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Static analysis & validation

Label validation

Naming rules

  • Must match pattern: [a-zA-Z_][a-zA-Z0-9_]*
  • Cannot be BASIC v2 keywords
  • Case-insensitive uniqueness within scope

Validation messages

error: line 5: label cannot start with a number: '1main'
error: line 8: label must start with a letter or underscore: '@label'
error: line 12: hyphens not allowed in labels: 'my-label'
error: line 15: special characters not allowed in labels: 'var$name'
error: line 20: label 'init' already defined in global scope

Duplicate detection

Labels must be unique within their scope:

init:
    print "first"
    return

init:
    print "second"
    return

Validation message

error: line 4: label 'init' already defined in global scope

Duplicates across different scopes are permitted:

task1: {
    init:
        print "first"
        return
}

task2: {
    init:
        print "second"
        return
}

Reference validation

All label references must resolve to defined labels:

main:
    gosub undefined_routine

Validation message

error: could not resolve label 'undefined_routine'

Label must be followed by code

Referenced labels must have BASIC code on the following line:

main:
    gosub helper

helper:
    rem Label exists but no code follows

Validation message

error: line 4: referenced label 'helper' not followed by basic code

This error occurs when a label is defined and referenced, but has no executable BASIC statement after it. Labels must point to actual code, not just comments or other labels.

Scope structure validation

Too many closing braces

Attempting to close a scope that doesn't exist:

main: {
    print "test"
}}

Validation message

error: unexpected '}' - no scope to close

Missing validation

BPP+ currently does not validate for missing closing braces at end of file. If you omit a closing brace, the parser may produce unexpected output or fail silently. Always ensure scopes are properly closed:

main: {
    print "test"
}    rem Always close your scopes!

Include validation

Include directives validated for:

  • File existence
  • File readability
  • Type validity (source or data only)
!include source "missing.bpp"

Validation message

error: line 1: include: file not found: 'missing.bpp'

!include invalid "file.bpp"

Validation message

error: line 1: include: unknown type: 'invalid'

See also