[patch] Accept only one declared SectionType name in a section header

Semantics.Music/Section.cs

@@ -126,7 +126,7 @@
 			return false;
 		}
 
-		if (!Enum.TryParse<SectionType>(header[1..close], out SectionType type))
+		if (!TryParseSectionType(header[1..close], out SectionType type))
 		{
 			return false;
 		}
@@ -163,4 +163,25 @@
 		result = Create(type, progression, label, key);
 		return true;
 	}
+
+	// Enum.TryParse alone also takes integers, comma-separated name lists and padded names, all of
+	// which ToString never writes. Only the exact name of one declared member is a section type.
+	private static bool TryParseSectionType(string name, out SectionType type)
+	{
+		type = default;
+		if (name.Length == 0)
+		{
+			return false;
+		}
+
+		foreach (char c in name)
+		{
+			if (c is not ((>= 'A' and <= 'Z') or (>= 'a' and <= 'z')))
+			{
+				return false;
+			}
+		}
+
+		return Enum.TryParse(name, out type) && Enum.IsDefined(type);
+	}
 }

Semantics.Test/Music/SectionRoundTripTests.cs

@@ -30,4 +30,26 @@ public void RoundTripWithLabelAndKey()
 		Section s = Section.Create(SectionType.Chorus, SampleProgression(), "Chorus", Key.Create(PitchClass.Create(NoteLetter.A, Accidental.Natural), Mode.Aeolian));
 		Assert.AreEqual(s, Section.Parse(s.ToString()));
 	}
+
+	[TestMethod]
+	[DataRow("[Verse, Chorus]\n4/4  Dm7 / G7 /")]
+	[DataRow("[42]\n4/4  Dm7 / G7 /")]
+	[DataRow("[-1]\n4/4  Dm7 / G7 /")]
+	[DataRow("[ Verse ]\n4/4  Dm7 / G7 /")]
+	[DataRow("[verse]\n4/4  Dm7 / G7 /")]
+	public void TryParseRejectsHeaderThatIsNotOneSectionTypeName(string text)
+	{
+		Assert.IsFalse(Section.TryParse(text, out Section? result));
+		Assert.IsNull(result);
+	}
+
+	[TestMethod]
+	public void TryParseAcceptsEverySectionTypeName()
+	{
+		foreach (SectionType type in Enum.GetValues<SectionType>())
+		{
+			Section s = Section.Create(type, SampleProgression());
+			Assert.AreEqual(s, Section.Parse(s.ToString()));
+		}
+	}
 }