fix: accept []string and []int in matrix refs (#2956)

Co-authored-by: no-hup <shauryaj.finance@gmail.com>

variables_test.go

@@ -43,3 +43,52 @@ func TestResolveMatrixRefsDoesNotMutateInput(t *testing.T) {
 	require.Nil(t, orig.Value, "input matrix was mutated: Ref rows must be resolved into a copy")
 	require.Equal(t, ".ARCH_VAR", orig.Ref, "input matrix Ref was altered")
 }
+
+// TestResolveMatrixRefsListTypes is a regression test for #2544. A `ref:` is
+// evaluated as a template expression, so it does not always resolve to a
+// []any: a list declared in a Taskfile does, but template functions such as
+// `keys` and `splitList` return a []string. Resolving a ref used to type
+// assert []any, so those references failed with "must resolve to a list" even
+// though the value was a list. The accepted types mirror the ones
+// itemsFromFor supports for `for: var:`.
+func TestResolveMatrixRefsListTypes(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name    string
+		value   any
+		want    []any
+		wantErr bool
+	}{
+		{name: "any slice", value: []any{"amd64", "arm64"}, want: []any{"amd64", "arm64"}},
+		{name: "string slice", value: []string{"amd64", "arm64"}, want: []any{"amd64", "arm64"}},
+		{name: "int slice", value: []int{1, 2}, want: []any{1, 2}},
+		{name: "string", value: "not a list", wantErr: true},
+		{name: "map", value: map[string]any{"key": "value"}, wantErr: true},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			t.Parallel()
+
+			matrix := ast.NewMatrix(
+				&ast.MatrixElement{Key: "ARCH", Value: &ast.MatrixRow{Ref: ".ARCH_VAR"}},
+			)
+
+			vars := ast.NewVars()
+			vars.Set("ARCH_VAR", ast.Var{Value: test.value})
+			cache := &templater.Cache{Vars: vars}
+
+			resolved, err := resolveMatrixRefs(matrix, cache)
+			if test.wantErr {
+				require.ErrorContains(t, err, `matrix reference ".ARCH_VAR" must resolve to a list`)
+				return
+			}
+			require.NoError(t, err)
+
+			row, ok := resolved.Get("ARCH")
+			require.True(t, ok, "ARCH row missing from resolved matrix")
+			require.Equal(t, test.want, row.Value)
+		})
+	}
+}