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[CSharp] Parsing source with syntax error causes ClassCastExceptin #2612

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yososs opened this issue May 6, 2022 · 6 comments
Closed

[CSharp] Parsing source with syntax error causes ClassCastExceptin #2612

yososs opened this issue May 6, 2022 · 6 comments
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csharp

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@yososs
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yososs commented May 6, 2022 •
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I found this to be a cast error when entering the wrong C++ syntax into CSharp's parser.
This does not appear to be the correct way to handle syntax errors.

Sources containing syntax error

class A{
  void a() {
    int[] nums = {1, 3, 5, 7};
    for (int num : nums){
        b(num);
    }
  }
}

Added the following cast check to avoid cast errors in CSharpParserBase.java.

public abstract class CSharpParserBase extends Parser
{
    protected CSharpParserBase(TokenStream input)
    {
	super(input);
    }

    protected boolean IsLocalVariableDeclaration()
    {
   // fix
    if (!(this._ctx instanceof CSharpParser.Local_variable_declarationContext)) {
    	return false;
    }

	CSharpParser.Local_variable_declarationContext local_var_decl = (CSharpParser.Local_variable_declarationContext)this._ctx;
	if (local_var_decl == null) return true;
	CSharpParser.Local_variable_typeContext local_variable_type = local_var_decl.local_variable_type();
	if (local_variable_type == null) return true;
	if (local_variable_type.getText().equals("var")) return false;
	return true;
    }
}

However, it should be a syntax error, but it is not a syntax error.
Few people may consider this use case important.
Maybe it should be managed as a separate issue.
@KvanTTT KvanTTT added the csharp label May 6, 2022
@kaby76
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kaby76 commented May 7, 2022

The grammars-v4/csharp/ parser gives a syntax error for that input:

# run in Bash shell.
git clone https://github.com/antlr/grammars-v4.git
cd grammars-v4/csharp
trgen
cd Generated
make
cat - << HERE > test.in
class A{
  void a() {
    int[] nums = {1, 3, 5, 7};
    for (int num : nums){
        b(num);
    }
  }
}
HERE
dotnet run -file test.in

Output:

line 4:17 mismatched input ':' expecting ';'
Time: 00:00:00.1457023
Parse failed.

Please clarify what you are trying to do.

@yososs
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yososs commented May 7, 2022 •
edited
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I am intentionally entering source code that results in a syntax error. The expected result is that CSharpParser reports a syntax error.

  1. the actual result is that ClassCastException is thrown
  2. if I fix this problem by adding a cast check, no syntax error is reported

2 is a pointing error, as I found a problem with my checking method.

To reproduce 1, follow the steps

You need to test on a java target.

  1. save the above source in examples/test.cs
  2. mvn3 test
Caused by: java.lang.ClassCastException: class CSharpParser$Local_variable_declaratorContext cannot be cast to class CSharpParser$Local_variable_declarationContext (CSharpParser$Local_variable_declaratorContext and CSharpParser$Local_variable_declarationContext are in unnamed module of loader java.net.URLClassLoader @6570e3cb)
	at CSharpParserBase.IsLocalVariableDeclaration(CSharpParserBase.java:13)
	at CSharpParser.local_variable_declaration_sempred(CSharpParser.java:20502)
	at CSharpParser.sempred(CSharpParser.java:20489)
	at org.antlr.v4.runtime.atn.SemanticContext$Predicate.eval(SemanticContext.java:94)
	at org.antlr.v4.runtime.atn.ParserATNSimulator.evalSemanticContext(ParserATNSimulator.java:1430)
	at org.antlr.v4.runtime.atn.ParserATNSimulator.splitAccordingToSemanticValidity(ParserATNSimulator.java:1346)
	at org.antlr.v4.runtime.atn.ParserATNSimulator.getSynValidOrSemInvalidAltThatFinishedDecisionEntryRule(ParserATNSimulator.java:1301)
	at org.antlr.v4.runtime.atn.ParserATNSimulator.execATN(ParserATNSimulator.java:469)
	at org.antlr.v4.runtime.atn.ParserATNSimulator.adaptivePredict(ParserATNSimulator.java:393)
	at CSharpParser.local_variable_declarator(CSharpParser.java:9577)
	at CSharpParser.local_variable_declaration(CSharpParser.java:9434)
	at CSharpParser.for_initializer(CSharpParser.java:10278)
	at CSharpParser.simple_embedded_statement(CSharpParser.java:8896)
	at CSharpParser.embedded_statement(CSharpParser.java:8223)
	at CSharpParser.statement(CSharpParser.java:7626)
	at CSharpParser.statement_list(CSharpParser.java:10209)
	at CSharpParser.block(CSharpParser.java:9287)
	at CSharpParser.method_body(CSharpParser.java:13611)
	at CSharpParser.method_declaration(CSharpParser.java:19943)
	at CSharpParser.common_member_declaration(CSharpParser.java:12900)
	at CSharpParser.class_member_declaration(CSharpParser.java:12608)
	at CSharpParser.class_member_declarations(CSharpParser.java:12467)
	at CSharpParser.class_body(CSharpParser.java:12408)
	at CSharpParser.class_definition(CSharpParser.java:18904)
	at CSharpParser.type_declaration(CSharpParser.java:11539)
	at CSharpParser.namespace_member_declaration(CSharpParser.java:11447)
	at CSharpParser.namespace_member_declarations(CSharpParser.java:11361)
	at CSharpParser.compilation_unit(CSharpParser.java:421)
	... 31 more

Modifying CShapParserBase.java reports the following syntax error

line 4:17 mismatched input ':' expecting {'add', 'alias', '__arglist', 'ascending', 'async', 'await', 'by', 'descending', 'dynamic', 'equals', 'from', 'get', 'group', 'into', 'join', 'let', 'nameof', 'on', 'orderby', 'partial', 'remove', 'select', 'set', 'unmanaged', 'var', 'when', 'where', 'yield', IDENTIFIER, '[', '*', '?'}
com.khubla.antlr.antlr4test.AssertErrorsException: found 1 errors, but missing file test.cs.errors
	at com.khubla.antlr.antlr4test.AssertErrorsErrorListener.assertErrors(AssertErrorsErrorListener.java:64)
	at com.khubla.antlr.antlr4test.ScenarioExecutor.testGrammar(ScenarioExecutor.java:174)
	at com.khubla.antlr.antlr4test.ScenarioExecutor.testGrammars(ScenarioExecutor.java:229)
	at com.khubla.antlr.antlr4test.GrammarTestMojo.testScenarios(GrammarTestMojo.java:360)
	at com.khubla.antlr.antlr4test.GrammarTestMojo.execute(GrammarTestMojo.java:179)
	at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:137)
	at org.apache.maven.lifecycle.internal.MojoExecutor.doExecute(MojoExecutor.java:301)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:211)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:165)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:157)
	at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:121)
	at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:81)
	at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build(SingleThreadedBuilder.java:56)
	at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:127)
	at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:294)
	at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:192)
	at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:105)
	at org.apache.maven.cli.MavenCli.execute(MavenCli.java:960)
	at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:293)
	at org.apache.maven.cli.MavenCli.main(MavenCli.java:196)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:78)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:567)
	at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:282)
	at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:225)
	at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:406)
	at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:347)

@kaby76
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kaby76 commented May 7, 2022

Got it. Yes, it doesn't work.

@yososs
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yososs commented May 7, 2022

I am concerned about the different syntax error messages when run with dotnet and when run with java.

dotnet

line 4:17 mismatched input ':' expecting ';'

java

line 4:17 mismatched input ':' expecting {'add', 'alias', '__arglist', 'ascending', 'async', 'await', 'by', 'descending', 'dynamic', 'equals', 'from', 'get', 'group', 'into', 'join', 'let', 'nameof', 'on', 'orderby', 'partial', 'remove', 'select', 'set', 'unmanaged', 'var', 'when', 'where', 'yield', IDENTIFIER, '[', '*', '?'}

@kaby76
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kaby76 commented May 7, 2022

I agree. I have a PR to fix the cast problem, but we'll need to find out why the diff in the runtimes.

This was referenced May 7, 2022
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@yososs
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yososs commented May 7, 2022

Close this issue after confirming the merge.

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@KvanTTT @yososs @kaby76