From 815eff1f7c5c2fca63814f11fbf6e769bc599e38 Mon Sep 17 00:00:00 2001
From: "Alex Lam S.L" <alexlamsl@gmail.com>
Date: Fri, 1 Nov 2019 02:08:31 +0800
Subject: enhance `if_return` (#3560)

---
 lib/compress.js | 31 +++++++++++++++++++------------
 1 file changed, 19 insertions(+), 12 deletions(-)

(limited to 'lib/compress.js')

diff --git a/lib/compress.js b/lib/compress.js
index 65768c02..0321a532 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -1749,9 +1749,7 @@ merge(Compressor.prototype, {
                 if (stat instanceof AST_If) {
                     var ab = aborts(stat.body);
                     if (can_merge_flow(ab)) {
-                        if (ab.label) {
-                            remove(ab.label.thedef.references, ab);
-                        }
+                        if (ab.label) remove(ab.label.thedef.references, ab);
                         CHANGED = true;
                         stat = stat.clone();
                         stat.condition = stat.condition.negate(compressor);
@@ -1779,23 +1777,34 @@ merge(Compressor.prototype, {
                         }
                     }
 
-                    var ab = aborts(stat.alternative);
-                    if (can_merge_flow(ab)) {
-                        if (ab.label) {
-                            remove(ab.label.thedef.references, ab);
-                        }
+                    var alt = aborts(stat.alternative);
+                    if (can_merge_flow(alt)) {
+                        if (alt.label) remove(alt.label.thedef.references, alt);
                         CHANGED = true;
                         stat = stat.clone();
                         stat.body = make_node(AST_BlockStatement, stat.body, {
                             body: as_statement_array(stat.body).concat(extract_functions())
                         });
-                        var body = as_statement_array_with_return(stat.alternative, ab);
+                        var body = as_statement_array_with_return(stat.alternative, alt);
                         stat.alternative = make_node(AST_BlockStatement, stat.alternative, {
                             body: body
                         });
                         statements[i] = stat.transform(compressor);
                         continue;
                     }
+
+                    if (compressor.option("typeofs")) {
+                        if (ab && !alt) {
+                            mark_locally_defined(stat.condition, null, make_node(AST_BlockStatement, self, {
+                                body: statements.slice(i + 1)
+                            }));
+                        }
+                        if (!ab && alt) {
+                            mark_locally_defined(stat.condition, make_node(AST_BlockStatement, self, {
+                                body: statements.slice(i + 1)
+                            }));
+                        }
+                    }
                 }
 
                 if (stat instanceof AST_If && stat.body instanceof AST_Return) {
@@ -1940,9 +1949,7 @@ merge(Compressor.prototype, {
                             && loop_body(lct) === self
                         || stat instanceof AST_Continue
                             && loop_body(lct) === self) {
-                        if (stat.label) {
-                            remove(stat.label.thedef.references, stat);
-                        }
+                        if (stat.label) remove(stat.label.thedef.references, stat);
                     } else {
                         statements[n++] = stat;
                     }
-- 
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