Fix baseof block regression

From Hugo 0.74.0.

Fixes #7478

hugolib/hugo_sites_build_errors_test.go

@@ -65,7 +65,8 @@ func TestSiteBuildErrors(t *testing.T) {
 			fileFixer: func(content string) string {
 				return strings.Replace(content, ".Title }}", ".Title }", 1)
 			},
-			assertCreateError: func(a testSiteBuildErrorAsserter, err error) {
+			// Base templates gets parsed at build time.
+			assertBuildError: func(a testSiteBuildErrorAsserter, err error) {
 				a.assertLineNumber(4, err)
 			},
 		},
@@ -90,7 +91,7 @@ func TestSiteBuildErrors(t *testing.T) {
 				a.c.Assert(fe.Position().LineNumber, qt.Equals, 5)
 				a.c.Assert(fe.Position().ColumnNumber, qt.Equals, 1)
 				a.c.Assert(fe.ChromaLexer, qt.Equals, "go-html-template")
-				a.assertErrorMessage("\"layouts/_default/single.html:5:1\": parse failed: template: _default/single.html.___b:5: unexpected \"}\" in operand", fe.Error())
+				a.assertErrorMessage("\"layouts/foo/single.html:5:1\": parse failed: template: foo/single.html:5: unexpected \"}\" in operand", fe.Error())
 
 			},
 		},

hugolib/template_test.go

@@ -677,3 +677,46 @@ P3: Inline: p3
 	)
 
 }
+
+// https://github.com/gohugoio/hugo/issues/7478
+func TestBaseWithAndWithoutDefine(t *testing.T) {
+
+	b := newTestSitesBuilder(t)
+
+	b.WithContent("p1.md", "---\ntitle: P\n---\nContent")
+
+	b.WithTemplates(
+		"_default/baseof.html", `
+::Header Start:{{ block "header" . }}{{ end }}:Header End:
+::{{ block "main" . }}Main{{ end }}::
+`, "index.html", `
+{{ define "header" }}
+Home Header
+{{ end }}
+{{ define "main" }}
+This is home main
+{{ end }}
+`,
+
+		"_default/single.html", `
+{{ define "main" }}
+This is single main
+{{ end }}
+`,
+	)
+
+	b.CreateSites().Build(BuildCfg{})
+
+	b.AssertFileContent("public/index.html", `
+Home Header
+This is home main
+`,
+	)
+
+	b.AssertFileContent("public/p1/index.html", `
+ ::Header Start::Header End:
+This is single main
+`,
+	)
+
+}