YQ Connector:Use docker-compose in integrational tests

1 files changed, 911 insertions, 0 deletions

diff --git a/contrib/libs/antlr4_cpp_runtime/src/atn/ParserATNSimulator.h b/contrib/libs/antlr4_cpp_runtime/src/atn/ParserATNSimulator.h
new file mode 100644
index 0000000000..28fd059dd2
--- /dev/null
+++ b/contrib/libs/antlr4_cpp_runtime/src/atn/ParserATNSimulator.h
@@ -0,0 +1,911 @@
+/* Copyright (c) 2012-2017 The ANTLR Project. All rights reserved.
+ * Use of this file is governed by the BSD 3-clause license that
+ * can be found in the LICENSE.txt file in the project root.
+ */
+
+#pragma once
+
+#include "PredictionMode.h"
+#include "dfa/DFAState.h"
+#include "atn/ATNSimulator.h"
+#include "atn/PredictionContext.h"
+#include "atn/PredictionContextMergeCache.h"
+#include "atn/ParserATNSimulatorOptions.h"
+#include "SemanticContext.h"
+#include "atn/ATNConfig.h"
+
+namespace antlr4 {
+namespace atn {
+
+  /**
+   * The embodiment of the adaptive LL(*), ALL(*), parsing strategy.
+   *
+   * <p>
+   * The basic complexity of the adaptive strategy makes it harder to understand.
+   * We begin with ATN simulation to build paths in a DFA. Subsequent prediction
+   * requests go through the DFA first. If they reach a state without an edge for
+   * the current symbol, the algorithm fails over to the ATN simulation to
+   * complete the DFA path for the current input (until it finds a conflict state
+   * or uniquely predicting state).</p>
+   *
+   * <p>
+   * All of that is done without using the outer context because we want to create
+   * a DFA that is not dependent upon the rule invocation stack when we do a
+   * prediction. One DFA works in all contexts. We avoid using context not
+   * necessarily because it's slower, although it can be, but because of the DFA
+   * caching problem. The closure routine only considers the rule invocation stack
+   * created during prediction beginning in the decision rule. For example, if
+   * prediction occurs without invoking another rule's ATN, there are no context
+   * stacks in the configurations. When lack of context leads to a conflict, we
+   * don't know if it's an ambiguity or a weakness in the strong LL(*) parsing
+   * strategy (versus full LL(*)).</p>
+   *
+   * <p>
+   * When SLL yields a configuration set with conflict, we rewind the input and
+   * retry the ATN simulation, this time using full outer context without adding
+   * to the DFA. Configuration context stacks will be the full invocation stacks
+   * from the start rule. If we get a conflict using full context, then we can
+   * definitively say we have a true ambiguity for that input sequence. If we
+   * don't get a conflict, it implies that the decision is sensitive to the outer
+   * context. (It is not context-sensitive in the sense of context-sensitive
+   * grammars.)</p>
+   *
+   * <p>
+   * The next time we reach this DFA state with an SLL conflict, through DFA
+   * simulation, we will again retry the ATN simulation using full context mode.
+   * This is slow because we can't save the results and have to "interpret" the
+   * ATN each time we get that input.</p>
+   *
+   * <p>
+   * <strong>CACHING FULL CONTEXT PREDICTIONS</strong></p>
+   *
+   * <p>
+   * We could cache results from full context to predicted alternative easily and
+   * that saves a lot of time but doesn't work in presence of predicates. The set
+   * of visible predicates from the ATN start state changes depending on the
+   * context, because closure can fall off the end of a rule. I tried to cache
+   * tuples (stack context, semantic context, predicted alt) but it was slower
+   * than interpreting and much more complicated. Also required a huge amount of
+   * memory. The goal is not to create the world's fastest parser anyway. I'd like
+   * to keep this algorithm simple. By launching multiple threads, we can improve
+   * the speed of parsing across a large number of files.</p>
+   *
+   * <p>
+   * There is no strict ordering between the amount of input used by SLL vs LL,
+   * which makes it really hard to build a cache for full context. Let's say that
+   * we have input A B C that leads to an SLL conflict with full context X. That
+   * implies that using X we might only use A B but we could also use A B C D to
+   * resolve conflict. Input A B C D could predict alternative 1 in one position
+   * in the input and A B C E could predict alternative 2 in another position in
+   * input. The conflicting SLL configurations could still be non-unique in the
+   * full context prediction, which would lead us to requiring more input than the
+   * original A B C.	To make a	prediction cache work, we have to track	the exact
+   * input	used during the previous prediction. That amounts to a cache that maps
+   * X to a specific DFA for that context.</p>
+   *
+   * <p>
+   * Something should be done for left-recursive expression predictions. They are
+   * likely LL(1) + pred eval. Easier to do the whole SLL unless error and retry
+   * with full LL thing Sam does.</p>
+   *
+   * <p>
+   * <strong>AVOIDING FULL CONTEXT PREDICTION</strong></p>
+   *
+   * <p>
+   * We avoid doing full context retry when the outer context is empty, we did not
+   * dip into the outer context by falling off the end of the decision state rule,
+   * or when we force SLL mode.</p>
+   *
+   * <p>
+   * As an example of the not dip into outer context case, consider as super
+   * constructor calls versus function calls. One grammar might look like
+   * this:</p>
+   *
+   * <pre>
+   * ctorBody
+   *   : '{' superCall? stat* '}'
+   *   ;
+   * </pre>
+   *
+   * <p>
+   * Or, you might see something like</p>
+   *
+   * <pre>
+   * stat
+   *   : superCall ';'
+   *   | expression ';'
+   *   | ...
+   *   ;
+   * </pre>
+   *
+   * <p>
+   * In both cases I believe that no closure operations will dip into the outer
+   * context. In the first case ctorBody in the worst case will stop at the '}'.
+   * In the 2nd case it should stop at the ';'. Both cases should stay within the
+   * entry rule and not dip into the outer context.</p>
+   *
+   * <p>
+   * <strong>PREDICATES</strong></p>
+   *
+   * <p>
+   * Predicates are always evaluated if present in either SLL or LL both. SLL and
+   * LL simulation deals with predicates differently. SLL collects predicates as
+   * it performs closure operations like ANTLR v3 did. It delays predicate
+   * evaluation until it reaches and accept state. This allows us to cache the SLL
+   * ATN simulation whereas, if we had evaluated predicates on-the-fly during
+   * closure, the DFA state configuration sets would be different and we couldn't
+   * build up a suitable DFA.</p>
+   *
+   * <p>
+   * When building a DFA accept state during ATN simulation, we evaluate any
+   * predicates and return the sole semantically valid alternative. If there is
+   * more than 1 alternative, we report an ambiguity. If there are 0 alternatives,
+   * we throw an exception. Alternatives without predicates act like they have
+   * true predicates. The simple way to think about it is to strip away all
+   * alternatives with false predicates and choose the minimum alternative that
+   * remains.</p>
+   *
+   * <p>
+   * When we start in the DFA and reach an accept state that's predicated, we test
+   * those and return the minimum semantically viable alternative. If no
+   * alternatives are viable, we throw an exception.</p>
+   *
+   * <p>
+   * During full LL ATN simulation, closure always evaluates predicates and
+   * on-the-fly. This is crucial to reducing the configuration set size during
+   * closure. It hits a landmine when parsing with the Java grammar, for example,
+   * without this on-the-fly evaluation.</p>
+   *
+   * <p>
+   * <strong>SHARING DFA</strong></p>
+   *
+   * <p>
+   * All instances of the same parser share the same decision DFAs through a
+   * static field. Each instance gets its own ATN simulator but they share the
+   * same {@link #decisionToDFA} field. They also share a
+   * {@link PredictionContextCache} object that makes sure that all
+   * {@link PredictionContext} objects are shared among the DFA states. This makes
+   * a big size difference.</p>
+   *
+   * <p>
+   * <strong>THREAD SAFETY</strong></p>
+   *
+   * <p>
+   * The {@link ParserATNSimulator} locks on the {@link #decisionToDFA} field when
+   * it adds a new DFA object to that array. {@link #addDFAEdge}
+   * locks on the DFA for the current decision when setting the
+   * {@link DFAState#edges} field. {@link #addDFAState} locks on
+   * the DFA for the current decision when looking up a DFA state to see if it
+   * already exists. We must make sure that all requests to add DFA states that
+   * are equivalent result in the same shared DFA object. This is because lots of
+   * threads will be trying to update the DFA at once. The
+   * {@link #addDFAState} method also locks inside the DFA lock
+   * but this time on the shared context cache when it rebuilds the
+   * configurations' {@link PredictionContext} objects using cached
+   * subgraphs/nodes. No other locking occurs, even during DFA simulation. This is
+   * safe as long as we can guarantee that all threads referencing
+   * {@code s.edge[t]} get the same physical target {@link DFAState}, or
+   * {@code null}. Once into the DFA, the DFA simulation does not reference the
+   * {@link DFA#states} map. It follows the {@link DFAState#edges} field to new
+   * targets. The DFA simulator will either find {@link DFAState#edges} to be
+   * {@code null}, to be non-{@code null} and {@code dfa.edges[t]} null, or
+   * {@code dfa.edges[t]} to be non-null. The
+   * {@link #addDFAEdge} method could be racing to set the field
+   * but in either case the DFA simulator works; if {@code null}, and requests ATN
+   * simulation. It could also race trying to get {@code dfa.edges[t]}, but either
+   * way it will work because it's not doing a test and set operation.</p>
+   *
+   * <p>
+   * <strong>Starting with SLL then failing to combined SLL/LL (Two-Stage
+   * Parsing)</strong></p>
+   *
+   * <p>
+   * Sam pointed out that if SLL does not give a syntax error, then there is no
+   * point in doing full LL, which is slower. We only have to try LL if we get a
+   * syntax error. For maximum speed, Sam starts the parser set to pure SLL
+   * mode with the {@link BailErrorStrategy}:</p>
+   *
+   * <pre>
+   * parser.{@link Parser#getInterpreter() getInterpreter()}.{@link #setPredictionMode setPredictionMode}{@code (}{@link PredictionMode#SLL}{@code )};
+   * parser.{@link Parser#setErrorHandler setErrorHandler}(new {@link BailErrorStrategy}());
+   * </pre>
+   *
+   * <p>
+   * If it does not get a syntax error, then we're done. If it does get a syntax
+   * error, we need to retry with the combined SLL/LL strategy.</p>
+   *
+   * <p>
+   * The reason this works is as follows. If there are no SLL conflicts, then the
+   * grammar is SLL (at least for that input set). If there is an SLL conflict,
+   * the full LL analysis must yield a set of viable alternatives which is a
+   * subset of the alternatives reported by SLL. If the LL set is a singleton,
+   * then the grammar is LL but not SLL. If the LL set is the same size as the SLL
+   * set, the decision is SLL. If the LL set has size &gt; 1, then that decision
+   * is truly ambiguous on the current input. If the LL set is smaller, then the
+   * SLL conflict resolution might choose an alternative that the full LL would
+   * rule out as a possibility based upon better context information. If that's
+   * the case, then the SLL parse will definitely get an error because the full LL
+   * analysis says it's not viable. If SLL conflict resolution chooses an
+   * alternative within the LL set, them both SLL and LL would choose the same
+   * alternative because they both choose the minimum of multiple conflicting
+   * alternatives.</p>
+   *
+   * <p>
+   * Let's say we have a set of SLL conflicting alternatives {@code {1, 2, 3}} and
+   * a smaller LL set called <em>s</em>. If <em>s</em> is {@code {2, 3}}, then SLL
+   * parsing will get an error because SLL will pursue alternative 1. If
+   * <em>s</em> is {@code {1, 2}} or {@code {1, 3}} then both SLL and LL will
+   * choose the same alternative because alternative one is the minimum of either
+   * set. If <em>s</em> is {@code {2}} or {@code {3}} then SLL will get a syntax
+   * error. If <em>s</em> is {@code {1}} then SLL will succeed.</p>
+   *
+   * <p>
+   * Of course, if the input is invalid, then we will get an error for sure in
+   * both SLL and LL parsing. Erroneous input will therefore require 2 passes over
+   * the input.</p>
+   */
+  class ANTLR4CPP_PUBLIC ParserATNSimulator : public ATNSimulator {
+  public:
+    /// Testing only!
+    ParserATNSimulator(const ATN &atn, std::vector<dfa::DFA> &decisionToDFA,
+                       PredictionContextCache &sharedContextCache);
+
+    ParserATNSimulator(Parser *parser, const ATN &atn, std::vector<dfa::DFA> &decisionToDFA,
+                       PredictionContextCache &sharedContextCache);
+
+    ParserATNSimulator(Parser *parser, const ATN &atn, std::vector<dfa::DFA> &decisionToDFA,
+                       PredictionContextCache &sharedContextCache,
+                       const ParserATNSimulatorOptions &options);
+
+    virtual void reset() override;
+    virtual void clearDFA() override;
+    virtual size_t adaptivePredict(TokenStream *input, size_t decision, ParserRuleContext *outerContext);
+
+    static const bool TURN_OFF_LR_LOOP_ENTRY_BRANCH_OPT;
+
+    std::vector<dfa::DFA> &decisionToDFA;
+
+    /** Implements first-edge (loop entry) elimination as an optimization
+     *  during closure operations.  See antlr/antlr4#1398.
+     *
+     * The optimization is to avoid adding the loop entry config when
+     * the exit path can only lead back to the same
+     * StarLoopEntryState after popping context at the rule end state
+     * (traversing only epsilon edges, so we're still in closure, in
+     * this same rule).
+     *
+     * We need to detect any state that can reach loop entry on
+     * epsilon w/o exiting rule. We don't have to look at FOLLOW
+     * links, just ensure that all stack tops for config refer to key
+     * states in LR rule.
+     *
+     * To verify we are in the right situation we must first check
+     * closure is at a StarLoopEntryState generated during LR removal.
+     * Then we check that each stack top of context is a return state
+     * from one of these cases:
+     *
+     *   1. 'not' expr, '(' type ')' expr. The return state points at loop entry state
+     *   2. expr op expr. The return state is the block end of internal block of (...)*
+     *   3. 'between' expr 'and' expr. The return state of 2nd expr reference.
+     *      That state points at block end of internal block of (...)*.
+     *   4. expr '?' expr ':' expr. The return state points at block end,
+     *      which points at loop entry state.
+     *
+     * If any is true for each stack top, then closure does not add a
+     * config to the current config set for edge[0], the loop entry branch.
+     *
+     *  Conditions fail if any context for the current config is:
+     *
+     *   a. empty (we'd fall out of expr to do a global FOLLOW which could
+     *      even be to some weird spot in expr) or,
+     *   b. lies outside of expr or,
+     *   c. lies within expr but at a state not the BlockEndState
+     *   generated during LR removal
+     *
+     * Do we need to evaluate predicates ever in closure for this case?
+     *
+     * No. Predicates, including precedence predicates, are only
+     * evaluated when computing a DFA start state. I.e., only before
+     * the lookahead (but not parser) consumes a token.
+     *
+     * There are no epsilon edges allowed in LR rule alt blocks or in
+     * the "primary" part (ID here). If closure is in
+     * StarLoopEntryState any lookahead operation will have consumed a
+     * token as there are no epsilon-paths that lead to
+     * StarLoopEntryState. We do not have to evaluate predicates
+     * therefore if we are in the generated StarLoopEntryState of a LR
+     * rule. Note that when making a prediction starting at that
+     * decision point, decision d=2, compute-start-state performs
+     * closure starting at edges[0], edges[1] emanating from
+     * StarLoopEntryState. That means it is not performing closure on
+     * StarLoopEntryState during compute-start-state.
+     *
+     * How do we know this always gives same prediction answer?
+     *
+     * Without predicates, loop entry and exit paths are ambiguous
+     * upon remaining input +b (in, say, a+b). Either paths lead to
+     * valid parses. Closure can lead to consuming + immediately or by
+     * falling out of this call to expr back into expr and loop back
+     * again to StarLoopEntryState to match +b. In this special case,
+     * we choose the more efficient path, which is to take the bypass
+     * path.
+     *
+     * The lookahead language has not changed because closure chooses
+     * one path over the other. Both paths lead to consuming the same
+     * remaining input during a lookahead operation. If the next token
+     * is an operator, lookahead will enter the choice block with
+     * operators. If it is not, lookahead will exit expr. Same as if
+     * closure had chosen to enter the choice block immediately.
+     *
+     * Closure is examining one config (some loopentrystate, some alt,
+     * context) which means it is considering exactly one alt. Closure
+     * always copies the same alt to any derived configs.
+     *
+     * How do we know this optimization doesn't mess up precedence in
+     * our parse trees?
+     *
+     * Looking through expr from left edge of stat only has to confirm
+     * that an input, say, a+b+c; begins with any valid interpretation
+     * of an expression. The precedence actually doesn't matter when
+     * making a decision in stat seeing through expr. It is only when
+     * parsing rule expr that we must use the precedence to get the
+     * right interpretation and, hence, parse tree.
+     */
+    bool canDropLoopEntryEdgeInLeftRecursiveRule(ATNConfig *config) const;
+    virtual std::string getRuleName(size_t index);
+
+    virtual Ref<ATNConfig> precedenceTransition(Ref<ATNConfig> const& config, const PrecedencePredicateTransition *pt,
+                                                bool collectPredicates, bool inContext, bool fullCtx);
+
+    void setPredictionMode(PredictionMode newMode);
+    PredictionMode getPredictionMode();
+
+    Parser* getParser();
+
+    virtual std::string getTokenName(size_t t);
+
+    virtual std::string getLookaheadName(TokenStream *input);
+
+    /// <summary>
+    /// Used for debugging in adaptivePredict around execATN but I cut
+    ///  it out for clarity now that alg. works well. We can leave this
+    ///  "dead" code for a bit.
+    /// </summary>
+    virtual void dumpDeadEndConfigs(NoViableAltException &nvae);
+
+  protected:
+    Parser *const parser;
+
+    /// <summary>
+    /// Each prediction operation uses a cache for merge of prediction contexts.
+    /// Don't keep around as it wastes huge amounts of memory. The merge cache
+    /// isn't synchronized but we're ok since two threads shouldn't reuse same
+    /// parser/atnsim object because it can only handle one input at a time.
+    /// This maps graphs a and b to merged result c. (a,b)->c. We can avoid
+    /// the merge if we ever see a and b again.  Note that (b,a)->c should
+    /// also be examined during cache lookup.
+    /// </summary>
+    PredictionContextMergeCache mergeCache;
+    size_t _mergeCacheCounter = 0;
+
+    // LAME globals to avoid parameters!!!!! I need these down deep in predTransition
+    TokenStream *_input;
+    size_t _startIndex;
+    ParserRuleContext *_outerContext;
+    dfa::DFA *_dfa; // Reference into the decisionToDFA vector.
+
+    /// <summary>
+    /// Performs ATN simulation to compute a predicted alternative based
+    ///  upon the remaining input, but also updates the DFA cache to avoid
+    ///  having to traverse the ATN again for the same input sequence.
+    ///
+    /// There are some key conditions we're looking for after computing a new
+    /// set of ATN configs (proposed DFA state):
+    /// if the set is empty, there is no viable alternative for current symbol
+    /// does the state uniquely predict an alternative?
+    /// does the state have a conflict that would prevent us from
+    ///         putting it on the work list?
+    ///
+    /// We also have some key operations to do:
+    /// add an edge from previous DFA state to potentially new DFA state, D,
+    ///         upon current symbol but only if adding to work list, which means in all
+    ///         cases except no viable alternative (and possibly non-greedy decisions?)
+    /// collecting predicates and adding semantic context to DFA accept states
+    /// adding rule context to context-sensitive DFA accept states
+    /// consuming an input symbol
+    /// reporting a conflict
+    /// reporting an ambiguity
+    /// reporting a context sensitivity
+    /// reporting insufficient predicates
+    ///
+    /// cover these cases:
+    ///    dead end
+    ///    single alt
+    ///    single alt + preds
+    ///    conflict
+    ///    conflict + preds
+    /// </summary>
+    virtual size_t execATN(dfa::DFA &dfa, dfa::DFAState *s0, TokenStream *input, size_t startIndex,
+                           ParserRuleContext *outerContext);
+
+    /// <summary>
+    /// Get an existing target state for an edge in the DFA. If the target state
+    /// for the edge has not yet been computed or is otherwise not available,
+    /// this method returns {@code null}.
+    /// </summary>
+    /// <param name="previousD"> The current DFA state </param>
+    /// <param name="t"> The next input symbol </param>
+    /// <returns> The existing target DFA state for the given input symbol
+    /// {@code t}, or {@code null} if the target state for this edge is not
+    /// already cached </returns>
+    virtual dfa::DFAState* getExistingTargetState(dfa::DFAState *previousD, size_t t);
+
+    /// <summary>
+    /// Compute a target state for an edge in the DFA, and attempt to add the
+    /// computed state and corresponding edge to the DFA.
+    /// </summary>
+    /// <param name="dfa"> The DFA </param>
+    /// <param name="previousD"> The current DFA state </param>
+    /// <param name="t"> The next input symbol
+    /// </param>
+    /// <returns> The computed target DFA state for the given input symbol
+    /// {@code t}. If {@code t} does not lead to a valid DFA state, this method
+    /// returns <seealso cref="#ERROR"/>. </returns>
+    virtual dfa::DFAState *computeTargetState(dfa::DFA &dfa, dfa::DFAState *previousD, size_t t);
+
+    virtual void predicateDFAState(dfa::DFAState *dfaState, DecisionState *decisionState);
+
+    // comes back with reach.uniqueAlt set to a valid alt
+    virtual size_t execATNWithFullContext(dfa::DFA &dfa, dfa::DFAState *D, ATNConfigSet *s0,
+                                          TokenStream *input, size_t startIndex, ParserRuleContext *outerContext); // how far we got before failing over
+
+    virtual std::unique_ptr<ATNConfigSet> computeReachSet(ATNConfigSet *closure, size_t t, bool fullCtx);
+
+    /// <summary>
+    /// Return a configuration set containing only the configurations from
+    /// {@code configs} which are in a <seealso cref="RuleStopState"/>. If all
+    /// configurations in {@code configs} are already in a rule stop state, this
+    /// method simply returns {@code configs}.
+    /// <p/>
+    /// When {@code lookToEndOfRule} is true, this method uses
+    /// <seealso cref="ATN#nextTokens"/> for each configuration in {@code configs} which is
+    /// not already in a rule stop state to see if a rule stop state is reachable
+    /// from the configuration via epsilon-only transitions.
+    /// </summary>
+    /// <param name="configs"> the configuration set to update </param>
+    /// <param name="lookToEndOfRule"> when true, this method checks for rule stop states
+    /// reachable by epsilon-only transitions from each configuration in
+    /// {@code configs}.
+    /// </param>
+    /// <returns> {@code configs} if all configurations in {@code configs} are in a
+    /// rule stop state, otherwise return a new configuration set containing only
+    /// the configurations from {@code configs} which are in a rule stop state </returns>
+    virtual ATNConfigSet* removeAllConfigsNotInRuleStopState(ATNConfigSet *configs, bool lookToEndOfRule);
+
+    virtual std::unique_ptr<ATNConfigSet> computeStartState(ATNState *p, RuleContext *ctx, bool fullCtx);
+
+    /* parrt internal source braindump that doesn't mess up
+     * external API spec.
+
+     applyPrecedenceFilter is an optimization to avoid highly
+     nonlinear prediction of expressions and other left recursive
+     rules. The precedence predicates such as {3>=prec}? Are highly
+     context-sensitive in that they can only be properly evaluated
+     in the context of the proper prec argument. Without pruning,
+     these predicates are normal predicates evaluated when we reach
+     conflict state (or unique prediction). As we cannot evaluate
+     these predicates out of context, the resulting conflict leads
+     to full LL evaluation and nonlinear prediction which shows up
+     very clearly with fairly large expressions.
+
+     Example grammar:
+
+     e : e '*' e
+     | e '+' e
+     | INT
+     ;
+
+     We convert that to the following:
+
+     e[int prec]
+     :   INT
+     ( {3>=prec}? '*' e[4]
+     | {2>=prec}? '+' e[3]
+     )*
+     ;
+
+     The (..)* loop has a decision for the inner block as well as
+     an enter or exit decision, which is what concerns us here. At
+     the 1st + of input 1+2+3, the loop entry sees both predicates
+     and the loop exit also sees both predicates by falling off the
+     edge of e.  This is because we have no stack information with
+     SLL and find the follow of e, which will hit the return states
+     inside the loop after e[4] and e[3], which brings it back to
+     the enter or exit decision. In this case, we know that we
+     cannot evaluate those predicates because we have fallen off
+     the edge of the stack and will in general not know which prec
+     parameter is the right one to use in the predicate.
+
+     Because we have special information, that these are precedence
+     predicates, we can resolve them without failing over to full
+     LL despite their context sensitive nature. We make an
+     assumption that prec[-1] <= prec[0], meaning that the current
+     precedence level is greater than or equal to the precedence
+     level of recursive invocations above us in the stack. For
+     example, if predicate {3>=prec}? is true of the current prec,
+     then one option is to enter the loop to match it now. The
+     other option is to exit the loop and the left recursive rule
+     to match the current operator in rule invocation further up
+     the stack. But, we know that all of those prec are lower or
+     the same value and so we can decide to enter the loop instead
+     of matching it later. That means we can strip out the other
+     configuration for the exit branch.
+
+     So imagine we have (14,1,$,{2>=prec}?) and then
+     (14,2,$-dipsIntoOuterContext,{2>=prec}?). The optimization
+     allows us to collapse these two configurations. We know that
+     if {2>=prec}? is true for the current prec parameter, it will
+     also be true for any prec from an invoking e call, indicated
+     by dipsIntoOuterContext. As the predicates are both true, we
+     have the option to evaluate them early in the decision start
+     state. We do this by stripping both predicates and choosing to
+     enter the loop as it is consistent with the notion of operator
+     precedence. It's also how the full LL conflict resolution
+     would work.
+
+     The solution requires a different DFA start state for each
+     precedence level.
+
+     The basic filter mechanism is to remove configurations of the
+     form (p, 2, pi) if (p, 1, pi) exists for the same p and pi. In
+     other words, for the same ATN state and predicate context,
+     remove any configuration associated with an exit branch if
+     there is a configuration associated with the enter branch.
+
+     It's also the case that the filter evaluates precedence
+     predicates and resolves conflicts according to precedence
+     levels. For example, for input 1+2+3 at the first +, we see
+     prediction filtering
+
+     [(11,1,[$],{3>=prec}?), (14,1,[$],{2>=prec}?), (5,2,[$],up=1),
+     (11,2,[$],up=1), (14,2,[$],up=1)],hasSemanticContext=true,dipsIntoOuterContext
+
+     to
+
+     [(11,1,[$]), (14,1,[$]), (5,2,[$],up=1)],dipsIntoOuterContext
+
+     This filters because {3>=prec}? evals to true and collapses
+     (11,1,[$],{3>=prec}?) and (11,2,[$],up=1) since early conflict
+     resolution based upon rules of operator precedence fits with
+     our usual match first alt upon conflict.
+
+     We noticed a problem where a recursive call resets precedence
+     to 0. Sam's fix: each config has flag indicating if it has
+     returned from an expr[0] call. then just don't filter any
+     config with that flag set. flag is carried along in
+     closure(). so to avoid adding field, set bit just under sign
+     bit of dipsIntoOuterContext (SUPPRESS_PRECEDENCE_FILTER).
+     With the change you filter "unless (p, 2, pi) was reached
+     after leaving the rule stop state of the LR rule containing
+     state p, corresponding to a rule invocation with precedence
+     level 0"
+     */
+
+    /**
+     * This method transforms the start state computed by
+     * {@link #computeStartState} to the special start state used by a
+     * precedence DFA for a particular precedence value. The transformation
+     * process applies the following changes to the start state's configuration
+     * set.
+     *
+     * <ol>
+     * <li>Evaluate the precedence predicates for each configuration using
+     * {@link SemanticContext#evalPrecedence}.</li>
+     * <li>When {@link ATNConfig#isPrecedenceFilterSuppressed} is {@code false},
+     * remove all configurations which predict an alternative greater than 1,
+     * for which another configuration that predicts alternative 1 is in the
+     * same ATN state with the same prediction context. This transformation is
+     * valid for the following reasons:
+     * <ul>
+     * <li>The closure block cannot contain any epsilon transitions which bypass
+     * the body of the closure, so all states reachable via alternative 1 are
+     * part of the precedence alternatives of the transformed left-recursive
+     * rule.</li>
+     * <li>The "primary" portion of a left recursive rule cannot contain an
+     * epsilon transition, so the only way an alternative other than 1 can exist
+     * in a state that is also reachable via alternative 1 is by nesting calls
+     * to the left-recursive rule, with the outer calls not being at the
+     * preferred precedence level. The
+     * {@link ATNConfig#isPrecedenceFilterSuppressed} property marks ATN
+     * configurations which do not meet this condition, and therefore are not
+     * eligible for elimination during the filtering process.</li>
+     * </ul>
+     * </li>
+     * </ol>
+     *
+     * <p>
+     * The prediction context must be considered by this filter to address
+     * situations like the following.
+     * </p>
+     * <code>
+     * <pre>
+     * grammar TA;
+     * prog: statement* EOF;
+     * statement: letterA | statement letterA 'b' ;
+     * letterA: 'a';
+     * </pre>
+     * </code>
+     * <p>
+     * If the above grammar, the ATN state immediately before the token
+     * reference {@code 'a'} in {@code letterA} is reachable from the left edge
+     * of both the primary and closure blocks of the left-recursive rule
+     * {@code statement}. The prediction context associated with each of these
+     * configurations distinguishes between them, and prevents the alternative
+     * which stepped out to {@code prog} (and then back in to {@code statement}
+     * from being eliminated by the filter.
+     * </p>
+     *
+     * @param configs The configuration set computed by
+     * {@link #computeStartState} as the start state for the DFA.
+     * @return The transformed configuration set representing the start state
+     * for a precedence DFA at a particular precedence level (determined by
+     * calling {@link Parser#getPrecedence}).
+     */
+    std::unique_ptr<ATNConfigSet> applyPrecedenceFilter(ATNConfigSet *configs);
+
+    virtual ATNState *getReachableTarget(const Transition *trans, size_t ttype);
+
+    virtual std::vector<Ref<const SemanticContext>> getPredsForAmbigAlts(const antlrcpp::BitSet &ambigAlts,
+                                                                   ATNConfigSet *configs, size_t nalts);
+
+    std::vector<dfa::DFAState::PredPrediction> getPredicatePredictions(const antlrcpp::BitSet &ambigAlts,
+                                                                       const std::vector<Ref<const SemanticContext>> &altToPred);
+
+    /**
+     * This method is used to improve the localization of error messages by
+     * choosing an alternative rather than throwing a
+     * {@link NoViableAltException} in particular prediction scenarios where the
+     * {@link #ERROR} state was reached during ATN simulation.
+     *
+     * <p>
+     * The default implementation of this method uses the following
+     * algorithm to identify an ATN configuration which successfully parsed the
+     * decision entry rule. Choosing such an alternative ensures that the
+     * {@link ParserRuleContext} returned by the calling rule will be complete
+     * and valid, and the syntax error will be reported later at a more
+     * localized location.</p>
+     *
+     * <ul>
+     * <li>If a syntactically valid path or paths reach the end of the decision rule and
+     * they are semantically valid if predicated, return the min associated alt.</li>
+     * <li>Else, if a semantically invalid but syntactically valid path exist
+     * or paths exist, return the minimum associated alt.
+     * </li>
+     * <li>Otherwise, return {@link ATN#INVALID_ALT_NUMBER}.</li>
+     * </ul>
+     *
+     * <p>
+     * In some scenarios, the algorithm described above could predict an
+     * alternative which will result in a {@link FailedPredicateException} in
+     * the parser. Specifically, this could occur if the <em>only</em> configuration
+     * capable of successfully parsing to the end of the decision rule is
+     * blocked by a semantic predicate. By choosing this alternative within
+     * {@link #adaptivePredict} instead of throwing a
+     * {@link NoViableAltException}, the resulting
+     * {@link FailedPredicateException} in the parser will identify the specific
+     * predicate which is preventing the parser from successfully parsing the
+     * decision rule, which helps developers identify and correct logic errors
+     * in semantic predicates.
+     * </p>
+     *
+     * @param configs The ATN configurations which were valid immediately before
+     * the {@link #ERROR} state was reached
+     * @param outerContext The is the \gamma_0 initial parser context from the paper
+     * or the parser stack at the instant before prediction commences.
+     *
+     * @return The value to return from {@link #adaptivePredict}, or
+     * {@link ATN#INVALID_ALT_NUMBER} if a suitable alternative was not
+     * identified and {@link #adaptivePredict} should report an error instead.
+     */
+    size_t getSynValidOrSemInvalidAltThatFinishedDecisionEntryRule(ATNConfigSet *configs,
+                                                                   ParserRuleContext *outerContext);
+
+    virtual size_t getAltThatFinishedDecisionEntryRule(ATNConfigSet *configs);
+
+    /** Walk the list of configurations and split them according to
+     *  those that have preds evaluating to true/false.  If no pred, assume
+     *  true pred and include in succeeded set.  Returns Pair of sets.
+     *
+     *  Create a new set so as not to alter the incoming parameter.
+     *
+     *  Assumption: the input stream has been restored to the starting point
+     *  prediction, which is where predicates need to evaluate.
+     */
+    std::pair<ATNConfigSet *, ATNConfigSet *> splitAccordingToSemanticValidity(ATNConfigSet *configs,
+                                                                               ParserRuleContext *outerContext);
+
+    /// <summary>
+    /// Look through a list of predicate/alt pairs, returning alts for the
+    ///  pairs that win. A {@code NONE} predicate indicates an alt containing an
+    ///  unpredicated config which behaves as "always true." If !complete
+    ///  then we stop at the first predicate that evaluates to true. This
+    ///  includes pairs with null predicates.
+    /// </summary>
+    antlrcpp::BitSet evalSemanticContext(const std::vector<dfa::DFAState::PredPrediction> &predPredictions,
+                                         ParserRuleContext *outerContext, bool complete);
+
+    /**
+     * Evaluate a semantic context within a specific parser context.
+     *
+     * <p>
+     * This method might not be called for every semantic context evaluated
+     * during the prediction process. In particular, we currently do not
+     * evaluate the following but it may change in the future:</p>
+     *
+     * <ul>
+     * <li>Precedence predicates (represented by
+     * {@link SemanticContext.PrecedencePredicate}) are not currently evaluated
+     * through this method.</li>
+     * <li>Operator predicates (represented by {@link SemanticContext.AND} and
+     * {@link SemanticContext.OR}) are evaluated as a single semantic
+     * context, rather than evaluating the operands individually.
+     * Implementations which require evaluation results from individual
+     * predicates should override this method to explicitly handle evaluation of
+     * the operands within operator predicates.</li>
+     * </ul>
+     *
+     * @param pred The semantic context to evaluate
+     * @param parserCallStack The parser context in which to evaluate the
+     * semantic context
+     * @param alt The alternative which is guarded by {@code pred}
+     * @param fullCtx {@code true} if the evaluation is occurring during LL
+     * prediction; otherwise, {@code false} if the evaluation is occurring
+     * during SLL prediction
+     *
+     * @since 4.3
+     */
+    virtual bool evalSemanticContext(Ref<const SemanticContext> const& pred, ParserRuleContext *parserCallStack,
+                                     size_t alt, bool fullCtx);
+
+    /* TODO: If we are doing predicates, there is no point in pursuing
+     closure operations if we reach a DFA state that uniquely predicts
+     alternative. We will not be caching that DFA state and it is a
+     waste to pursue the closure. Might have to advance when we do
+     ambig detection thought :(
+     */
+    virtual void closure(Ref<ATNConfig> const& config, ATNConfigSet *configs, ATNConfig::Set &closureBusy,
+                         bool collectPredicates, bool fullCtx, bool treatEofAsEpsilon);
+
+    virtual void closureCheckingStopState(Ref<ATNConfig> const& config, ATNConfigSet *configs, ATNConfig::Set &closureBusy,
+                                          bool collectPredicates, bool fullCtx, int depth, bool treatEofAsEpsilon);
+
+    /// Do the actual work of walking epsilon edges.
+    virtual void closure_(Ref<ATNConfig> const& config, ATNConfigSet *configs, ATNConfig::Set &closureBusy,
+                          bool collectPredicates, bool fullCtx, int depth, bool treatEofAsEpsilon);
+
+    virtual Ref<ATNConfig> getEpsilonTarget(Ref<ATNConfig> const& config, const Transition *t, bool collectPredicates,
+                                            bool inContext, bool fullCtx, bool treatEofAsEpsilon);
+    virtual Ref<ATNConfig> actionTransition(Ref<ATNConfig> const& config, const ActionTransition *t);
+
+    virtual Ref<ATNConfig> predTransition(Ref<ATNConfig> const& config, const PredicateTransition *pt, bool collectPredicates,
+                                          bool inContext, bool fullCtx);
+
+    virtual Ref<ATNConfig> ruleTransition(Ref<ATNConfig> const& config, const RuleTransition *t);
+
+    /**
+     * Gets a {@link BitSet} containing the alternatives in {@code configs}
+     * which are part of one or more conflicting alternative subsets.
+     *
+     * @param configs The {@link ATNConfigSet} to analyze.
+     * @return The alternatives in {@code configs} which are part of one or more
+     * conflicting alternative subsets. If {@code configs} does not contain any
+     * conflicting subsets, this method returns an empty {@link BitSet}.
+     */
+    virtual antlrcpp::BitSet getConflictingAlts(ATNConfigSet *configs);
+
+    /// <summary>
+    /// Sam pointed out a problem with the previous definition, v3, of
+    /// ambiguous states. If we have another state associated with conflicting
+    /// alternatives, we should keep going. For example, the following grammar
+    ///
+    /// s : (ID | ID ID?) ';' ;
+    ///
+    /// When the ATN simulation reaches the state before ';', it has a DFA
+    /// state that looks like: [12|1|[], 6|2|[], 12|2|[]]. Naturally
+    /// 12|1|[] and 12|2|[] conflict, but we cannot stop processing this node
+    /// because alternative to has another way to continue, via [6|2|[]].
+    /// The key is that we have a single state that has config's only associated
+    /// with a single alternative, 2, and crucially the state transitions
+    /// among the configurations are all non-epsilon transitions. That means
+    /// we don't consider any conflicts that include alternative 2. So, we
+    /// ignore the conflict between alts 1 and 2. We ignore a set of
+    /// conflicting alts when there is an intersection with an alternative
+    /// associated with a single alt state in the state->config-list map.
+    ///
+    /// It's also the case that we might have two conflicting configurations but
+    /// also a 3rd nonconflicting configuration for a different alternative:
+    /// [1|1|[], 1|2|[], 8|3|[]]. This can come about from grammar:
+    ///
+    /// a : A | A | A B ;
+    ///
+    /// After matching input A, we reach the stop state for rule A, state 1.
+    /// State 8 is the state right before B. Clearly alternatives 1 and 2
+    /// conflict and no amount of further lookahead will separate the two.
+    /// However, alternative 3 will be able to continue and so we do not
+    /// stop working on this state. In the previous example, we're concerned
+    /// with states associated with the conflicting alternatives. Here alt
+    /// 3 is not associated with the conflicting configs, but since we can continue
+    /// looking for input reasonably, I don't declare the state done. We
+    /// ignore a set of conflicting alts when we have an alternative
+    /// that we still need to pursue.
+    /// </summary>
+
+    virtual antlrcpp::BitSet getConflictingAltsOrUniqueAlt(ATNConfigSet *configs);
+
+    virtual NoViableAltException noViableAlt(TokenStream *input, ParserRuleContext *outerContext,
+                                              ATNConfigSet *configs, size_t startIndex, bool deleteConfigs);
+
+    static size_t getUniqueAlt(ATNConfigSet *configs);
+
+    /// <summary>
+    /// Add an edge to the DFA, if possible. This method calls
+    /// <seealso cref="#addDFAState"/> to ensure the {@code to} state is present in the
+    /// DFA. If {@code from} is {@code null}, or if {@code t} is outside the
+    /// range of edges that can be represented in the DFA tables, this method
+    /// returns without adding the edge to the DFA.
+    /// <p/>
+    /// If {@code to} is {@code null}, this method returns {@code null}.
+    /// Otherwise, this method returns the <seealso cref="DFAState"/> returned by calling
+    /// <seealso cref="#addDFAState"/> for the {@code to} state.
+    /// </summary>
+    /// <param name="dfa"> The DFA </param>
+    /// <param name="from"> The source state for the edge </param>
+    /// <param name="t"> The input symbol </param>
+    /// <param name="to"> The target state for the edge
+    /// </param>
+    /// <returns> If {@code to} is {@code null}, this method returns {@code null};
+    /// otherwise this method returns the result of calling <seealso cref="#addDFAState"/>
+    /// on {@code to} </returns>
+    virtual dfa::DFAState *addDFAEdge(dfa::DFA &dfa, dfa::DFAState *from, ssize_t t, dfa::DFAState *to);
+
+    /// <summary>
+    /// Add state {@code D} to the DFA if it is not already present, and return
+    /// the actual instance stored in the DFA. If a state equivalent to {@code D}
+    /// is already in the DFA, the existing state is returned. Otherwise this
+    /// method returns {@code D} after adding it to the DFA.
+    /// <p/>
+    /// If {@code D} is <seealso cref="#ERROR"/>, this method returns <seealso cref="#ERROR"/> and
+    /// does not change the DFA.
+    /// </summary>
+    /// <param name="dfa"> The dfa </param>
+    /// <param name="D"> The DFA state to add </param>
+    /// <returns> The state stored in the DFA. This will be either the existing
+    /// state if {@code D} is already in the DFA, or {@code D} itself if the
+    /// state was not already present. </returns>
+    virtual dfa::DFAState *addDFAState(dfa::DFA &dfa, dfa::DFAState *D);
+
+    virtual void reportAttemptingFullContext(dfa::DFA &dfa, const antlrcpp::BitSet &conflictingAlts,
+      ATNConfigSet *configs, size_t startIndex, size_t stopIndex);
+
+    virtual void reportContextSensitivity(dfa::DFA &dfa, size_t prediction, ATNConfigSet *configs,
+                                          size_t startIndex, size_t stopIndex);
+
+    /// If context sensitive parsing, we know it's ambiguity not conflict.
+    virtual void reportAmbiguity(dfa::DFA &dfa,
+                                 dfa::DFAState *D, // the DFA state from execATN() that had SLL conflicts
+                                 size_t startIndex, size_t stopIndex,
+                                 bool exact,
+                                 const antlrcpp::BitSet &ambigAlts,
+                                 ATNConfigSet *configs); // configs that LL not SLL considered conflicting
+
+  private:
+    // SLL, LL, or LL + exact ambig detection?
+    PredictionMode _mode;
+
+    static bool getLrLoopSetting();
+    void InitializeInstanceFields();
+  };
+
+} // namespace atn
+} // namespace antlr4
+