Three compiler additions, exercised end-to-end by testpunit2.pas:
* Default parameter values — single-name, non-var, non-open-array params
may carry '= literal-or-named-constant'. Overload resolution accepts
any arity in [MinArity, ParamCount]; the resolver tie-breaks toward
the candidate that needs fewer defaulted slots. AnalyseProcCall and
AnalyseFuncCallExpr clone the default expression into the call's Args
list. Defaults declared on a unit-interface forward decl are
ownership-transferred to the matching impl param at reconciliation.
* Metaclass references — a bare class type identifier in a value
position (e.g. 'EError' as an argument or in 'Pointer(EError)') is
now retyped to Pointer with codegen emitting '$typeinfo_<Name>' as
an immediate. Matches the value held by vtable[0], so 'A.ClassType =
EError' is true exactly when A is an instance of that exact class.
* Numeric widening at call sites — the existing CoerceArg helper now
covers Integer→Double (swtof/sltof), Single→Double (exts) and
Integer→Single, in addition to the pre-existing w→l. Inherited-,
constructor-, method-, and function-call sites all route through it.
punit.pas gains DefaultDoubleDelta, two Double AssertEquals overloads,
and '= ''' defaults on the four-arity AddTest declarations.
Docs: grammar.ebnf extends ParamGroup with the optional default; a new
DefaultValue rule lists the permitted forms. language-rationale.adoc
adds 'Default Parameter Values' and 'Metaclass References' sections
recording the decision, alternatives rejected, and the overload
tie-break formula.
All 1194 existing compiler tests pass; testpunit2 compiles, assembles,
links and runs (31 tests; the expected pass/fail/inactive pattern).
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