public SemanticContext evalPrecedence(Recognizer<?,?> parser, RuleContext parserCallStack) {
		return this;
	}
Evaluate the precedence predicates for the context and reduce the result.

@param parser The parser instance.
@param parserCallStack
@return The simplified semantic context after precedence predicates are
evaluated, which will be one of the following values.
<ul>
<li>{@link Empty#Instance}: if the predicate simplifies to {@code true} after
precedence predicates are evaluated.</li>
<li>{@code null}: if the predicate simplifies to {@code false} after
precedence predicates are evaluated.</li>
<li>{@code this}: if the semantic context is not changed as a result of
precedence predicate evaluation.</li>
<li>A non-{@code null} {@link SemanticContext}: the new simplified
semantic context after precedence predicates are evaluated.</li>
</ul>
runtime/Java/src/org/antlr/v4/runtime/atn/SemanticContext.java