Merge pull request #22718 from github/unified/swift-optional-binding-condition

Unified: Swift optional binding condition

Author: paldepind

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

@@ -873,13 +873,13 @@ fn translation_rules() -> Vec<Rule<SwiftContext>> {
             =>
             (pattern_guard_expr pattern: {pat} value: {val})
         ),
-        // Optional binding (`if let x = foo`, or shorthand `if let x`) desugars
-        // to a `pattern_guard_expr` matching `Optional.some(x)`. The initialized
-        // form is matched first.
+        // Optional binding conditions with an initializer (the `let p = y` in
+        // `if let p = y { ... }`). We translate this to a `pattern_guard_expr`
+        // matching `Optional.some(p)`.
         rule!(
             (optionalBindingCondition
                 bindingSpecifier: @@spec
-                pattern: (identifierPattern identifier: @@name)
+                pattern: @pattern
                 initializer: (initializerClause value: @val))
             =>
             (pattern_guard_expr
@@ -888,8 +888,11 @@ fn translation_rules() -> Vec<Rule<SwiftContext>> {
                     callee: (member_access_expr base: (identifier "Optional") member_name_node: (identifier "some"))
                     argument: (argument value: (expr_pattern
                         modifier: (modifier #{spec})
-                        expr: (identifier #{name})))))
+                        expr: {pattern}))))
         ),
+        // Optional binding conditions in shorthand form, that is, _without_ an
+        // initializer (the `let p` in `if let p { ... }`). In this case the
+        // pattern is always an identifier.
         rule!(
             (optionalBindingCondition
                 bindingSpecifier: @@spec

unified/extractor/tests/corpus/swift/control-flow/guard-let-pattern.output

@@ -0,0 +1,86 @@
+guard let (call, thread) = optional else {
+  return
+}
+
+---
+
+sourceFile
+  endOfFileToken: endOfFile
+  statements:
+    codeBlockItem
+      item:
+        guardStmt
+          body:
+            codeBlock
+              leftBrace: {
+              rightBrace: }
+              statements:
+                codeBlockItem
+                  item:
+                    returnStmt
+                      returnKeyword: return
+          conditions:
+            conditionElement
+              condition:
+                optionalBindingCondition
+                  initializer:
+                    initializerClause
+                      equal: =
+                      value:
+                        declReferenceExpr
+                          baseName: identifier "optional"
+                  pattern:
+                    expressionPattern
+                      expression:
+                        tupleExpr
+                          leftParen: (
+                          rightParen: )
+                          elements:
+                            labeledExpr
+                              expression:
+                                patternExpr
+                                  pattern:
+                                    identifierPattern
+                                      identifier: identifier "call"
+                              trailingComma: ,
+                            labeledExpr
+                              expression:
+                                patternExpr
+                                  pattern:
+                                    identifierPattern
+                                      identifier: identifier "thread"
+                  bindingSpecifier: let
+          elseKeyword: else
+          guardKeyword: guard
+
+---
+
+top_level source="⟨body⟩"
+  body:
+    block source="⟨stmt⟩"
+      stmt:
+        guard_if_stmt source="guard ⟨condition⟩ else ⟨else⟩"
+          condition:
+            pattern_guard_expr source="⟨pattern⟩ = ⟨value⟩"
+              pattern:
+                call_expr source="⟨argument⟩"
+                  callee:
+                    member_access_expr source=""
+                      base: identifier "Optional" source=""
+                      member_name_node: identifier "some" source=""
+                  argument:
+                    argument source="⟨value⟩"
+                      value:
+                        expr_pattern source="⟨modifier⟩ ⟨expr⟩"
+                          modifier: modifier "let" source="let"
+                          expr:
+                            tuple_expr source="(⟨element⟩, ⟨element⟩)"
+                              element:
+                                argument source="⟨value⟩"
+                                  value: identifier "call" source="call"
+                                argument source="⟨value⟩"
+                                  value: identifier "thread" source="thread"
+              value: identifier "optional" source="optional"
+          else:
+            block source="{\n  ⟨stmt⟩\n}"
+              stmt: return_expr "return" source="return"

unified/extractor/tests/corpus/swift/control-flow/guard-let-pattern.swift

@@ -0,0 +1,3 @@
+guard let (call, thread) = optional else {
+  return
+}

unified/extractor/tests/corpus/swift/control-flow/guard-let-shorthand.output

@@ -0,0 +1,55 @@
+guard let value else { return }
+
+---
+
+sourceFile
+  endOfFileToken: endOfFile
+  statements:
+    codeBlockItem
+      item:
+        guardStmt
+          body:
+            codeBlock
+              leftBrace: {
+              rightBrace: }
+              statements:
+                codeBlockItem
+                  item:
+                    returnStmt
+                      returnKeyword: return
+          conditions:
+            conditionElement
+              condition:
+                optionalBindingCondition
+                  pattern:
+                    identifierPattern
+                      identifier: identifier "value"
+                  bindingSpecifier: let
+          elseKeyword: else
+          guardKeyword: guard
+
+---
+
+top_level source="⟨body⟩"
+  body:
+    block source="⟨stmt⟩"
+      stmt:
+        guard_if_stmt source="guard ⟨condition⟩ else ⟨else⟩"
+          condition:
+            pattern_guard_expr source="⟨pattern⟩⟨value⟩"
+              pattern:
+                call_expr source="⟨argument⟩"
+                  callee:
+                    member_access_expr source=""
+                      base: identifier "Optional" source=""
+                      member_name_node: identifier "some" source=""
+                  argument:
+                    argument source="⟨value⟩"
+                      value:
+                        expr_pattern source="⟨modifier⟩ ⟨expr⟩"
+                          modifier: modifier "let" source="let"
+                          expr: identifier "value" source="value"
+              value: identifier "value" source="value"
+          else:
+            block source="{ ⟨stmt⟩ }"
+              stmt: return_expr "return" source="return"

unified/extractor/tests/corpus/swift/control-flow/guard-let-shorthand.swift

@@ -0,0 +1 @@
+guard let value else { return }