That's not a particularly hard problem, all tools which try to solve it (for example, IntelliJ), solve it easily. For example, here's the syntax tree that rust-

That's not a particularly hard problem, all tools which try to solve it (for example, IntelliJ), solve it easily. For example, here's the syntax tree that rust-analyzer builds for this example: fn foo() { } fn fn bar() { } Syntax tree (whitespace nodes elided for clarity): SOURCE_FILE@[0; 31) FN_DEF@[0; 12) FN_KW@[0; 2) NAME@[3; 6) IDENT@[3; 6) "foo" ... FN_DEF@[14; 16) FN_KW@[14; 16) err: `expected a name` FN_DEF@[18; 30) FN_KW@[18; 20) NAME@[21; 24) IDENT@[21; 24) "bar" ... The problem is, a lot of tools are build with the assumption that the code is correct&complete, and don't try to tackle this problem at all.