Enable InlineArray type sugar

Promote it from an experimental feature.

rdar://155607927

Author: hamishknight

CodeGeneration/Sources/SyntaxSupport/ExperimentalFeatures.swift

@@ -21,7 +21,6 @@ public enum ExperimentalFeature: String, CaseIterable {
   case coroutineAccessors
   case keypathWithMethodMembers
   case oldOwnershipOperatorSpellings
-  case inlineArrayTypeSugar
   case defaultIsolationPerFile
 
   /// The name of the feature as it is written in the compiler's `Features.def` file.
@@ -43,8 +42,6 @@ public enum ExperimentalFeature: String, CaseIterable {
       return "KeypathWithMethodMembers"
     case .oldOwnershipOperatorSpellings:
       return "OldOwnershipOperatorSpellings"
-    case .inlineArrayTypeSugar:
-      return "InlineArrayTypeSugar"
     case .defaultIsolationPerFile:
       return "DefaultIsolationPerFile"
     }
@@ -69,8 +66,6 @@ public enum ExperimentalFeature: String, CaseIterable {
       return "keypaths with method members"
     case .oldOwnershipOperatorSpellings:
       return "`_move` and `_borrow` as ownership operators"
-    case .inlineArrayTypeSugar:
-      return "sugar type for InlineArray"
     case .defaultIsolationPerFile:
       return "set default actor isolation for a file"
     }

CodeGeneration/Sources/SyntaxSupport/TypeNodes.swift

@@ -302,7 +302,6 @@ public let TYPE_NODES: [Node] = [
   Node(
     kind: .inlineArrayType,
     base: .type,
-    experimentalFeature: .inlineArrayTypeSugar,
     nameForDiagnostics: "inline array type",
     documentation: "An inline array type `[3 of Int]`, sugar for `InlineArray<3, Int>`.",
     children: [

Sources/SwiftParser/Types.swift

@@ -646,8 +646,6 @@ extension Parser {
     unexpectedBeforeLSquare: RawUnexpectedNodesSyntax?,
     leftSquare: RawTokenSyntax
   ) -> RawTypeSyntax {
-    precondition(self.experimentalFeatures.contains(.inlineArrayTypeSugar))
-
     // We allow both values and types here and for the element type for
     // better recovery in cases where the user writes e.g '[Int of 3]'.
     let count = self.parseGenericArgumentType()
@@ -875,10 +873,6 @@ extension Parser.Lookahead {
   /// Checks whether we can parse the start of an InlineArray type. This does
   /// not include the element type.
   mutating func canParseStartOfInlineArrayTypeBody() -> Bool {
-    guard self.experimentalFeatures.contains(.inlineArrayTypeSugar) else {
-      return false
-    }
-
     // We must have at least '[<type-or-integer> of', which cannot be any other
     // kind of expression or type. We specifically look for both types and
     // integers for better recovery in e.g cases where the user writes e.g
@@ -907,7 +901,7 @@ extension Parser.Lookahead {
 
   mutating func canParseCollectionTypeBody() -> Bool {
     // Check to see if we have an InlineArray sugar type.
-    if self.experimentalFeatures.contains(.inlineArrayTypeSugar) {
+    do {
       var lookahead = self.lookahead()
       if lookahead.canParseInlineArrayTypeBody() {
         self = lookahead