Sway follows the design philosophies of Rust and Solidity, with some Fuel ideology mixed in. From Solidity, we took the notion of smart contract programming as a paradigm. This led to storage blocks, contract ABIs as entry points, etc.
From Rust, we took the prioritizations of performance, control, and safety. In Rust, this means the borrow checker, safe parallelism (send and sync), annotated unsafety, etc., mainly to save the programmer from referencing freed memory, shared mutable state, and undesirable memory management. This is great for a general-purpose language model. Sway, however, is not general purpose. Sway targets a blockchain VM environment, where execution is not indefinite, and memory allocation and management are less concerned. Instead, we need to optimize for gas costs and contract-level safety. We applied the philosophy of performance, control, and safety and interpreted it in this new context. This is where Sway gets compile time checks of state mutability, namespacing of state variables, static analysis passes, and gas profiling/optimization.