[code-completion] Fix correctness regressions from disabling diagnostics in code completion

There were some changes to completion results because AST mutations that were
made while diagnosing are no longer happening.

This patch 1) changes expression type checking to allow unresolved types when
solving constraint systems, so we get a solution and apply its types in more
cases, and 2) fixes a parsing issue where we would drop a ternary expression
completely if the code completion point was in its true branch.

Author: Nathan Hawes

lib/IDE/ExprContextAnalysis.cpp

@@ -384,6 +384,11 @@ static bool collectPossibleCalleesForApply(
   } else if (auto *UDE = dyn_cast<UnresolvedDotExpr>(fnExpr)) {
     collectPossibleCalleesByQualifiedLookup(
         DC, UDE->getBase(), UDE->getName().getBaseName(), candidates);
+  } else if (auto *DSCE = dyn_cast<DotSyntaxCallExpr>(fnExpr)) {
+    if (auto *DRE = dyn_cast<DeclRefExpr>(DSCE->getFn())) {
+    collectPossibleCalleesByQualifiedLookup(
+        DC, DSCE->getArg(), DRE->getDecl()->getBaseName(), candidates);
+    }
   }
 
   if (candidates.empty()) {

lib/Parse/ParseExpr.cpp

@@ -236,17 +236,19 @@ ParserResult<Expr> Parser::parseExprSequence(Diag<> Message,
       // Parse the middle expression of the ternary.
       ParserResult<Expr> middle =
           parseExprSequence(diag::expected_expr_after_if_question, isExprBasic);
+      ParserStatus Status = middle;
       if (middle.hasCodeCompletion())
-        return makeParserCodeCompletionResult<Expr>();
+        HasCodeCompletion = true;
       if (middle.isNull())
         return nullptr;
 
       // Make sure there's a matching ':' after the middle expr.
       if (!Tok.is(tok::colon)) {
         diagnose(questionLoc, diag::expected_colon_after_if_question);
 
-        return makeParserErrorResult(new (Context) ErrorExpr(
-            {startLoc, middle.get()->getSourceRange().End}));
+      Status.setIsParseError();
+      return makeParserResult(Status, new (Context) ErrorExpr(
+          {startLoc, middle.get()->getSourceRange().End}));
       }
 
       SourceLoc colonLoc = consumeToken();

lib/Sema/TypeCheckStmt.cpp

@@ -519,20 +519,18 @@ class StmtChecker : public StmtVisitor<StmtChecker, Stmt*> {
       }
     }
 
+    if (EndTypeCheckLoc.isValid()) {
+      assert(DiagnosticSuppression::isEnabled(TC.Diags) &&
+             "Diagnosing and AllowUnresolvedTypeVariables don't seem to mix");
+      options |= TypeCheckExprFlags::AllowUnresolvedTypeVariables;
+    }
+
     ContextualTypePurpose ctp = CTP_ReturnStmt;
     if (auto func =
             dyn_cast_or_null<FuncDecl>(TheFunc->getAbstractFunctionDecl())) {
       if (func->hasSingleExpressionBody()) {
         ctp = CTP_ReturnSingleExpr;
       }
-
-      // If we are performing code-completion inside a function builder body,
-      // suppress diagnostics to workaround typechecking performance problems.
-      if (func->getFunctionBuilderType() &&
-          TC.Context.SourceMgr.rangeContainsCodeCompletionLoc(
-              func->getBody()->getSourceRange())) {
-        options |= TypeCheckExprFlags::SuppressDiagnostics;
-      }
     }
 
     auto exprTy = TC.typeCheckExpression(E, DC, TypeLoc::withoutLoc(ResultTy),
@@ -1786,6 +1784,12 @@ Stmt *StmtChecker::visitBraceStmt(BraceStmt *BS) {
       if (isDiscarded)
         options |= TypeCheckExprFlags::IsDiscarded;
 
+      if (EndTypeCheckLoc.isValid()) {
+        assert(DiagnosticSuppression::isEnabled(TC.Diags) &&
+               "Diagnosing and AllowUnresolvedTypeVariables don't seem to mix");
+        options |= TypeCheckExprFlags::AllowUnresolvedTypeVariables;
+      }
+
       auto resultTy =
           TC.typeCheckExpression(SubExpr, DC, TypeLoc(), CTP_Unused, options);
 

test/IDE/complete_in_closures.swift

@@ -57,6 +57,9 @@
 // RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=IN_IIFE_4 | %FileCheck %s -check-prefix=IN_IIFE_1
 // RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=ERROR_IN_CLOSURE_IN_INITIALIZER | %FileCheck %s -check-prefix=ERROR_IN_CLOSURE_IN_INITIALIZER
 // RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=DECL_IN_CLOSURE_IN_TOPLEVEL_INIT | %FileCheck %s -check-prefix=DECL_IN_CLOSURE_IN_TOPLEVEL_INIT
+// RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=SINGLE_EXPR_CLOSURE_CONTEXT | %FileCheck %s -check-prefix=SINGLE_EXPR_CLOSURE_CONTEXT
+// RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=SINGLE_TERNARY_EXPR_CLOSURE_CONTEXT | %FileCheck %s -check-prefix=SINGLE_TERNARY_EXPR_CLOSURE_CONTEXT
+
 
 // ERROR_COMMON: found code completion token
 // ERROR_COMMON-NOT: Begin completions
@@ -401,3 +404,30 @@ var foo = {
   // DECL_IN_CLOSURE_IN_TOPLEVEL_INIT-DAG: Decl[InstanceMethod]/Super:         dropFirst()[#Substring#]; name=dropFirst()
   // DECL_IN_CLOSURE_IN_TOPLEVEL_INIT: End completions
 }
+
+func testWithMemoryRebound(_ bar: UnsafePointer<UInt64>) {
+    _ = bar.withMemoryRebound(to: Int64.self, capacity: 3) { ptr in
+        return ptr #^SINGLE_EXPR_CLOSURE_CONTEXT^#
+        // SINGLE_EXPR_CLOSURE_CONTEXT: Begin completions
+        // SINGLE_EXPR_CLOSURE_CONTEXT-DAG: Decl[InstanceMethod]/CurrNominal:   .deallocate()[#Void#]; name=deallocate()
+        // SINGLE_EXPR_CLOSURE_CONTEXT-DAG: Decl[InstanceVar]/CurrNominal:      .pointee[#Int64#]; name=pointee
+        // SINGLE_EXPR_CLOSURE_CONTEXT: End completions
+    }
+}
+
+func testInsideTernaryClosureReturn(test: Bool) -> [String] {
+    return "hello".map { thing in
+        test ? String(thing #^SINGLE_TERNARY_EXPR_CLOSURE_CONTEXT^#).uppercased() : String(thing).lowercased()
+        // SINGLE_TERNARY_EXPR_CLOSURE_CONTEXT: Begin completions
+        // SINGLE_TERNARY_EXPR_CLOSURE_CONTEXT-DAG: Decl[InstanceVar]/CurrNominal:      .utf8[#Character.UTF8View#]; name=utf8
+        // SINGLE_TERNARY_EXPR_CLOSURE_CONTEXT-DAG: Decl[InstanceVar]/CurrNominal:      .description[#String#]; name=description
+        // SINGLE_TERNARY_EXPR_CLOSURE_CONTEXT-DAG: Decl[InstanceVar]/CurrNominal:      .isWhitespace[#Bool#]; name=isWhitespace
+        // SINGLE_TERNARY_EXPR_CLOSURE_CONTEXT-DAG: Decl[InstanceMethod]/CurrNominal:   .uppercased()[#String#]; name=uppercased()
+        // SINGLE_TERNARY_EXPR_CLOSURE_CONTEXT-DAG: Decl[InfixOperatorFunction]/OtherModule[Swift]: [' ']... {#String.Element#}[#ClosedRange<String.Element>#]; name=... String.Element
+        // SINGLE_TERNARY_EXPR_CLOSURE_CONTEXT-DAG: Decl[InfixOperatorFunction]/OtherModule[Swift]: [' ']< {#Character#}[#Bool#]; name=< Character
+        // SINGLE_TERNARY_EXPR_CLOSURE_CONTEXT-DAG: Decl[InfixOperatorFunction]/OtherModule[Swift]: [' ']>= {#String.Element#}[#Bool#]; name=>= String.Element
+        // SINGLE_TERNARY_EXPR_CLOSURE_CONTEXT-DAG: Decl[InfixOperatorFunction]/OtherModule[Swift]: [' ']== {#Character#}[#Bool#]; name=== Character
+        // SINGLE_TERNARY_EXPR_CLOSURE_CONTEXT-DAG: Keyword[self]/CurrNominal:          .self[#String.Element#]; name=self
+        // SINGLE_TERNARY_EXPR_CLOSURE_CONTEXT: End completions
+    }
+}

test/SourceKit/CodeComplete/injected_vfs_complete_open.swift

@@ -42,7 +42,6 @@ func foo(
 // RUN:   == -req=complete.update -pos=9:1 -req-opts=filtertext=StructDefinedInSameTarget %s | %FileCheck --check-prefix=INNER_SAMETARGET %s
 // INNER_SAMETARGET: key.name: "StructDefinedInSameTarget"
 // INNER_SAMETARGET: key.name: "StructDefinedInSameTarget."
-// INNER_SAMETARGET: key.name: "StructDefinedInSameTarget("
 
 // RUN: %sourcekitd-test -req=complete.open -pos=9:1 -req-opts=filtertext=StructDefinedInCModule -vfs-files=/target_file2.swift=@%S/../Inputs/vfs/other_file_in_target.swift,/CModule/module.modulemap=%S/../Inputs/vfs/CModule/module.modulemap,/CModule/CModule.h=%S/../Inputs/vfs/CModule/CModule.h,/SwiftModule/SwiftModule.swiftmodule=%t/SwiftModule.swiftmodule %s -pass-as-sourcetext -- %s /target_file2.swift -I /CModule -I /SwiftModule -target %target-triple | %FileCheck --check-prefix=INNER_CMODULE %s
 // RUN: %sourcekitd-test -req=complete.open -pos=9:1 -dont-print-response -vfs-files=/target_file2.swift=@%S/../Inputs/vfs/other_file_in_target.swift,/CModule/module.modulemap=%S/../Inputs/vfs/CModule/module.modulemap,/CModule/CModule.h=%S/../Inputs/vfs/CModule/CModule.h,/SwiftModule/SwiftModule.swiftmodule=%t/SwiftModule.swiftmodule %s -pass-as-sourcetext -- %s /target_file2.swift -I /CModule -I /SwiftModule -target %target-triple \