Port optional catch clause variable declaration transform (#1273)

Author: weswigham

internal/ast/ast.go

@@ -2927,8 +2927,12 @@ func (node *CatchClause) Clone(f NodeFactoryCoercible) *Node {
 }
 
 func (node *CatchClause) computeSubtreeFacts() SubtreeFacts {
-	return propagateSubtreeFacts(node.VariableDeclaration) |
+	res := propagateSubtreeFacts(node.VariableDeclaration) |
 		propagateSubtreeFacts(node.Block)
+	if node.VariableDeclaration == nil {
+		res |= SubtreeContainsES2019
+	}
+	return res
 }
 
 func (node *CatchClause) propagateSubtreeFacts() SubtreeFacts {

internal/transformers/estransforms/optionalcatch.go

@@ -11,7 +11,25 @@ type optionalCatchTransformer struct {
 }
 
 func (ch *optionalCatchTransformer) visit(node *ast.Node) *ast.Node {
-	return node // !!!
+	if node.SubtreeFacts()&ast.SubtreeContainsES2019 == 0 {
+		return node
+	}
+	switch node.Kind {
+	case ast.KindCatchClause:
+		return ch.visitCatchClause(node.AsCatchClause())
+	default:
+		return ch.Visitor().VisitEachChild(node)
+	}
+}
+
+func (ch *optionalCatchTransformer) visitCatchClause(node *ast.CatchClause) *ast.Node {
+	if node.VariableDeclaration == nil {
+		return ch.Factory().NewCatchClause(
+			ch.Factory().NewVariableDeclaration(ch.Factory().NewTempVariable(), nil, nil, nil),
+			ch.Visitor().Visit(node.Block),
+		)
+	}
+	return ch.Visitor().VisitEachChild(node.AsNode())
 }
 
 func newOptionalCatchTransformer(emitContext *printer.EmitContext) *transformers.Transformer {

testdata/baselines/reference/submodule/compiler/constructorWithIncompleteTypeAnnotation.js

@@ -424,7 +424,7 @@ class BasicFeatures {
         var xx = c;
         retVal += ;
         try { }
-        catch { }
+        catch (_a) { }
         Property;
         retVal += c.Member();
         retVal += xx.Foo() ? 0 : 1;

testdata/baselines/reference/submodule/compiler/constructorWithIncompleteTypeAnnotation.js.diff

@@ -30,16 +30,7 @@
          if(retValue) { }
      }
      TypeScriptAllInOne.Program = Program;
-@@= skipped -130, +131 lines =@@
-         var xx = c;
-         retVal += ;
-         try { }
--        catch (_a) { }
-+        catch { }
-         Property;
-         retVal += c.Member();
-         retVal += xx.Foo() ? 0 : 1;
-@@= skipped -48, +48 lines =@@
+@@= skipped -178, +179 lines =@@
      }
  }
  class CLASS {

testdata/baselines/reference/submodule/compiler/controlFlowDestructuringVariablesInTryCatch.js

@@ -31,7 +31,7 @@ try {
     var [d = 1] = [];
     var { e = 1 } = {};
 }
-catch {
+catch (_a) {
     console.error("error");
 }
 a;

testdata/baselines/reference/submodule/compiler/controlFlowDestructuringVariablesInTryCatch.js.diff

@@ -7,13 +7,4 @@
 -"use strict";
  try {
      var a = f1();
-     var [b] = f2();
-@@= skipped -8, +7 lines =@@
-     var [d = 1] = [];
-     var { e = 1 } = {};
- }
--catch (_a) {
-+catch {
-     console.error("error");
- }
- a;
+     var [b] = f2();

testdata/baselines/reference/submodule/compiler/potentiallyUnassignedVariableInCatch.js

@@ -18,6 +18,6 @@ try {
         foo = 1234;
     }
 }
-catch {
+catch (_a) {
     foo;
 }

testdata/baselines/reference/submodule/compiler/potentiallyUnassignedVariableInCatch.js.diff

@@ -7,11 +7,4 @@
 -"use strict";
  let foo;
  try {
-     if (Math.random() > 0.5) {
-         foo = 1234;
-     }
- }
--catch (_a) {
-+catch {
-     foo;
- }
+     if (Math.random() > 0.5) {

testdata/baselines/reference/submodule/compiler/tryCatchFinallyControlFlow.js

@@ -551,7 +551,7 @@ const main = () => {
         hoge = 'hoge!';
         return;
     }
-    catch {
+    catch (_a) {
         return;
     }
     finally {

testdata/baselines/reference/submodule/compiler/tryCatchFinallyControlFlow.js.diff

@@ -7,13 +7,4 @@
 -"use strict";
  // Repro from #34797
  function f1() {
-     let a = null;
-@@= skipped -220, +219 lines =@@
-         hoge = 'hoge!';
-         return;
-     }
--    catch (_a) {
-+    catch {
-         return;
-     }
-     finally {
+     let a = null;