[CodeCompletion] Handle ExprPattern in context type analysis

This improves type inference for code completion in argument position of
EnumElementPattern.

Author: rintaro

lib/IDE/CodeCompletion.cpp

@@ -4974,6 +4974,18 @@ namespace  {
         Ancestors.pop_back();
       return true;
     }
+
+    std::pair<bool, Pattern *> walkToPatternPre(Pattern *P) override {
+      if (Predicate(P))
+        Ancestors.push_back(P);
+      return { true, P };
+    }
+
+    Pattern *walkToPatternPost(Pattern *P) override {
+      if (Predicate(P))
+        Ancestors.pop_back();
+      return P;
+    }
   };
 } // end anonymous namespace
 
@@ -5020,6 +5032,13 @@ class CodeCompletionTypeContextAnalyzer {
         default:
           return false;
         }
+      } else if (auto P = Node.getAsPattern()) {
+        switch (P->getKind()) {
+        case PatternKind::Expr:
+          return true;
+        default:
+          return false;
+        }
       } else
         return false;
     }) {}
@@ -5060,7 +5079,7 @@ class CodeCompletionTypeContextAnalyzer {
         break;
       }
       default:
-        llvm_unreachable("Unhandled expression kinds.");
+        llvm_unreachable("Unhandled expression kind.");
     }
   }
 
@@ -5085,7 +5104,7 @@ class CodeCompletionTypeContextAnalyzer {
       }
       break;
     default:
-      llvm_unreachable("Unhandled statement kinds.");
+      llvm_unreachable("Unhandled statement kind.");
     }
   }
 
@@ -5127,7 +5146,22 @@ class CodeCompletionTypeContextAnalyzer {
         break;
       }
       default:
-        llvm_unreachable("Unhandled decl kinds.");
+        llvm_unreachable("Unhandled decl kind.");
+    }
+  }
+
+  void analyzePattern(Pattern *P, llvm::function_ref<void(Type)> Callback) {
+    switch (P->getKind()) {
+    case PatternKind::Expr: {
+      auto ExprPat = cast<ExprPattern>(P);
+      if (auto D = ExprPat->getMatchVar()) {
+        if (D->hasInterfaceType())
+          Callback(D->getInterfaceType());
+      }
+      break;
+    }
+    default:
+      llvm_unreachable("Unhandled pattern kind.");
     }
   }
 
@@ -5155,6 +5189,8 @@ class CodeCompletionTypeContextAnalyzer {
         analyzeStmt(Parent, Callback);
       } else if (auto Parent = It->getAsDecl()) {
         analyzeDecl(Parent, Callback);
+      } else if (auto Parent = It->getAsPattern()) {
+        analyzePattern(Parent, Callback);
       }
       if (!PossibleTypes.empty() || !PossibleNames.empty())
         return true;

lib/Parse/ParsePattern.cpp

@@ -1109,10 +1109,9 @@ ParserResult<Pattern> Parser::parseMatchingPattern(bool isExprBasic) {
   // disambiguate.
   ParserResult<Expr> subExpr =
     parseExprImpl(diag::expected_pattern, isExprBasic);
-  if (subExpr.hasCodeCompletion())
-    return makeParserCodeCompletionStatus();
+  ParserStatus status = subExpr;
   if (subExpr.isNull())
-    return nullptr;
+    return status;
 
   if (SyntaxContext->isEnabled()) {
     if (auto UPES = PatternCtx.popIf<UnresolvedPatternExprSyntax>()) {
@@ -1125,9 +1124,9 @@ ParserResult<Pattern> Parser::parseMatchingPattern(bool isExprBasic) {
   // obvious pattern, which will come back wrapped in an immediate
   // UnresolvedPatternExpr.  Transform this now to simplify later code.
   if (auto *UPE = dyn_cast<UnresolvedPatternExpr>(subExpr.get()))
-    return makeParserResult(UPE->getSubPattern());
+    return makeParserResult(status, UPE->getSubPattern());
 
-  return makeParserResult(new (Context) ExprPattern(subExpr.get()));
+  return makeParserResult(status, new (Context) ExprPattern(subExpr.get()));
 }
 
 ParserResult<Pattern> Parser::parseMatchingPatternAsLetOrVar(bool isLet,

test/IDE/complete_enum_elements.swift

@@ -28,7 +28,7 @@
 // RUN: %FileCheck %s -check-prefix=FOO_ENUM_DOT < %t.enum.txt
 
 // RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=ENUM_SW_IN_PATTERN_1 > %t.enum.txt
-// RUN: %FileCheck %s -check-prefix=WITH_GLOBAL_RESULTS < %t.enum.txt
+// RUN: %FileCheck %s -check-prefix=WITH_GLOBAL_RESULTS_INVALID < %t.enum.txt
 // RUN: %FileCheck %s -check-prefix=ENUM_SW_IN_PATTERN_1 < %t.enum.txt
 
 // RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=ENUM_SW_IN_PATTERN_2 > %t.enum.txt
@@ -280,6 +280,10 @@ func freeFunc() {}
 // WITH_GLOBAL_RESULTS: Decl[FreeFunction]/CurrModule: freeFunc()[#Void#]{{; name=.+$}}
 // WITH_GLOBAL_RESULTS: End completions
 
+// WITH_GLOBAL_RESULTS_INVALID: Begin completions
+// WITH_GLOBAL_RESULTS_INVALID: Decl[FreeFunction]/CurrModule/NotRecommended/TypeRelation[Invalid]: freeFunc()[#Void#]{{; name=.+$}}
+// WITH_GLOBAL_RESULTS_INVALID: End completions
+
 //===--- Complete enum elements in 'switch'.
 
 func testSwitch1(e: FooEnum) {

test/IDE/complete_pattern.swift

@@ -55,6 +55,8 @@
 // RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=MULTI_PATTERN_3 | %FileCheck %s -check-prefix=MULTI_PATTERN_3
 // RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=MULTI_PATTERN_4 | %FileCheck %s -check-prefix=MULTI_PATTERN_4
 
+// RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=CC_IN_PATTERN_1 | %FileCheck %s -check-prefix=CC_IN_PATTERN_1
+
 
 //===--- Helper types that are used in this test
 
@@ -261,3 +263,19 @@ func test_multiple_patterns4(x: Int) {
 // MULTI_PATTERN_4-DAG: Decl[LocalVar]/Local: x[#Int#]{{; name=.+$}}
 // MULTI_PATTERN_4: End completions
 
+enum IntHolder {
+  case hold(Int)
+}
+func ident(int: Int) -> Int { return int }
+func ident(double: Double) -> Int { return Double }
+
+func test_cc_in_pattern(subject: IntHolder, i1: Int) {
+  switch subject {
+  case .hold(#^CC_IN_PATTERN_1^#):
+    ()
+  }
+}
+
+// CC_IN_PATTERN_1: Begin completions
+// CC_IN_PATTERN_1-DAG: Decl[LocalVar]/Local/TypeRelation[Identical]: i1[#Int#]; name=i1
+// CC_IN_PATTERN_1: End completions