Parse error recovery

[obiwan87]

When typing code, it is normal that the syntax/grammar enters a non-correct state. For example, think of the following snippets

• selecting an identifier x.<missing>
• writing an if block "if "
• etc.

In IntellIJ, when a parse error is encountered, the parser stops and the rest of the text will not be parsed. This leads to

• semantic highlighting not working or flickering colors
• errors being reported in an unexpected location
• pollution of Psi-Tree makes with DUMMY-Block + Error

It is therefore necessary to define rules for the parser, that tell it how to recover from incomplete statements and expressions, such that the error will be contained in a small region of the code.

Write recover rules for the following statements, expressions and types:

• package declaration statement
• variable declaration statement
• variable initialization statement
• assignment statement
• if statement
• switch statement
• case-clauses
• struct fields
• for statement (probably need to merge rules for "for" and "for ... in ..."
• binary expressions
• selector expression
• argument list
• parameter list
• proc, enum, struct, union, bit_field, ...
• where-clause
• unclosed blocks (consume unclosed block until beginning of next block owner, I guess)
• statement list (when statement list breaks, error is wrongly shown before the begin of the block)
• list of procedures inside procedure group (use list with recovery)
• when statement
  ...

[obiwan87]

Check for null after recover rules is introduced, as mandatory elements could become optional