From 9c83d4c8efb64bce803e8e292b79dde86d53db2a Mon Sep 17 00:00:00 2001
From: 0-v-0 <kduice@qq.com>
Date: Sat, 27 Jun 2026 08:10:22 +0800
Subject: [PATCH] Fix #17749 - Ignore failing overload candidates

---
 compiler/src/dmd/templatesem.d       | 26 ++++++++++++++++++++++----
 compiler/test/compilable/test15801.d | 10 ++++++++++
 2 files changed, 32 insertions(+), 4 deletions(-)
 create mode 100644 compiler/test/compilable/test15801.d

diff --git a/compiler/src/dmd/templatesem.d b/compiler/src/dmd/templatesem.d
index 8221c2bed6fd..489eae089e52 100644
--- a/compiler/src/dmd/templatesem.d
+++ b/compiler/src/dmd/templatesem.d
@@ -3713,9 +3713,17 @@ bool findBestMatch(TemplateInstance ti, Scope* sc, ArgumentList argumentList)
         TemplateDeclaration td_best;
         TemplateDeclaration td_ambig;
         MATCH m_best = MATCH.nomatch;
+        uint candidateCount = 0;
 
         Dsymbol dstart = tovers ? tovers.a[oi] : ti.tempdecl;
         overloadApply(dstart, (Dsymbol s)
+        {
+            if (s.isTemplateDeclaration())
+                ++candidateCount;
+            return 0;
+        });
+        const gagCandidates = candidateCount > 1;
+        overloadApply(dstart, (Dsymbol s)
         {
             auto td = s.isTemplateDeclaration();
             if (!td)
@@ -3736,9 +3744,11 @@ bool findBestMatch(TemplateInstance ti, Scope* sc, ArgumentList argumentList)
             dedtypes.zero();
             assert(td.semanticRun != PASS.initial);
 
+            const olderrors = gagCandidates ? global.startGagging() : 0u;
             MATCH m = matchWithInstance(sc, td, ti, dedtypes, argumentList, 0);
+            const errors = gagCandidates && global.endGagging(olderrors);
             //printf("matchWithInstance = %d\n", m);
-            if (m == MATCH.nomatch) // no match at all
+            if (errors || m == MATCH.nomatch) // no match at all
                 return 0;
             if (m < m_best) goto Ltd_best;
             if (m > m_best) goto Ltd;
@@ -5511,9 +5521,17 @@ bool TemplateInstance_semanticTiargs(Loc loc, Scope* sc, Objects* tiargs, int fl
             }
             else
             {
-                sc = sc.startCTFE();
-                ea = ea.expressionSemantic(sc);
-                sc = sc.endCTFE();
+                const mightBeAlias = ea.op == EXP.variable || !definitelyValueParameter(ea);
+                if (mightBeAlias)
+                {
+                    ea = ea.expressionSemantic(sc);
+                }
+                else
+                {
+                    sc = sc.startCTFE();
+                    ea = ea.expressionSemantic(sc);
+                    sc = sc.endCTFE();
+                }
 
                 if (auto varExp = ea.isVarExp())
                 {
diff --git a/compiler/test/compilable/test15801.d b/compiler/test/compilable/test15801.d
new file mode 100644
index 000000000000..dc27024b153b
--- /dev/null
+++ b/compiler/test/compilable/test15801.d
@@ -0,0 +1,10 @@
+enum foo(alias sym) = 3;
+
+string str;
+
+static assert(foo!str == 3);
+
+enum bar(int n) = 2;
+enum bar(alias sym) = 3;
+
+static assert(bar!str == 3);