[SourceKit] Determine correctly whether typed variables in if/guard/while-let-statements have explicit type annotations

lib/AST/Decl.cpp

@@ -5806,11 +5806,24 @@ void VarDecl::setNamingPattern(NamedPattern *Pat) {
 }
 
 TypeRepr *VarDecl::getTypeReprOrParentPatternTypeRepr() const {
-  if (auto *param = dyn_cast<ParamDecl>(this))
-    return param->getTypeRepr();
-
-  if (auto *parentPattern = dyn_cast_or_null<TypedPattern>(getParentPattern()))
-    return parentPattern->getTypeRepr();
+  if (auto *Param = dyn_cast<ParamDecl>(this))
+    return Param->getTypeRepr();
+
+  auto *ParentPattern = getParentPattern();
+
+  if (auto *TyPattern = dyn_cast_or_null<TypedPattern>(ParentPattern))
+    return TyPattern->getTypeRepr();
+
+  // Handle typed if/guard/while-let as a special case (e.g. `if let x: Int
+  // = Optional.some(4)`), since the `TypedPattern` is not the top-level
+  // pattern here - instead it is an implicit `OptionalSomePattern`
+  if (auto *SomePattern =
+          dyn_cast_or_null<OptionalSomePattern>(ParentPattern)) {
+    if (auto *TyPattern =
+            dyn_cast<TypedPattern>(SomePattern->getSubPattern())) {
+      return TyPattern->getTypeRepr();
+    }
+  }
 
   return nullptr;
 }

test/SourceKit/VariableType/case.swift

@@ -0,0 +1,21 @@
+if case let x? = Optional.some(5) {}
+if case let y: Int? = Optional.some(5) {}
+guard case let z: String? = Optional.some("a") else { fatalError() }
+while case let w: String? = Optional.some("b") {}
+
+enum Pair<U, V> {
+  case pair(U, V)
+}
+
+switch Pair.pair(Optional.some(0), "test") {
+case .pair(let u, var v):
+  break
+}
+
+// RUN: %sourcekitd-test -req=collect-var-type %s -- %s | %FileCheck %s
+// CHECK: (1:13, 1:14): Int (explicit type: 0)
+// CHECK: (2:13, 2:14): Int? (explicit type: 1)
+// CHECK: (3:16, 3:17): String? (explicit type: 1)
+// CHECK: (4:16, 4:17): String? (explicit type: 1)
+// CHECK: (11:16, 11:17): Int? (explicit type: 0)
+// CHECK: (11:23, 11:24): String (explicit type: 0)

test/SourceKit/VariableType/if-let.swift

@@ -0,0 +1,17 @@
+guard var opt: Int = .some(23) else { fatalError() }
+
+func foo() {
+  guard let x = .some("abc") else { return }
+  guard let y: String = .some("def") else { return }
+
+  if let z: Int = .some(4) {}
+
+  while var w: Int = .some(5) {}
+}
+
+// RUN: %sourcekitd-test -req=collect-var-type %s -- %s | %FileCheck %s
+// CHECK: (1:11, 1:14): Int (explicit type: 1)
+// CHECK: (4:13, 4:14): String (explicit type: 0)
+// CHECK: (5:13, 5:14): String (explicit type: 1)
+// CHECK: (7:10, 7:11): Int (explicit type: 1)
+// CHECK: (9:13, 9:14): Int (explicit type: 1)