[ASDAlexander77]

Summary

A failure inside the generated ___unbox<C> was swallowed. <C>anyValue compiled into a cast that always throws "Can't cast from any type", and no error was shown. Two bugs combined:

• mlirGenInstanceOfOpaque reported failure as a null mlir::Value. ValueOrLogicalResult treats a null value as success with no value, so callers passed the failure on as a success. It now returns a ValueOrLogicalResult with a real failure on every path. Its internal EXIT_IF_FAILED_OR_NO_VALUE uses would have leaked "no value" the same way, so they are explicit failures now.

• A condition with no value was taken for success. if and while used EXIT_IF_FAILED_OR_NO_VALUE, which returns the value itself; do and for checked only for failure. The new conditionHasValue rejects a present condition that yields no value, with "the condition has no value". The message is postponed like every other one and shown only if compilation fails. On main, with a void call as the condition:

  statement	on main
  if	generated nothing (exit 0, no output); in ___unbox it dropped the if (a instanceof C) return a; test
  for	looped forever: no value is how for (;;) spells "no condition"
  do	segfaulted (null mlir::Value)
  while	failed with "empty block: expect at least a terminator"

  TypeScript also rejects testing a void value for truthiness.

Verification

• With a temporary forced failure in mlirGenInstanceOfOpaque, the untyped-catch cast, plain instanceof and instanceof narrowing all stop with the real error. The first of those used to compile into an always-throwing cast.
• New expected-error tests: test/tester/condition-value/{if,while,do,for}.ts. Each must print "the condition has no value", and must not print a stack dump or an assertion.
• Windows Release: 2847/2847 passed.
• Linux (WSL): 2841/2841 passed.

A correction to the note in #352: a failed generic instantiation does not leave its function in the module to be reused. The FuncOp is created detached and a failed body never reaches the module. The swallowing was entirely the two bugs above.

🤖 Generated with Claude Code