"I think that Mozilla's Rust is aiming squarely at C++ developers, whereas Go is more of a Java replacement."
I basically agree with this as a Rust developer (although I'm not sure about Go being in Java's niche; I think of it more as in node.js's niche -- highly scalable web apps). Early on, I think both Rust and Go were thought to be targeting the same segment, but it turned out that we really weren't. Personally, I'm completely fine with that; different language designs are appropriate for different roles. The huge amount of work that we've done to make non-allocating and manually-memory-managed code easy, predictable, and type-safe is totally overkill for Go's niche, for example, while for games and web browsers this sort of thing is essential.
I basically agree with this as a Rust developer (although I'm not sure about Go being in Java's niche; I think of it more as in node.js's niche -- highly scalable web apps). Early on, I think both Rust and Go were thought to be targeting the same segment, but it turned out that we really weren't. Personally, I'm completely fine with that; different language designs are appropriate for different roles. The huge amount of work that we've done to make non-allocating and manually-memory-managed code easy, predictable, and type-safe is totally overkill for Go's niche, for example, while for games and web browsers this sort of thing is essential.