralExpr
+ literal: integerLiteral "0"
+ whereKeyword: where
+ statements:
+ codeBlockItem
+ item:
+ functionCallExpr
+ leftParen: (
+ rightParen: )
+ arguments:
+ labeledExpr
+ expression:
+ stringLiteralExpr
+ closingQuote: "
+ openingQuote: "
+ segments:
+ stringSegment
+ content: stringSegment "positive"
+ additionalTrailingClosures:
+ calledExpression:
+ declReferenceExpr
+ baseName: identifier "print"
+ switchCase
+ label:
+ switchCaseLabel
+ colon: :
+ caseKeyword: case
+ caseItems:
+ switchCaseItem
+ trailingComma: ,
+ pattern:
+ valueBindingPattern
+ pattern:
+ identifierPattern
+ identifier: identifier "y"
+ bindingSpecifier: let
+ whereClause:
+ whereClause
+ condition:
+ infixOperatorExpr
+ operator:
+ binaryOperatorExpr
+ operator: binaryOperator "<"
+ leftOperand:
+ declReferenceExpr
+ baseName: identifier "y"
+ rightOperand:
+ integerLiteralExpr
+ literal: integerLiteral "0"
+ whereKeyword: where
+ switchCaseItem
+ pattern:
+ expressionPattern
+ expression:
+ integerLiteralExpr
+ literal: integerLiteral "0"
+ statements:
+ codeBlockItem
+ item:
+ functionCallExpr
+ leftParen: (
+ rightParen: )
+ arguments:
+ labeledExpr
+ expression:
+ stringLiteralExpr
+ closingQuote: "
+ openingQuote: "
+ segments:
+ stringSegment
+ content: stringSegment "non-positive"
+ additionalTrailingClosures:
+ calledExpression:
+ declReferenceExpr
+ baseName: identifier "print"
+ switchCase
+ label:
+ switchDefaultLabel
+ colon: :
+ defaultKeyword: default
+ statements:
+ codeBlockItem
+ item:
+ functionCallExpr
+ leftParen: (
+ rightParen: )
+ arguments:
+ labeledExpr
+ expression:
+ stringLiteralExpr
+ closingQuote: "
+ openingQuote: "
+ segments:
+ stringSegment
+ content: stringSegment "other"
+ additionalTrailingClosures:
+ calledExpression:
+ declReferenceExpr
+ baseName: identifier "print"
+ subject:
+ declReferenceExpr
+ baseName: identifier "n"
+ switchKeyword: switch
+
+---
+
+top_level
+ body:
+ block
+ stmt:
+ switch_expr
+ value:
+ name_expr
+ identifier: identifier "n"
+ case:
+ switch_case
+ pattern:
+ conditional_pattern
+ condition:
+ binary_expr
+ left:
+ name_expr
+ identifier: identifier "x"
+ operator: infix_operator ">"
+ right: int_literal "0"
+ pattern:
+ name_pattern
+ identifier: identifier "x"
+ body:
+ block
+ stmt:
+ call_expr
+ callee:
+ name_expr
+ identifier: identifier "print"
+ argument:
+ argument
+ value: string_literal "\"positive\""
+ switch_case
+ pattern:
+ or_pattern
+ pattern:
+ conditional_pattern
+ condition:
+ binary_expr
+ left:
+ name_expr
+ identifier: identifier "y"
+ operator: infix_operator "<"
+ right: int_literal "0"
+ pattern:
+ name_pattern
+ identifier: identifier "y"
+ expr_equality_pattern
+ expr: int_literal "0"
+ body:
+ block
+ stmt:
+ call_expr
+ callee:
+ name_expr
+ identifier: identifier "print"
+ argument:
+ argument
+ value: string_literal "\"non-positive\""
+ switch_case
+ body:
+ block
+ stmt:
+ call_expr
+ callee:
+ name_expr
+ identifier: identifier "print"
+ argument:
+ argument
+ value: string_literal "\"other\""

unified/extractor/tests/corpus/swift/control-flow/switch-case-item-where-clauses.swift

@@ -0,0 +1,8 @@
+switch n {
+case let x where x > 0:
+ print("positive")
+case let y where y < 0, 0:
+ print("non-positive")
+default:
+ print("other")
+}