Address PR feedback

Author: stephentoub

src/libraries/System.Text.RegularExpressions/gen/RegexGenerator.Emitter.cs

@@ -783,7 +783,7 @@ string ReserveName(string prefix)
 
             // Emit failure
             writer.WriteLine("// No match");
-            MarkLabel(originalDoneLabel);
+            MarkLabel(originalDoneLabel, emitSemicolon: !expressionHasCaptures);
             if (expressionHasCaptures)
             {
                 EmitUncaptureUntil("0");
@@ -1156,7 +1156,7 @@ void EmitExpressionConditional(RegexNode node)
 
                     // Emit the no branch, first uncapturing any captures from the expression condition that failed
                     // to match and emit the branch.
-                    MarkLabel(no);
+                    MarkLabel(no, emitSemicolon: startingCrawlPos is null);
                     if (startingCrawlPos is not null)
                     {
                         EmitUncaptureUntil(startingCrawlPos);
@@ -1252,7 +1252,7 @@ void EmitNegativeLookaheadAssertion(RegexNode node)
                 writer.WriteLine($"goto {originalDoneLabel};");
 
                 // Failures (success for a negative lookahead) jump here.
-                MarkLabel(negativeLookaheadDoneLabel);
+                MarkLabel(negativeLookaheadDoneLabel, emitSemicolon: false);
                 Debug.Assert(doneLabel == negativeLookaheadDoneLabel);
                 doneLabel = originalDoneLabel;
 

src/libraries/System.Text.RegularExpressions/tests/Regex.KnownPattern.Tests.cs

@@ -1159,14 +1159,14 @@ public async Task Blog_Levithan_BalancingGroups_MatchingParentheses(RegexEngine
             }
 
             Regex r = await RegexHelpers.GetRegexAsync(engine, @"^\(
-	                                                                 (?>
-		                                                                 [^()]+
-	                                                                 |
-		                                                                 \( (?<Depth>)
-	                                                                 |
-		                                                                 \) (?<-Depth>)
-	                                                                 )*
-	                                                                 (?(Depth)(?!))
+                                                                     (?>
+                                                                         [^()]+
+                                                                     |
+                                                                         \( (?<Depth>)
+                                                                     |
+                                                                         \) (?<-Depth>)
+                                                                     )*
+                                                                     (?(Depth)(?!))
                                                                  \)$", RegexOptions.IgnorePatternWhitespace);
 
             Assert.True(r.IsMatch("()"));
@@ -1190,15 +1190,15 @@ public async Task Blog_Levithan_BalancingGroups_WordLengthIncreases(RegexEngine
             }
 
             Regex r = await RegexHelpers.GetRegexAsync(engine, @"^(?:
-	                                                                 (?(A)\s|)
-	                                                                 (?<B>)
-	                                                                 (?<C-B>\w)+ (?(B)(?!))
-	                                                                 (?:
-		                                                                 \s
-		                                                                 (?<C>)
-		                                                                 (?<B-C>\w)+ (?(C)(?!))
-		                                                                 (?<A>)
-	                                                                 )?
+                                                                     (?(A)\s|)
+                                                                     (?<B>)
+                                                                     (?<C-B>\w)+ (?(B)(?!))
+                                                                     (?:
+                                                                         \s
+                                                                         (?<C>)
+                                                                         (?<B-C>\w)+ (?(C)(?!))
+                                                                         (?<A>)
+                                                                     )?
                                                                  )+ \b$", RegexOptions.IgnorePatternWhitespace);
 
             Assert.True(r.IsMatch("a bc def ghij klmni"));