[-Wunsafe-buffer-usage] Preserve array element type spelling in std::array fixits

In other words - don't use the type that the source code gets expanded
to in the AST as there's very likely a reason why it is represented via
a typedef or macro in the sourcode.

Author: jkorous-apple

clang/lib/Analysis/UnsafeBufferUsage.cpp

@@ -12,6 +12,8 @@
 #include "clang/AST/RecursiveASTVisitor.h"
 #include "clang/AST/StmtVisitor.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Basic/CharInfo.h"
+#include "clang/Basic/SourceLocation.h"
 #include "clang/Lex/Lexer.h"
 #include "clang/Lex/Preprocessor.h"
 #include "llvm/ADT/APSInt.h"
@@ -2492,8 +2494,25 @@ static FixItList fixVarDeclWithArray(const VarDecl *D, const ASTContext &Ctx,
       return {};
     }
 
+    const SourceLocation IdentifierLoc = getVarDeclIdentifierLoc(D);
+
+    // Get the spelling of the element type as written in the source file (including macros, etc.).
+    auto MaybeElemTypeTxt = getRangeText({D->getBeginLoc(), IdentifierLoc}, Ctx.getSourceManager(), Ctx.getLangOpts());
+    if (!MaybeElemTypeTxt)
+      return {};
+    std::string ElemTypeTxt = MaybeElemTypeTxt->str();
+    // Trim whitespace from the type spelling.
+    unsigned TrailingWhitespace = 0;
+    for (auto It = ElemTypeTxt.rbegin(); It < ElemTypeTxt.rend(); ++It) {
+      if (!isWhitespace(*It))
+        break;
+      ++TrailingWhitespace;
+    }
+    if (TrailingWhitespace > 0)
+      ElemTypeTxt.erase(ElemTypeTxt.length() - TrailingWhitespace);
+
     // Find the '[' token.
-    std::optional<Token> NextTok = Lexer::findNextToken(getVarDeclIdentifierLoc(D), Ctx.getSourceManager(), Ctx.getLangOpts());
+    std::optional<Token> NextTok = Lexer::findNextToken(IdentifierLoc, Ctx.getSourceManager(), Ctx.getLangOpts());
     while (NextTok && !NextTok->is(tok::l_square))
       NextTok = Lexer::findNextToken(NextTok->getLocation(), Ctx.getSourceManager(), Ctx.getLangOpts());
     if (!NextTok)
@@ -2517,7 +2536,7 @@ static FixItList fixVarDeclWithArray(const VarDecl *D, const ASTContext &Ctx,
 
     SmallString<32> Replacement;
     raw_svector_ostream OS(Replacement);
-    OS << "std::array<" << ArrayEltT.getAsString() << ", "
+    OS << "std::array<" << ElemTypeTxt << ", "
        << ArraySizeTxt << "> " << IdentText->str();
 
     FixIts.push_back(FixItHint::CreateReplacement(

clang/test/SemaCXX/warn-unsafe-buffer-usage-fixits-local-var-array.cpp

@@ -18,7 +18,7 @@ void weird_whitespace_in_declaration(unsigned idx) {
 
 void weird_comments_in_declaration(unsigned idx) {
   int   /* [ ] */   buffer_w  /* [ ] */ [ /* [ ] */ 10 /* [ ] */ ] ;
-// CHECK: fix-it:"{{.*}}":{[[@LINE-1]]:3-[[@LINE-1]]:67}:"std::array<int,  /* [ ] */ 10 /* [ ] */ > buffer_w"
+// CHECK: fix-it:"{{.*}}":{[[@LINE-1]]:3-[[@LINE-1]]:67}:"std::array<int   /* [ ] */,  /* [ ] */ 10 /* [ ] */ > buffer_w"
   buffer_w[idx] = 0;
 }
 
@@ -65,6 +65,21 @@ void local_array_in_template(unsigned idx) {
 // Instantiate the template function to force its analysis.
 template void local_array_in_template<int>(unsigned); // FIXME: expected note {{in instantiation of}}
 
+typedef unsigned int uint;
+void typedef_as_elem_type(unsigned idx) {
+  uint buffer[10];
+// CHECK: fix-it:"{{.*}}":{[[@LINE-1]]:3-[[@LINE-1]]:18}:"std::array<uint, 10> buffer"
+  buffer[idx] = 0;
+}
+
+void macro_as_elem_type(unsigned idx) {
+#define MY_INT int
+  MY_INT buffer[10];
+// FIXME: implement support
+  buffer[idx] = 0;
+#undef MY_INT
+}
+
 void macro_as_identifier(unsigned idx) {
 #define MY_BUFFER buffer
   int MY_BUFFER[10];
@@ -76,7 +91,7 @@ void macro_as_identifier(unsigned idx) {
 void macro_as_size(unsigned idx) {
 #define MY_TEN 10
   int buffer[MY_TEN];
-// CHECK-NOT: fix-it:"{{.*}}":{[[@LINE-1]]
+// CHECK: fix-it:"{{.*}}":{[[@LINE-1]]:3-[[@LINE-1]]:21}:"std::array<int, MY_TEN> buffer"
   buffer[idx] = 0;
 #undef MY_TEN
 }