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fix corner case in unused (#4559)
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fixes #4558
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@alexlamsl
alexlamsl authored Jan 15, 2021
1 parent 18dbceb commit 74368c3
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Showing 2 changed files with 89 additions and 36 deletions.
74 changes: 38 additions & 36 deletions lib/compress.js
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Original file line number Diff line number Diff line change
Expand Up @@ -5453,6 +5453,7 @@ merge(Compressor.prototype, {
var in_use_ids = Object.create(null); // avoid expensive linear scans of in_use
var value_read = Object.create(null);
var value_modified = Object.create(null);
var var_defs = Object.create(null);
if (self instanceof AST_Toplevel && compressor.top_retain) {
self.variables.each(function(def) {
if (compressor.top_retain(def) && !(def.id in in_use_ids)) {
Expand All @@ -5462,7 +5463,6 @@ merge(Compressor.prototype, {
});
}
var assignments = new Dictionary();
var var_defs_by_id = new Dictionary();
var initializations = new Dictionary();
// pass 1: find out which symbols are directly used in
// this scope (not in nested scopes).
Expand Down Expand Up @@ -5495,10 +5495,10 @@ merge(Compressor.prototype, {
defn.name.mark_symbol(function(name) {
if (!(name instanceof AST_SymbolDeclaration)) return;
var def = name.definition();
var_defs_by_id.add(def.id, defn);
var_defs[def.id] = (var_defs[def.id] || 0) + 1;
if (node instanceof AST_Var && def.orig[0] instanceof AST_SymbolCatch) {
var redef = def.redefined();
if (redef) var_defs_by_id.add(redef.id, defn);
if (redef) var_defs[redef.id] = (var_defs[redef.id] || 0) + 1;
}
if (!(def.id in in_use_ids) && (!drop_vars
|| (node instanceof AST_Const ? def.redefined() : def.const_redefs)
Expand All @@ -5518,7 +5518,7 @@ merge(Compressor.prototype, {
}
if (node instanceof AST_SymbolFunarg) {
var def = node.definition();
var_defs_by_id.add(def.id, node);
var_defs[def.id] = (var_defs[def.id] || 0) + 1;
assignments.add(def.id, node);
return true;
}
Expand Down Expand Up @@ -5577,6 +5577,7 @@ merge(Compressor.prototype, {
});
};
// pass 3: we should drop declarations not in_use
var trim_defns = [];
var unused_fn_names = [];
var calls_to_drop_args = [];
var fns_with_marked_args = [];
Expand Down Expand Up @@ -5743,8 +5744,9 @@ merge(Compressor.prototype, {
var is_var = node instanceof AST_Var;
node.definitions.forEach(function(def) {
if (def.value) def.value = def.value.transform(tt);
var value = def.value;
if (def.name instanceof AST_Destructured) {
var name = trim_destructured(def.name, def.value, function(node) {
var name = trim_destructured(def.name, value, function(node) {
if (!drop_vars) return node;
if (node.definition().id in in_use_ids) return node;
if (is_catch(node)) return node;
Expand All @@ -5754,56 +5756,54 @@ merge(Compressor.prototype, {
if (name) {
flush();
} else {
var value = def.value.drop_side_effect_free(compressor);
value = value.drop_side_effect_free(compressor);
if (value) side_effects.push(value);
}
return;
}
var sym = def.name.definition();
var drop_sym = is_var ? can_drop_symbol(def.name) : is_safe_lexical(sym);
if (!drop_sym || !drop_vars || sym.id in in_use_ids) {
if (def.value && indexOf_assign(sym, def) < 0) {
var write_only = def.value.write_only;
var value = def.value.drop_side_effect_free(compressor);
if (value && indexOf_assign(sym, def) < 0) {
var write_only = value.write_only;
value = value.drop_side_effect_free(compressor);
if (def.value !== value) {
sym.references.forEach(function(node) {
if (node.fixed === sym.fixed) node.fixed = def.value;
});
def.value = null;
if (value) {
AST_Node.warn("Side effects in last use of variable {name} [{file}:{line},{col}]", template(def.name));
side_effects.push(value);
}
} else if (def.value.write_only !== write_only) {
def.value.write_only = write_only;
value = null;
trim_defns.push(def);
} else if (value.write_only !== write_only) {
value.write_only = write_only;
}
}
var old_def, var_defs = var_defs_by_id.get(sym.id);
if (!def.value && !(node instanceof AST_Let)) {
if (drop_sym && var_defs.length > 1) {
var old_def;
if (!value && !(node instanceof AST_Let)) {
if (drop_sym && var_defs[sym.id] > 1) {
AST_Node.info("Dropping declaration of variable {name} [{file}:{line},{col}]", template(def.name));
remove(var_defs, def);
var_defs[sym.id]--;
sym.eliminated++;
} else {
head.push(def);
}
} else if (compressor.option("functions")
&& !compressor.option("ie8")
&& !(node instanceof AST_Const || node instanceof AST_Let)
&& var_defs.length == 1
&& var_defs[sym.id] == 1
&& sym.assignments == 0
&& def.value instanceof AST_Function
&& value instanceof AST_Function
&& (sym.references.length ? all(sym.references, function(ref) {
return def.value === ref.fixed_value();
}) : def.value === def.name.fixed_value())
&& (!def.value.name || (old_def = def.value.name.definition()).assignments == 0
return value === ref.fixed_value();
}) : value === def.name.fixed_value())
&& (!value.name || (old_def = value.name.definition()).assignments == 0
&& (old_def.name == def.name.name || all(old_def.references, function(ref) {
return ref.scope.find_variable(def.name.name) === def.name.definition();
})))
&& can_declare_defun()
&& can_rename(def.value, def.name.name)) {
&& can_rename(value, def.name.name)) {
AST_Node.warn("Declaring {name} as function [{file}:{line},{col}]", template(def.name));
var defun = make_node(AST_Defun, def, def.value);
var defun = make_node(AST_Defun, def, value);
defun.name = make_node(AST_SymbolDefun, def.name, def.name);
var name_def = def.name.scope.resolve().def_function(defun.name);
if (old_def) old_def.forEach(function(node) {
Expand All @@ -5813,26 +5813,25 @@ merge(Compressor.prototype, {
});
body.push(defun);
} else {
if (drop_sym && var_defs.length > 1 && sym.orig.indexOf(def.name) > sym.eliminated) {
remove(var_defs, def);
if (drop_sym && var_defs[sym.id] > 1 && sym.orig.indexOf(def.name) > sym.eliminated) {
var_defs[sym.id]--;
duplicated++;
}
flush();
}
} else if (is_catch(def.name)) {
var value = def.value && def.value.drop_side_effect_free(compressor);
value = value && value.drop_side_effect_free(compressor);
if (value) side_effects.push(value);
var var_defs = var_defs_by_id.get(sym.id);
if (var_defs.length > 1) {
if (var_defs[sym.id] > 1) {
AST_Node.warn("Dropping duplicated declaration of variable {name} [{file}:{line},{col}]", template(def.name));
remove(var_defs, def);
var_defs[sym.id]--;
sym.eliminated++;
} else {
def.value = null;
head.push(def);
}
} else {
var value = def.value && !def.value.single_use && def.value.drop_side_effect_free(compressor);
value = value && !value.single_use && value.drop_side_effect_free(compressor);
if (value) {
AST_Node.warn("Side effects in initialization of unused variable {name} [{file}:{line},{col}]", template(def.name));
side_effects.push(value);
Expand Down Expand Up @@ -5865,9 +5864,9 @@ merge(Compressor.prototype, {
body.push(make_node(AST_SimpleStatement, node, {
body: make_sequence(node, side_effects)
}));
} else if (def.value) {
side_effects.push(def.value);
def.value = make_sequence(def.value, side_effects);
} else if (value) {
side_effects.push(value);
def.value = make_sequence(value, side_effects);
} else {
def.value = make_node(AST_UnaryPrefix, def, {
operator: "void",
Expand Down Expand Up @@ -6017,6 +6016,9 @@ merge(Compressor.prototype, {
&& self.body[0].value == "use strict") {
self.body.length = 0;
}
trim_defns.forEach(function(def) {
def.value = null;
});
unused_fn_names.forEach(function(fn) {
fn.name = null;
});
Expand Down
51 changes: 51 additions & 0 deletions test/compress/drop-unused.js
View file
Original file line number Diff line number Diff line change
Expand Up @@ -3197,3 +3197,54 @@ issue_4464_3: {
"function",
]
}

issue_4558_1: {
options = {
evaluate: true,
pure_getters: true,
reduce_vars: true,
sequences: true,
side_effects: true,
toplevel: true,
unused: true,
}
input: {
var a = 0;
var b = 1, b = c >>>= a;
var c = 0;
b && 0[a++],
console.log(a);
}
expect: {
var a = 0;
var b = c >>>= a;
var c;
b && a++,
console.log(a);
}
expect_stdout: "0"
}

issue_4558_2: {
options = {
evaluate: true,
ie8: true,
reduce_vars: true,
unused: true,
}
input: {
(function() {
var a = 1;
var b = (a = NaN) || (console.log("PASS"), 2);
return a;
})();
}
expect: {
(function() {
var a;
(a = NaN) || console.log("PASS");
return a;
})();
}
expect_stdout: "PASS"
}

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