Add VariableType test cases for if/guard/while-let

- Add VariableType test case for guarded variables
- Add if-let to VariableType test case
- Add while-let test case for VariableType
- Test pattern matching with VariableType
- Test guard/while-case-let with VariableType

Author: fwcd

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)