Replace ANTLR with hand-rolled parser (#917)

Co-authored-by: Kushal Pisavadia <kushi.p@gmail.com>
Co-authored-by: Daniel Chao <daniel.h.chao@gmail.com>

docs/modules/language-reference/pages/index.adoc

@@ -3196,7 +3196,6 @@ This section discusses language features that are generally more relevant to tem
 <<glob-patterns,Glob Patterns>> +
 <<doc-comments,Doc Comments>> +
 <<name-resolution,Name Resolution>> +
-<<grammar-definition,Grammar Definition>> +
 <<reserved-keywords,Reserved Keywords>> +
 <<blank-identifiers,Blank Identifiers>> +
 <<projects,Projects>> +
@@ -5274,11 +5273,6 @@ For example, the prototype chain of value `42` contains, now listed from top to
 
 A prototype chain never contains a non-object value, such as `42`.
 
-[[grammar-definition]]
-=== Grammar Definition
-
-Pkl's link:{uri-antlr4}[ANTLR 4] grammar is defined in link:{uri-github-PklLexer}[PklLexer.g4] and link:{uri-github-PklParser}[PklParser.g4].
-
 [[reserved-keywords]]
 === Reserved keywords
 

docs/src/test/kotlin/DocSnippetTests.kt

@@ -16,15 +16,14 @@ import org.pkl.core.Loggers
 import org.pkl.core.SecurityManagers
 import org.pkl.core.StackFrameTransformers
 import org.pkl.core.module.ModuleKeyFactories
-import org.pkl.core.parser.LexParseException
-import org.pkl.core.parser.Parser
-import org.pkl.core.parser.antlr.PklParser
 import org.pkl.core.repl.ReplRequest
 import org.pkl.core.repl.ReplResponse
 import org.pkl.core.repl.ReplServer
 import org.pkl.core.util.IoUtils
-import org.antlr.v4.runtime.ParserRuleContext
 import org.pkl.core.http.HttpClient
+import org.pkl.core.parser.Parser
+import org.pkl.core.parser.ParserError
+import org.pkl.core.parser.ast.ClassProperty
 import org.pkl.core.resource.ResourceReaders
 import java.nio.file.Files
 import kotlin.io.path.isDirectory
@@ -303,7 +302,7 @@ class DocSnippetTestsEngine : HierarchicalTestEngine<DocSnippetTestsEngine.Execu
 
       override fun getType() = Type.TEST
 
-      private val parsed: ParserRuleContext by lazy {
+      private val parsed: org.pkl.core.parser.ast.Node by lazy {
         when (language) {
           "pkl" -> Parser().parseModule(code)
           "pkl-expr" -> Parser().parseExpressionInput(code)
@@ -318,7 +317,7 @@ class DocSnippetTestsEngine : HierarchicalTestEngine<DocSnippetTestsEngine.Execu
             if (expectError) {
               throw AssertionError("Expected a parse error, but got none.")
             }
-          } catch (e: LexParseException) {
+          } catch (e: ParserError) {
             if (!expectError) {
               throw AssertionError(e.message)
             }
@@ -335,7 +334,7 @@ class DocSnippetTestsEngine : HierarchicalTestEngine<DocSnippetTestsEngine.Execu
           )
         )
 
-        val properties = parsed.children.filterIsInstance<PklParser.ClassPropertyContext>()
+        val properties = parsed.children()?.filterIsInstance<ClassProperty>() ?: emptyList()
 
         val responses = mutableListOf<ReplResponse>()
 
@@ -344,7 +343,7 @@ class DocSnippetTestsEngine : HierarchicalTestEngine<DocSnippetTestsEngine.Execu
           responses.addAll(context.replServer.handleRequest(
             ReplRequest.Eval(
               "snippet",
-              prop.Identifier().text,
+              prop.name.value,
               false,
               true
             )