Add support for lifetime dependence in parameter position

Author: meg-gupta

SwiftCompilerSources/Sources/SIL/FunctionConvention.swift

@@ -77,13 +77,18 @@ public struct FunctionConvention : CustomStringConvertible {
   /// Collection of LifetimeDependenceConvention indexed on the
   /// function parameter.
   public var resultDependencies: ResultDependencies? {
-    let deps = bridgedFunctionType.SILFunctionType_getLifetimeDependenceInfo()
-    if deps.empty() {
-      return nil
+    let bridgedDependencies = bridgedFunctionType.SILFunctionType_getLifetimeDependencies()
+    let dependencies = LifetimeDependencies(bridged: bridgedDependencies)
+    let targetIndex = parameters.count
+
+    for dependence in dependencies {
+      if dependence.getTargetIndex() == targetIndex {
+        return ResultDependencies(bridged: dependence,
+                                  parameterCount: parameters.count,
+                                  hasSelfParameter: hasSelfParameter)
+      }
     }
-    return ResultDependencies(bridged: deps,
-                                         parameterCount: parameters.count,
-                                         hasSelfParameter: hasSelfParameter)
+    return nil
   }
 
   public var description: String {
@@ -242,6 +247,26 @@ public enum LifetimeDependenceConvention : CustomStringConvertible {
   }
 }
 
+extension FunctionConvention {
+  struct LifetimeDependencies : Collection {
+    let bridged: BridgedLifetimeDependenceInfoArray
+
+    var startIndex: Int { 0 }
+
+    var endIndex: Int { bridged.count() }
+
+    func index(after index: Int) -> Int {
+      return index + 1
+    }
+    // Create a Swift LifetimeDependenceInfo for BridgedLifetimeDependenceInfo if this method needs
+    // to be exposed outside FunctionConvention.
+    // That will likely need bridging IndexSubset to Swift.
+    subscript(_ index: Int) -> BridgedLifetimeDependenceInfo {
+      return bridged.at(index)
+    }
+  }
+}
+
 extension FunctionConvention {
   /// Collection of LifetimeDependenceConvention? that parallels parameters.
   public struct ResultDependencies : Collection, CustomStringConvertible {

include/swift/AST/Decl.h

@@ -7482,7 +7482,8 @@ class AbstractFunctionDecl : public GenericContext, public ValueDecl {
 
   /// Add the given derivative function configuration.
   void addDerivativeFunctionConfiguration(const AutoDiffConfig &config);
-  std::optional<LifetimeDependenceInfo> getLifetimeDependenceInfo() const;
+  std::optional<llvm::ArrayRef<LifetimeDependenceInfo>>
+  getLifetimeDependencies() const;
 
 protected:
   // If a function has a body at all, we have either a parsed body AST node or

include/swift/AST/DiagnosticsSema.def

@@ -7981,8 +7981,8 @@ ERROR(lifetime_dependence_invalid_self_ownership, none,
 ERROR(lifetime_dependence_only_on_function_method_init_result, none,
       "lifetime dependence specifiers may only be used on result of "
        "functions, methods, initializers", ())
-ERROR(lifetime_dependence_invalid_return_type, none,
-      "lifetime dependence can only be specified on ~Escapable results", ())
+ERROR(lifetime_dependence_invalid_type, none,
+      "lifetime dependence can only be specified on ~Escapable types", ())
 ERROR(lifetime_dependence_cannot_infer_ambiguous_candidate, none,
       "cannot infer lifetime dependence %0, multiple parameters qualifiy as a candidate", (StringRef))
  ERROR(lifetime_dependence_cannot_infer_no_candidates, none,