From c5496ff4e5436a9d82d7e568fb6e14df3009d635 Mon Sep 17 00:00:00 2001
From: Nick Treleaven <ntrel002@gmail.com>
Date: Sat, 17 Aug 2024 10:05:52 +0100
Subject: [PATCH] Fix Bugzilla 24706 - Missing errors for first operand of
 comma expression (#16787)

---
 compiler/src/dmd/expressionsem.d          | 13 ++++++++-----
 compiler/test/fail_compilation/misc1.d    | 17 ++++++++++-------
 compiler/test/fail_compilation/must_use.d |  7 +++++--
 3 files changed, 23 insertions(+), 14 deletions(-)

diff --git a/compiler/src/dmd/expressionsem.d b/compiler/src/dmd/expressionsem.d
index 8e0c9adf77a1..9c46ecca20d8 100644
--- a/compiler/src/dmd/expressionsem.d
+++ b/compiler/src/dmd/expressionsem.d
@@ -9824,13 +9824,16 @@ private extern (C++) final class ExpressionSemanticVisitor : Visitor
         if (sc.inCfile)
             return;
 
-        if (e.type is Type.tvoid)
+        if (!e.isGenerated)
         {
-            checkMustUse(e.e1, sc);
-            discardValue(e.e1);
+            if (e.allowCommaExp)
+            {
+                checkMustUse(e.e1, sc);
+                discardValue(e.e1);
+            }
+            else
+                error(e.loc, "using the result of a comma expression is not allowed");
         }
-        else if (!e.allowCommaExp && !e.isGenerated)
-            error(e.loc, "using the result of a comma expression is not allowed");
     }
 
     override void visit(IntervalExp e)
diff --git a/compiler/test/fail_compilation/misc1.d b/compiler/test/fail_compilation/misc1.d
index 21d02cdae449..95bcc6d03d47 100644
--- a/compiler/test/fail_compilation/misc1.d
+++ b/compiler/test/fail_compilation/misc1.d
@@ -1,13 +1,14 @@
 /*
 TEST_OUTPUT:
 ---
-fail_compilation/misc1.d(108): Error: `5` has no effect
-fail_compilation/misc1.d(109): Error: `1 + 2` has no effect
-fail_compilation/misc1.d(115): Deprecation: `1 * 1` has no effect
-fail_compilation/misc1.d(116): Deprecation: `__lambda3` has no effect
-fail_compilation/misc1.d(122): Deprecation: `false` has no effect
-fail_compilation/misc1.d(125): Deprecation: `*sp++` has no effect
-fail_compilation/misc1.d(126): Deprecation: `j` has no effect
+fail_compilation/misc1.d(109): Error: `5` has no effect
+fail_compilation/misc1.d(110): Error: `1 + 2` has no effect
+fail_compilation/misc1.d(111): Error: `x` has no effect
+fail_compilation/misc1.d(117): Deprecation: `1 * 1` has no effect
+fail_compilation/misc1.d(118): Deprecation: `__lambda3` has no effect
+fail_compilation/misc1.d(124): Deprecation: `false` has no effect
+fail_compilation/misc1.d(127): Deprecation: `*sp++` has no effect
+fail_compilation/misc1.d(128): Deprecation: `j` has no effect
 ---
 */
 
@@ -20,8 +21,10 @@ void hasSideEffect12490(){}
 
 void issue12490()
 {
+    int x;
     5, hasSideEffect12490();
     1 + 2, hasSideEffect12490();
+    x, x++;
 }
 
 void issue23480()
diff --git a/compiler/test/fail_compilation/must_use.d b/compiler/test/fail_compilation/must_use.d
index e3b5fedfd4d7..f21c4a405d5e 100644
--- a/compiler/test/fail_compilation/must_use.d
+++ b/compiler/test/fail_compilation/must_use.d
@@ -1,16 +1,19 @@
 /+
 TEST_OUTPUT:
 ---
-fail_compilation/must_use.d(15): Error: ignored value of `@mustuse` type `must_use.S`; prepend a `cast(void)` if intentional
+fail_compilation/must_use.d(17): Error: ignored value of `@mustuse` type `must_use.S`; prepend a `cast(void)` if intentional
+fail_compilation/must_use.d(18): Error: ignored value of `@mustuse` type `must_use.S`; prepend a `cast(void)` if intentional
 ---
 +/
 import core.attribute;
 
 @mustuse struct S {}
 
-S fun() { return S(); }
+S fun();
 
 void test()
 {
+    int x;
     fun();
+    fun(), x++;
 }