Port getSyntacticNullishnessSemantics changes

internal/checker/checker.go

@@ -12264,7 +12264,9 @@ func (c *Checker) getSyntacticNullishnessSemantics(node *ast.Node) PredicateSema
 	switch node.Kind {
 	case ast.KindAwaitExpression,
 		ast.KindCallExpression,
+		ast.KindTaggedTemplateExpression,
 		ast.KindElementAccessExpression,
+		ast.KindMetaProperty,
 		ast.KindNewExpression,
 		ast.KindPropertyAccessExpression,
 		ast.KindYieldExpression,
@@ -12282,6 +12284,8 @@ func (c *Checker) getSyntacticNullishnessSemantics(node *ast.Node) PredicateSema
 			ast.KindAmpersandAmpersandToken,
 			ast.KindAmpersandAmpersandEqualsToken:
 			return PredicateSemanticsSometimes
+		case ast.KindCommaToken:
+			return c.getSyntacticNullishnessSemantics(node.AsBinaryExpression().Right)
 		}
 		return PredicateSemanticsNever
 	case ast.KindConditionalExpression:

testdata/baselines/reference/submodule/compiler/predicateSemantics.errors.txt

@@ -9,17 +9,14 @@ predicateSemantics.ts(33,8): error TS2872: This kind of expression is always tru
 predicateSemantics.ts(34,11): error TS2872: This kind of expression is always truthy.
 predicateSemantics.ts(35,8): error TS2872: This kind of expression is always truthy.
 predicateSemantics.ts(36,8): error TS2872: This kind of expression is always truthy.
-predicateSemantics.ts(50,14): error TS2869: Right operand of ?? is unreachable because the left operand is never nullish.
 predicateSemantics.ts(51,14): error TS2869: Right operand of ?? is unreachable because the left operand is never nullish.
 predicateSemantics.ts(52,14): error TS2695: Left side of comma operator is unused and has no side effects.
 predicateSemantics.ts(52,14): error TS2869: Right operand of ?? is unreachable because the left operand is never nullish.
-predicateSemantics.ts(58,15): error TS2869: Right operand of ?? is unreachable because the left operand is never nullish.
-predicateSemantics.ts(68,1): error TS2869: Right operand of ?? is unreachable because the left operand is never nullish.
 predicateSemantics.ts(70,1): error TS2869: Right operand of ?? is unreachable because the left operand is never nullish.
 predicateSemantics.ts(71,1): error TS2869: Right operand of ?? is unreachable because the left operand is never nullish.
 
 
-==== predicateSemantics.ts (19 errors) ====
+==== predicateSemantics.ts (16 errors) ====
     declare let cond: any;
 
     // OK: One or other operand is possibly nullish
@@ -92,8 +89,6 @@ predicateSemantics.ts(71,1): error TS2869: Right operand of ?? is unreachable be
       const maybe = null as true | null;
       let i = 0;
       const d = (i++, maybe) ?? true; // ok
-                 ~~~~~~~~~~
-!!! error TS2869: Right operand of ?? is unreachable because the left operand is never nullish.
       const e = (i++, i++) ?? true; // error
                  ~~~~~~~~
 !!! error TS2869: Right operand of ?? is unreachable because the left operand is never nullish.
@@ -108,8 +103,6 @@ predicateSemantics.ts(71,1): error TS2869: Right operand of ?? is unreachable be
     class X {
       constructor() {
         const p = new.target ?? 32;
-                  ~~~~~~~~~~
-!!! error TS2869: Right operand of ?? is unreachable because the left operand is never nullish.
       }
     }
 
@@ -120,8 +113,6 @@ predicateSemantics.ts(71,1): error TS2869: Right operand of ?? is unreachable be
     ): T | null;
 
     tag`foo${1}` ?? 32; // ok
-    ~~~~~~~~~~~~
-!!! error TS2869: Right operand of ?? is unreachable because the left operand is never nullish.
 
     `foo${1}` ?? 32; // error
     ~~~~~~~~~