From b548999b160d56554d7d524c6d733b629512bb33 Mon Sep 17 00:00:00 2001
From: Ewan Mellor <commits@ewanmellor.org>
Date: Thu, 9 Nov 2017 14:56:39 -0800
Subject: [PATCH] [Swift] Make DFA.precedenceDfa be a "let" rather than a
 "var".

Make DFA.precedenceDfa be a "let" rather than a "var", and remove
setPrecedenceDfa.  This field never varies after construction.  The
code in setPrecedenceDfa was carried over from the Java runtime, but
it only threw an exception, and was deprecated.  There's no need for
that in the Swift runtime.
---
 runtime/Swift/Sources/Antlr4/dfa/DFA.swift | 46 +++++++---------------
 1 file changed, 14 insertions(+), 32 deletions(-)

diff --git a/runtime/Swift/Sources/Antlr4/dfa/DFA.swift b/runtime/Swift/Sources/Antlr4/dfa/DFA.swift
index 3f8096ca1..ee0cab4b2 100644
--- a/runtime/Swift/Sources/Antlr4/dfa/DFA.swift
+++ b/runtime/Swift/Sources/Antlr4/dfa/DFA.swift
@@ -27,7 +27,7 @@ public class DFA: CustomStringConvertible {
     /// `true` if this DFA is for a precedence decision; otherwise,
     /// `false`. This is the backing field for _#isPrecedenceDfa_.
     /// 
-    private final var precedenceDfa: Bool
+    private let precedenceDfa: Bool
     
     /// 
     /// mutex for DFAState changes.
@@ -42,19 +42,19 @@ public class DFA: CustomStringConvertible {
         self.atnStartState = atnStartState
         self.decision = decision
 
-        var precedenceDfa: Bool = false
-        if atnStartState is StarLoopEntryState {
-            if (atnStartState as! StarLoopEntryState).precedenceRuleDecision {
-                precedenceDfa = true
-                let precedenceState: DFAState = DFAState(ATNConfigSet())
-                precedenceState.edges = [DFAState]() //new DFAState[0];
-                precedenceState.isAcceptState = false
-                precedenceState.requiresFullContext = false
-                self.s0 = precedenceState
-            }
-        }
+        if let starLoopState = atnStartState as? StarLoopEntryState, starLoopState.precedenceRuleDecision {
+            let precedenceState = DFAState(ATNConfigSet())
+            precedenceState.edges = [DFAState]()
+            precedenceState.isAcceptState = false
+            precedenceState.requiresFullContext = false
 
-        self.precedenceDfa = precedenceDfa
+            precedenceDfa = true
+            s0 = precedenceState
+        }
+        else {
+            precedenceDfa = false
+            s0 = nil
+        }
     }
 
     /// 
@@ -130,25 +130,7 @@ public class DFA: CustomStringConvertible {
         }
     }
 
-    /// 
-    /// Sets whether this is a precedence DFA.
-    /// 
-    /// - parameter precedenceDfa: `true` if this is a precedence DFA; otherwise,
-    /// `false`
-    /// 
-    /// - throws: ANTLRError.unsupportedOperation if `precedenceDfa` does not
-    /// match the value of _#isPrecedenceDfa_ for the current DFA.
-    /// 
-    /// - note: This method no longer performs any action.
-    /// 
-    public final func setPrecedenceDfa(_ precedenceDfa: Bool) throws {
-        if precedenceDfa != isPrecedenceDfa() {
-            throw ANTLRError.unsupportedOperation(msg: "The precedenceDfa field cannot change after a DFA is constructed.")
-
-        }
-    }
-
-    /// 
+    ///
     /// Return a list of all states in this DFA, ordered by state number.
     /// 
     public func getStates() -> Array<DFAState> {