Direct and camel-cased concatenation fixits for repeated identifiers in function declarations

Additional QoI to also provide a fix-it to concatenate in camel-case.

rdar://problem/25761940

Author: bitjammer

include/swift/AST/DiagnosticsParse.def

@@ -663,6 +663,10 @@ ERROR(keyword_cant_be_identifier,none,
       "keyword '%0' cannot be used as an identifier here", (StringRef))
 ERROR(repeated_identifier,none,
       "found an unexpected second identifier in %0 declaration; is there an accidental break?", (StringRef))
+NOTE(join_identifiers,none,
+     "join the identifiers together", ())
+NOTE(join_identifiers_camel_case,none,
+     "join the identifiers together with camel-case", ())
 NOTE(backticks_to_escape,none,
      "if this name is unavoidable, use backticks to escape it", ())
 ERROR(expected_rparen_tuple_pattern_list,none,

lib/Parse/ParseDecl.cpp

@@ -25,6 +25,7 @@
 #include "swift/AST/ParameterList.h"
 #include "swift/Basic/Defer.h"
 #include "swift/Basic/Fallthrough.h"
+#include "swift/Basic/StringExtras.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/SaveAndRestore.h"
@@ -4463,9 +4464,27 @@ Parser::parseDeclFunc(SourceLoc StaticLoc, StaticSpellingKind StaticSpelling,
     // identifier, it might've been a single identifier that got broken by a
     // space or newline accidentally.
     if (Tok.isIdentifierOrUnderscore() && SimpleName.str().back() != '<') {
-      diagnose(Tok.getLoc(), diag::repeated_identifier, "function")
-        .fixItReplace(SourceRange(NameLoc, Tok.getLoc()),
-                      NameTok.getText().str() + Tok.getText().str());
+      diagnose(Tok.getLoc(), diag::repeated_identifier, "function");
+
+      SourceRange DoubleIdentifierRange(NameLoc, Tok.getLoc());
+
+      // Provide two fix-its: a direct concatentation of the two identifiers
+      // and a camel-cased version.
+
+      auto DirectConcatenation = NameTok.getText().str() + Tok.getText().str();
+
+      diagnose(Tok.getLoc(), diag::join_identifiers)
+        .fixItReplace(DoubleIdentifierRange, DirectConcatenation);
+
+      SmallString<8> CapitalizedScratch;
+      auto Capitalized = camel_case::toSentencecase(Tok.getText(),
+                                                    CapitalizedScratch);
+      auto CamelCaseConcatenation = NameTok.getText().str() + Capitalized.str();
+
+      if (DirectConcatenation != CamelCaseConcatenation)
+        diagnose(Tok.getLoc(), diag::join_identifiers_camel_case)
+          .fixItReplace(DoubleIdentifierRange, CamelCaseConcatenation);
+
       consumeToken();
     }
   }

test/Parse/invalid.swift

@@ -98,12 +98,22 @@ let for = 2
 // expected-error @-1 {{keyword 'for' cannot be used as an identifier here}}
 // expected-note @-2 {{if this name is unavoidable, use backticks to escape it}} {{5-8=`for`}}
 
-func dog cow() {} // expected-error {{found an unexpected second identifier in function declaration; is there an accidental break?}} {{6-13=dogcow}}
-func friend ship<T>(x: T) {} // expected-error {{found an unexpected second identifier in function declaration; is there an accidental break?}} {{6-17=friendship}}
+func dog cow() {} // expected-error {{found an unexpected second identifier in function declaration; is there an accidental break?}}
+// expected-note@-1 {{join the identifiers together}} {{6-13=dogcow}}
+// expected-note@-2 {{join the identifiers together with camel-case}} {{6-13=dogCow}}
+func cat Mouse() {} // expected-error {{found an unexpected second identifier in function declaration; is there an accidental break?}}
+// expected-note@-1 {{join the identifiers together}} {{6-15=catMouse}}
+func friend ship<T>(x: T) {} // expected-error {{found an unexpected second identifier in function declaration; is there an accidental break?}}
+// expected-note@-1 {{join the identifiers together}} {{6-17=friendship}}
+// expected-note@-2 {{join the identifiers together with camel-case}} {{6-17=friendShip}}
 func were
-wolf() {} // expected-error {{found an unexpected second identifier in function declaration; is there an accidental break?}} {{6-5=werewolf}}
+wolf() {} // expected-error {{found an unexpected second identifier in function declaration; is there an accidental break?}}
+// expected-note@-1 {{join the identifiers together}} {{6-5=werewolf}}
+// expected-note@-2 {{join the identifiers together with camel-case}} {{6-5=wereWolf}}
 func hammer
-leavings<T>(x: T) {} // expected-error {{found an unexpected second identifier in function declaration; is there an accidental break?}} {{6-9=hammerleavings}}
+leavings<T>(x: T) {} // expected-error {{found an unexpected second identifier in function declaration; is there an accidental break?}}
+// expected-note@-1 {{join the identifiers together}} {{6-9=hammerleavings}}
+// expected-note@-2 {{join the identifiers together with camel-case}} {{6-9=hammerLeavings}}
 
 prefix operator % {}
 prefix func %<T>(x: T) -> T { return x } // No error expected - the < is considered an identifier but is peeled off by the parser.