[clang] [clang-tools-extra] [lldb] [clang] implement CWG1980 and CWG2064: instantiation-dependency improvements (PR #190495)

[Oliver Hunt via cfe-commits]

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@@ -2966,8 +2991,27 @@ class ASTContext : public RefCountedBase<ASTContext> {
     return getCanonicalType(T1) == getCanonicalType(T2);
   }
 
+  QualType getCanonicalType(QualType QT, CanonicalizationKind Kind) const;
+  QualType getCanonicalType(QualType QT, CanonicalizationKind Kind,
+                            bool &AnyNonCanonical) const {
+    QualType R = getCanonicalType(QT, Kind);
+    AnyNonCanonical |= !R.isCanonical();
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ojhunt wrote:

this is likely a dumb question, in what cases does `getCanonicalType(...)` return a non-canonical type?

https://github.com/llvm/llvm-project/pull/190495