Add Forest support for creating try statements

Change-Id: Ib0241b929fa4c9eda533beec1e3f902973340821
Reviewed-on: https://dart-review.googlesource.com/55520
Reviewed-by: Dan Rubel <danrubel@google.com>
Commit-Queue: Brian Wilkerson <brianwilkerson@google.com>

pkg/analyzer/lib/src/fasta/ast_building_factory.dart

@@ -243,6 +243,16 @@ class AstBuildingForest
   Expression throwExpression(Token throwKeyword, Expression expression) =>
       astFactory.throwExpression(throwKeyword, expression);
 
+  @override
+  Statement tryStatement(
+          Token tryKeyword,
+          Statement body,
+          List<CatchClause> catchClauses,
+          Token finallyKeyword,
+          Statement finallyBlock) =>
+      astFactory.tryStatement(
+          tryKeyword, body, catchClauses, finallyKeyword, finallyBlock);
+
   @override
   Statement yieldStatement(Token yieldKeyword, Token star,
           Expression expression, Token semicolon) =>

pkg/front_end/lib/src/fasta/kernel/body_builder.dart

@@ -2384,19 +2384,11 @@ abstract class BodyBuilder<Expression, Statement, Arguments>
   @override
   void endTryStatement(int catchCount, Token tryKeyword, Token finallyKeyword) {
     Statement finallyBlock = popStatementIfNotNull(finallyKeyword);
-    List<Catch> catches = popList(catchCount);
+    Object catches = popList(catchCount);
     Statement tryBlock = popStatement();
-    kernel.Statement kernelFinallyBlock = toKernelStatement(finallyBlock);
-    kernel.Statement kernelTryBlock = toKernelStatement(tryBlock);
     if (compileTimeErrorInTry == null) {
-      if (catches != null) {
-        kernelTryBlock = new ShadowTryCatch(kernelTryBlock, catches);
-      }
-      if (kernelFinallyBlock != null) {
-        kernelTryBlock =
-            new ShadowTryFinally(kernelTryBlock, kernelFinallyBlock);
-      }
-      push(kernelTryBlock);
+      push(forest.tryStatement(
+          tryKeyword, tryBlock, catches, finallyKeyword, finallyBlock));
     } else {
       push(compileTimeErrorInTry);
       compileTimeErrorInTry = null;

pkg/front_end/lib/src/fasta/kernel/fangorn.dart

@@ -9,6 +9,7 @@ import 'dart:core' hide MapEntry;
 import 'package:kernel/ast.dart'
     show
         Arguments,
+        Catch,
         DartType,
         EmptyStatement,
         Expression,
@@ -53,6 +54,8 @@ import 'kernel_shadow_ast.dart'
         ShadowSyntheticExpression,
         ShadowThisExpression,
         ShadowThrow,
+        ShadowTryCatch,
+        ShadowTryFinally,
         ShadowTypeLiteral,
         ShadowYieldStatement;
 
@@ -274,6 +277,19 @@ class Fangorn extends Forest<Expression, Statement, Token, Arguments> {
       ..fileOffset = offsetForToken(throwKeyword);
   }
 
+  @override
+  Statement tryStatement(Token tryKeyword, Statement body,
+      List<Catch> catchClauses, Token finallyKeyword, Statement finallyBlock) {
+    Statement tryStatement = body;
+    if (catchClauses != null) {
+      tryStatement = new ShadowTryCatch(tryStatement, catchClauses);
+    }
+    if (finallyBlock != null) {
+      tryStatement = new ShadowTryFinally(tryStatement, finallyBlock);
+    }
+    return tryStatement;
+  }
+
   @override
   Statement yieldStatement(
       Token yieldKeyword, Token star, Expression expression, Token semicolon) {

pkg/front_end/lib/src/fasta/kernel/forest.dart

@@ -176,6 +176,17 @@ abstract class Forest<Expression, Statement, Location, Arguments> {
   /// [throwKeyword].
   Expression throwExpression(Location throwKeyword, Expression expression);
 
+  /// Return a representation of a try statement. The statement is introduced by
+  /// the [tryKeyword] and the given [body]. If catch clauses were included,
+  /// then the [catchClauses] will represent them, otherwise it will be `null`.
+  /// Similarly, if a finally block was included, then the [finallyKeyword] and
+  /// [finallyBlock] will be non-`null`, otherwise both will be `null`. If there
+  /// was an error in some part of the try statement, then an [errorReplacement]
+  /// might be provided, in which case it could be returned instead of the
+  /// representation of the try statement.
+  Statement tryStatement(Location tryKeyword, Statement body,
+      covariant catchClauses, Location finallyKeyword, Statement finallyBlock);
+
   /// Return a representation of a yield statement consisting of the
   /// [yieldKeyword], [star], [expression], and [semicolon]. The [star] is null
   /// when no star was included in the source code.

pkg/front_end/lib/src/fasta/kernel/kernel_ast_api.dart

@@ -105,8 +105,6 @@ export 'kernel_shadow_ast.dart'
         ShadowSuperPropertyGet,
         ShadowSwitchStatement,
         ShadowSyntheticExpression,
-        ShadowTryCatch,
-        ShadowTryFinally,
         ShadowVariableAssignment,
         ShadowVariableDeclaration,
         ShadowVariableGet,