[Bug Report] Compiler crashes when compiling all() on iterating over a heterogenouos tuple

[MetalOxideSemi]

Environment

• Codon version: v0.19.3
• OS: Debian bullseye

Description

Codon compiler crashes with a segmentation fault when compiling code that uses a generator expression with all() to iterate over a tuple of multiple class instances.

Steps to Reproduce

1. Code

class A:
    def __init__(self, a: int):
        self.a = a
    
    def filter(self, x: int) -> bool:
        return x % self.a == 0
    
class B:
    def __init__(self, b: float):
        self.b = b
        
    def filter(self, x: int) -> bool:
        return x % self.b == 0

class FilterCombiner:
    def __init__(self, *args):
        self.filters = tuple(args)

    def filter(self, x: int) -> bool:
        return all(f.filter(x) for f in self.filters)

fc = FilterCombiner(A(2), B(3.0))
fc.filter(1)

2. Run: ./codon run crash_on_filter.py

Expected Behavior

The code should compile and execute successfully, returning the result of the filter operation.

Actual Behavior

The compiler crashes with a segmentation fault:

[1]    1803306 segmentation fault (core dumped)  ./codon run temp/crash_on_filter.py

Debug Information

Using GDB, the crash occurs at:

Program received signal SIGSEGV, Segmentation fault.
codon::ast::TypecheckVisitor::visit (this=0x7fffffff7dd0, expr=0xe2af2f0)
    at codon/parser/visitors/typecheck/collections.cpp:144

Stack trace:

#0  codon::ast::TypecheckVisitor::visit (this=0x7fffffff7dd0, expr=0xe2af2f0)
    at codon/parser/visitors/typecheck/collections.cpp:144

Root cause location:
File: codon/parser/visitors/typecheck/collections.cpp:144

Function:

Expr *GeneratorExpr::getFinalExpr() {
  auto s = *(getFinalStmt());
  if (cast<ExprStmt>(s))
    return cast<ExprStmt>(s)->getExpr();
  return nullptr;
}

GDB inspection:

(gdb) p expr
$1 = (codon::ast::GeneratorExpr *) 0xe2af2f0

(gdb) p expr->getFinalExpr()
$2 = (codon::ast::Expr *) 0x0

The issue appears to be that getFinalExpr() returns nullptr, which is then dereferenced, causing the segmentation fault.

The crash occurs during type checking of the generator expression (f.filter(x) for f in self.filters) when used with all(). The GeneratorExpr::getFinalExpr() returns null, suggesting the generator expression's final statement is not properly initialized or handled during type checking when dealing with heterogeneous class types (A and B) stored in a tuple.