From ff02184b2e0beebeb5d0bbc3ce86bf78e583d28f Mon Sep 17 00:00:00 2001
From: gingerBill <gingerBill@users.noreply.github.com>
Date: Fri, 2 Oct 2026 16:42:33 +0100
Subject: [PATCH] Fix #7708: compare a polymorphic record's constant parameters
 by value in `subst_unify`

---
 src/check_type.cpp   | 5 +++++
 tests/issues/run.bat | 2 ++
 tests/issues/run.sh  | 7 +++++++
 3 files changed, 14 insertions(+)

diff --git a/src/check_type.cpp b/src/check_type.cpp
index d04fbfe8e..8555140cc 100644
--- a/src/check_type.cpp
+++ b/src/check_type.cpp
@@ -2127,6 +2127,11 @@ gb_internal SubstResult subst_unify(CheckerContext *c, Type *pattern, Type *sour
 				if (r != Subst_Matched) {
 					return r; // NoMatch or Unhandled
 				}
+				// e.g. `M(1, 1, $T)` vs `M(3, 3, f64)`
+				if (s_e->kind == Entity_Constant && t_e->kind == Entity_Constant &&
+				    !compare_exact_values(Token_CmpEq, s_e->Constant.value, t_e->Constant.value)) {
+					return Subst_NoMatch;
+				}
 			}
 		}
 		return Subst_Matched;
diff --git a/tests/issues/run.bat b/tests/issues/run.bat
index 2c2004955..1c68c582d 100644
--- a/tests/issues/run.bat
+++ b/tests/issues/run.bat
@@ -84,6 +84,8 @@ clang -c ..\test_issue_sysv_abi.c -o test_issue_sysv_abi_c.o || exit /b
 ..\..\..\odin test ..\test_issue_7316.odin %COMMON%  || exit /b
 ..\..\..\odin test ..\test_issue_7566.odin %COMMON%  || exit /b
 ..\..\..\odin test ..\test_issue_poly_using_subtype.odin %COMMON%  || exit /b
+..\..\..\odin test ..\test_issue_7708.odin %COMMON%  || exit /b
+..\..\..\odin check ..\test_issue_7708_mismatch.odin %COMMON% 2>&1 | find /c "Error:" | findstr /x "2" || exit /b
 ..\..\..\odin test ..\test_issue_7587.odin %COMMON%  || exit /b
 ..\..\..\odin run ..\test_issue_7596.odin %COMMON% || exit /b
 
diff --git a/tests/issues/run.sh b/tests/issues/run.sh
index fb50f87cd..e8912b635 100755
--- a/tests/issues/run.sh
+++ b/tests/issues/run.sh
@@ -105,6 +105,13 @@ $ODIN run ../test_issue_7564.odin $COMMON
 $ODIN test ../test_issue_7316.odin $COMMON
 $ODIN test ../test_issue_7566.odin $COMMON
 $ODIN test ../test_issue_poly_using_subtype.odin $COMMON
+$ODIN test ../test_issue_7708.odin $COMMON
+if [[ $($ODIN check ../test_issue_7708_mismatch.odin $COMMON_CHECK 2>&1 >/dev/null | grep -c "Error:") -eq 2 ]]; then
+	echo "SUCCESSFUL 1/1"
+else
+	echo "SUCCESSFUL 0/1"
+	exit 1
+fi
 $ODIN test ../test_issue_7587.odin $COMMON
 $ODIN run ../test_issue_7596.odin $COMMON
 $ODIN test ../test_issue_7421.odin $COMMON