julia

9a437a52 - const lowering: respect scope, prohibit non-const `const` assignment

const lowering: respect scope, prohibit non-const `const` assignment Modifies the handling of the 3-argument "lowered const" so `const x = y` participates in scope resolution again (#56613); we treat (const x y) as an assignment form, producing the "unsupported `const` declaration on local variable" error if the usual scope rules would not make x global. At the top level, these should succeed: const x = 1 begin const x = 1 end let const global x = 1 end Each of the following should fail: # ERROR: syntax: unsupported `const` declaration on local variable around REPL[1]:2 let const x = 1 end # ERROR: syntax: unsupported `const` declaration on local variable around REPL[1]:2 function f() const x = 1 end This also amkes the use of `const global` inside a function body produce the original, specific error message rather than a generic "World age increment not at top level" error (#57334): # ERROR: syntax: `global const` declaration not allowed inside function around REPL[1]:2 function f() global const x = 1 end Issue #57334 revealed we silently accept `const` expressions writing to variables. These now fail with a new error message: a = [1, 2] # ERROR: syntax: cannot declare "a[1]" `const` around REPL[1]:2 const a[1] = 3 The bulk of these changes track const-ness through the functions called by expand-assignment, since each of the three types of LHS is affect differently: - ordinary variables become `const`, producing error if not global - `X{T} = ...` forces X to be `const`, rather than the defaulting to being implicitly const only if in global scope. - `f() = ...` ignores `const`.