Sema: typo correct both sides of binary expression

[compnerd]

Summary

When parsing a ternary expression, we would parse the middle and the last
components of the expression. If there was a typo in both, we would only
run the typo correction once. Normally, this would be fine, but, when Sema
would be destructed in an Asserts build, we would assert that a delayed typo was
not handled. This was caused by the fact that the RHS would evaluate as valid
as a TypoExpr would be returned via the ExprResult, and invalid simply ensures
that an expression is present. Peek into the result and perform the handling
that we would reserve for the invalid type.

Resolves PR265598.

[rtrieu]

While this change does add the intended error messages, it won't produce a correct a typo-corrected AST. For instance:

void run(int sss) {
 sss = ssss ? ssss : ssss;
}

Will produce an empty function body:

`-FunctionDecl 0x7082ef0 <typo2.cc:1:1, line:3:1> line:1:6 run 'void (int)'
  |-ParmVarDecl 0x7082e30 <col:10, col:14> col:14 used sss 'int'
  `-CompoundStmt 0x70830f8 <col:19, line:3:1>

While the old code would make an AST for the body:

`-FunctionDecl 0x59c0790 <typo2.cc:1:1, line:3:1> line:1:6 run 'void (int)'
  |-ParmVarDecl 0x59c06d0 <col:10, col:14> col:14 used sss 'int'
  `-CompoundStmt 0x59c0a90 <col:19, line:3:1>
    `-BinaryOperator 0x59c0a68 <line:2:2, col:22> 'int' lvalue '='
      |-DeclRefExpr 0x59c0880 <col:2> 'int' lvalue ParmVar 0x59c06d0 'sss' 'int'
      `-ImplicitCastExpr 0x59c0a50 <col:8, col:22> 'int' <LValueToRValue>
        `-ConditionalOperator 0x59c0a20 <col:8, col:22> 'int' lvalue
          |-ImplicitCastExpr 0x59c0a08 <col:8> '_Bool' <IntegralToBoolean>
          | `-ImplicitCastExpr 0x59c09f0 <col:8> 'int' <LValueToRValue>
          |   `-DeclRefExpr 0x59c0978 <col:8> 'int' lvalue ParmVar 0x59c06d0 'sss' 'int'
          |-DeclRefExpr 0x59c09a0 <col:15> 'int' lvalue ParmVar 0x59c06d0 'sss' 'int'
          `-DeclRefExpr 0x59c09c8 <col:22> 'int' lvalue ParmVar 0x59c06d0 'sss' 'int'

lib/Parse/ParseExpr.cpp

     else
       RHS = ParseCastExpression(false);
 
-    if (RHS.isInvalid()) {
+    if (RHS.isInvalid() || isa<TypoExpr>(RHS.get())) {
       // FIXME: Errors generated by the delayed typo correction should be
       // printed before errors from parsing the RHS, not after.
       Actions.CorrectDelayedTyposInExpr(LHS);

test/SemaCXX/typo-correction-cxx11.cpp

 namespace PR23140 {
 auto lneed = gned.*[] {};  // expected-error-re {{use of undeclared identifier 'gned'{{$}}}}
 
-void test(int aaa, int bbb, int thisvar) {  // expected-note {{'thisvar' declared here}}
-  int thatval = aaa * (bbb + thatvar);  // expected-error {{use of undeclared identifier 'thatvar'; did you mean 'thisvar'?}}
+void test(int aaa, int bbb, int thisvar) {
+  // expected-note@-1 {{'thisvar' declared here}}
+  int thatval = aaa * (bbb + thatvar);
+  // expected-error@-1 {{use of undeclared identifier 'thatvar'; did you mean 'thatval'?}}
+  // expected-note@-2 {{'thatval' declared here}}
+  int thatval2 = aaa * (bbb + thisval);
+  // expected-error@-1 {{use of undeclared identifier 'thisval'; did you mean 'thisvar'?}}
 }
 }
 

test/SemaCXX/typo-correction-delayed.cpp

 // expected-error-re@-1 {{use of undeclared identifier 'N'{{$}}}}
 }
 
+namespace PR26598 {
+int main() {
+  (((str) ? str : str))
+  // expected-error@-1 {{use of undeclared identifier 'str'}}
+  // expected-error@-2 {{use of undeclared identifier 'str'}}
+  // expected-error@-3 {{use of undeclared identifier 'str'}}
+}
+}
+
 // PR 23285. This test must be at the end of the file to avoid additional,
 // unwanted diagnostics.
 // expected-error-re@+2 {{use of undeclared identifier 'uintmax_t'{{$}}}}
 // expected-error@+1 {{expected ';' after top level declarator}}
 unsigned int a = 0(uintmax_t
+

test/SemaObjC/provisional-ivar-lookup.m

 // rdar:// 8565343
 @interface Foo  {
 @private
-    int _foo;
+    int _foo; // expected-note {{'_foo' declared here}}
     int _foo2;
 }
 @property (readwrite, nonatomic) int foo, foo1, foo2, foo3;

 @synthesize foo1;
 
 - (void)setFoo:(int)value {
-    _foo = foo; // expected-error {{use of undeclared identifier 'foo'}}
+    _foo = foo; // expected-error {{use of undeclared identifier 'foo'; did you mean '_foo'}}
 }
 
 - (void)setFoo1:(int)value {