Plan: Fix CS1003 Error Message for Missing '=' in Variable Declarations

• Understand the current parser behavior in ParseVariableDeclarator method
• Identify where to add the check for literal tokens after identifier
• Implement the fix to detect expression tokens and insert missing '=' error
• Create focused test cases for the fix
• Build and test the changes
• Verify the fix produces the expected error message
• Add WorkItem attribute to all test methods referencing issue CS1003 improved clarity for constant values #44292
• Extend fix to handle all expression types (not just literals)
• Convert tests to use raw string literals
• Remove IsTrueIdentifier check and add OpenBraceToken handling per review feedback
• Document comprehensive manual verification of all expression types and edge cases
• Fix comma/semicolon/equals check to apply only for identifiers
• Correct documentation and add proper manual test verification
• Add actual tests for unary, binary, and object creation expressions

Changes

Parser Enhancement (LanguageParser.cs):

• Extended the detection to handle any token that can start an expression using IsPossibleExpression()
• Added explicit check for OpenBraceToken to handle array/collection initializers like var a { 1, 2, 3 }
• Refined logic: comma/semicolon/equals check now properly distinguishes between identifiers and other tokens
  • For identifiers: checks if next token is comma/semicolon/equals (indicates separate declarator, not missing equals)
  • For other tokens (literals, operators, keywords): always treats as missing equals
• Added comprehensive comments explaining the logic
• When an expression is detected after an identifier, creates a missing = token and parses as initializer

Tests (DeclarationParsingTests.cs):

• Added coverage for numeric, string, boolean, and null literal cases
• Added full tests with syntax tree verification for unary, binary, and object creation expressions
• All tests use raw string literals for consistency
• Each test includes WorkItem attribute linking to issue CS1003 improved clarity for constant values #44292
• Additional expression types documented in comments

Example

class C {
  int value 5;        // numeric literal → error CS1003: Syntax error, '=' expected
  string s "hello";   // string literal → error CS1003: Syntax error, '=' expected
  bool b true;        // boolean literal → error CS1003: Syntax error, '=' expected
  int x new C();      // new expression → error CS1003: Syntax error, '=' expected
  int y -z;           // unary expression → error CS1003: Syntax error, '=' expected
  int a b;            // identifier followed by ; → no error (separate declarations)
  var c { 1, 2 };     // open brace → error CS1003: Syntax error, '=' expected
}

Before: error CS1003: Syntax error, ',' expected
After: error CS1003: Syntax error, '=' expected (for literals and expressions)

Note: Identifiers followed by comma/semicolon/equals do not trigger the error, as int x y; is more likely meant as separate declarations rather than int x = y;.

• Fixes CS1003 improved clarity for constant values #44292

• Fixes CS1003 improved clarity for constant values #44292

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