- `side_effects` will clean up inner statements, so checking for an empty function body should suffice
- drop side effects when dropping `return` from statement
- move these optimisations out from `Compressor` to `OutputStream`
- fixes behaviour inconsistency when running uglified code from global or module levels due to redefinition
When fixing catch-related issue in #1715, it tries to optimise for duplicate definitions but did not take anonymous functions into account.
Remove such optimisation for now and we can cover this as a more general rule later.
`statement_to_expression()` drops `typeof` even if it operates on undeclared variables.
Since we now have `drop_side_effect_free()`, replace and remove this deprecated functionality.
Unlike normal variables and even function definitions, these cannot be reassigned, even though assignment expressions would "leak" the assigned value as normal.
Process variable definitions with or without assigned values against:
- `arguments`
- named function arguments
- multiple definitions within same scope
Essentially demote variable declarations with no value assignments.
Also fixed invalid use of `AST_VarDef` over `arguments` - should use a member of `AST_SymbolDeclaration` instead.
Conditions including strict mode would make `delete` return `true` or `false`, and are too complex to be evaluated by the compressor.
Suppress assignment folding into said operator.
fixes#1685
`AST_Try` is an `AST_Block`, so besides try block we also need to inspect catch and finally blocks for possible side effects.
Also extend this functionality to handle `AST_If` and `AST_LabeledStatement` while we are at it.
fixes#1673
Turns out the only place in `Compressor` which can generate invalid `AST_For.init` is within `drop_unused()`, so focus the fix-up efforts.
supercedes #1652fixes#1656
- #1634 bars variables with cross-scope references in between to collapse
- but if assigned value is side-effect-free, no states can be modified, so it is safe to move
The following is wrong:
`a == (b ? a : c)` => `b`
Because:
- `b` may not be boolean
- `a` might have side effects
- `a == a` is not always `true` (think `NaN`)
- `a == c` is not always `false`
`reduce_vars` enables substitution of variables but did not clone the value's `AST_Node`.
This confuses `collapse_vars` and result in invalid AST and subsequent crash.
fixes#1609
As patched in #1597, `make_node_from_constant()` makes inconsistent and sometimes incorrect calls to `optimize()` and `transform()`.
Fix those issues properly by changing the semantics of `evaluate()` and `make_node_from_constant()`, with the side effect that `evaluate()` no longer eagerly converts constant to `AST_Node`.
Liberal use of `Compressor.transform()` and `AST_Node.optimize()` presents an issue for look-up operations like `TreeWalker.in_boolean_context()` and `TreeWalker.parent()`.
This is an incremental fix such that `AST_Node.optimize()` would now contain the correct stack information when called correctly.
Self-referenced function has non-fixed values assigned to its parameters.
Let `unused` & `!keep_fnames` do the scanning, then apply `reduce_vars` only to unnamed functions.
fixes#1595
- one-use function call => IIFE should take `eval()` & `arguments` into account
- if unused parameter cannot be eliminated, replace it with `0`
fixes#1583
those were not optimised for `unused` before, which made it necessary for `reduce_vars` to have separate steps for `keep_fnames`
docs update by @kzc
closes#1577
Function expression can be assigned to a variable and be given a name. Ensure function name is the reduced variable before clearing it out.
fixes#1573fixes#1575
