[ASTPrinter] Escape @_lifetime arguments when needed

rdar://159992995

Author: hnrklssn

lib/AST/LifetimeDependence.cpp

@@ -12,6 +12,7 @@
 
 #include "swift/AST/LifetimeDependence.h"
 #include "swift/AST/ASTContext.h"
+#include "swift/AST/ASTPrinter.h"
 #include "swift/AST/Builtins.h"
 #include "swift/AST/ConformanceLookup.h"
 #include "swift/AST/Decl.h"
@@ -30,8 +31,14 @@ namespace swift {
 
 std::string LifetimeDescriptor::getString() const {
   switch (kind) {
-  case DescriptorKind::Named:
+  case DescriptorKind::Named: {
+    bool shouldEscape =
+        escapeIdentifierInContext(getName(), PrintNameContext::Normal);
+    if (shouldEscape) {
+      return ("`" + getName().str() + "`").str();
+    }
     return getName().str().str();
+  }
   case DescriptorKind::Ordered:
     return std::to_string(getIndex());
   case DescriptorKind::Self:

test/IDE/print_lifetime_attr.swift

@@ -24,6 +24,14 @@ public func barFunc(_ bar: inout S) -> S {
 @_lifetime(`func`: copy `func`)
 public func funcFunc(func: inout S) {}
 
+public struct T : ~Escapable {
+    let s: S
+    @_lifetime(borrow self)
+    func selfFunc() -> S { return s }
+    @_lifetime(borrow `self`)
+    func selfFunc2(`self`: S) -> S { return `self` }
+}
+
 //--- interface.txt.expected
 
 public struct S : ~Escapable {
@@ -35,5 +43,16 @@ public struct S : ~Escapable {
 public func fooFunc(_ foo: inout S)
 @_lifetime(&bar)
 public func barFunc(_ bar: inout S) -> S
-@_lifetime(func: copy func)
+@_lifetime(`func`: copy `func`)
 public func funcFunc(func: inout S)
+
+public struct T : ~Escapable {
+
+    internal let s: S
+
+    @_lifetime(borrow self)
+    internal func selfFunc() -> S
+
+    @_lifetime(borrow `self`)
+    internal func selfFunc2(self: S) -> S
+}