Single-statement for loop causes panic

[jlapeyre]

Version 0.4.0

These methods look for either a single statement or a body. If the body is not found, it should return None.

openqasm3_parser/crates/oq3_syntax/src/ast/generated/nodes.rs

Lines 270 to 275 in 22b55cc

	pub fn body(&self) -> Option<BlockExpr> {
	support::child(&self.syntax)
	}
	pub fn stmt(&self) -> Option<Stmt> {
	support::child(&self.syntax)
	}

But when constructing the ASG, the final representation of the OQ3 program, we erroneously assume that the for statement loops over a block and never over a single statement:

openqasm3_parser/crates/oq3_semantics/src/syntax_to_semantics.rs

Line 245 in 22b55cc

let loop_body = from_block_expr(for_stmt.body().unwrap(), context);

In case there is no block, the unwrap causes a panic.