Fix crash when optional semicolon is used in a long single-line lambda

Summary:
Whenever a lambda:
1. Has a single statement
2. Can't be collapsed due to length
3. Uses an optional semicolon

It fails with:
```
com.google.googlejavaformat.FormattingError: 16:5: error: expected token: ';'; generated } instead
```

This fixes that by slightly reworking how statements are visited.

Reviewed By: hick209

Differential Revision: D32708821

fbshipit-source-id: d3f84dbfdea9e17c1e3919b4918e8f6c09cb6ade

core/src/main/java/com/facebook/ktfmt/KotlinInputAstVisitorBase.kt

@@ -392,6 +392,11 @@ open class KotlinInputAstVisitorBase(
     }
   }
 
+  private fun visitStatement(statement: PsiElement) {
+    builder.block(ZERO) { statement.accept(this) }
+    builder.guessToken(";")
+  }
+
   private fun visitStatements(statements: Array<PsiElement>) {
     var first = true
     builder.guessToken(";")
@@ -401,8 +406,7 @@ open class KotlinInputAstVisitorBase(
         builder.blankLineWanted(OpsBuilder.BlankLineWanted.PRESERVE)
       }
       first = false
-      builder.block(ZERO) { statement.accept(this) }
-      builder.guessToken(";")
+      visitStatement(statement)
     }
   }
 
@@ -831,7 +835,7 @@ open class KotlinInputAstVisitorBase(
         if (statements.size == 1 &&
             statements.first() !is KtReturnExpression &&
             lambdaExpression.bodyExpression?.startsWithComment() != true) {
-          statements[0].accept(this)
+          visitStatement(statements[0])
         } else {
           visitStatements(statements)
         }

core/src/test/java/com/facebook/ktfmt/FormatterKtTest.kt

@@ -3073,6 +3073,9 @@ class FormatterKtTest {
       |  when {
       |    true -> "1"; false -> "0"
       |  }
+      |  someLongVariableName.let {
+      |    someReallyLongFunctionNameThatMakesThisNotFitInOneLineWithTheAboveVariable();
+      |  }
       |} ;
       |
       |""".trimMargin()
@@ -3097,6 +3100,9 @@ class FormatterKtTest {
       |    true -> "1"
       |    false -> "0"
       |  }
+      |  someLongVariableName.let {
+      |    someReallyLongFunctionNameThatMakesThisNotFitInOneLineWithTheAboveVariable()
+      |  }
       |}
       |""".trimMargin()
     assertThatFormatting(code).isEqualTo(expected)