[LifetimeSafety] False-negative for return of pointer to a parameter

[usx95]

https://godbolt.org/z/M5v3j6W84

#include <string>
#include <string_view>

std::string_view foo(std::string param) {
    std::string_view res = param;
    return res;
}

We do not see the expired loans for the param (no destructors)

==========================================
       Lifetime Analysis Facts:
==========================================
Function: foo
  Block B2:
  End of Block
  Block B1:
    Issue (0 (Path: param), ToOrigin: 0 (Expr: DeclRefExpr))
    OriginFlow (Dest: 1 (Expr: ImplicitCastExpr), Src: 0 (Expr: DeclRefExpr))
    OriginFlow (Dest: 2 (Expr: CXXMemberCallExpr), Src: 1 (Expr: ImplicitCastExpr))
    OriginFlow (Dest: 3 (Expr: ImplicitCastExpr), Src: 2 (Expr: CXXMemberCallExpr))
    OriginFlow (Dest: 4 (Decl: res), Src: 3 (Expr: ImplicitCastExpr))
    Use (4 (Decl: res), Read)
    OriginFlow (Dest: 5 (Expr: ImplicitCastExpr), Src: 4 (Decl: res))
    OriginFlow (Dest: 6 (Expr: CXXConstructExpr), Src: 5 (Expr: ImplicitCastExpr))
    OriginEscapes (6 (Expr: CXXConstructExpr))
  End of Block
  Block B0:
  End of Block

[llvmbot]

@llvm/issue-subscribers-clang-temporal-safety

Author: Utkarsh Saxena (usx95)

https://godbolt.org/z/M5v3j6W84 ```cpp #include <string> #include <string_view>

std::string_view foo(std::string param) {
std::string_view res = param;
return res;
}

We do not see the expired loans for the param (no destructors)

==========================================
Lifetime Analysis Facts:

Function: foo
Block B2:
End of Block
Block B1:
Issue (0 (Path: param), ToOrigin: 0 (Expr: DeclRefExpr))
OriginFlow (Dest: 1 (Expr: ImplicitCastExpr), Src: 0 (Expr: DeclRefExpr))
OriginFlow (Dest: 2 (Expr: CXXMemberCallExpr), Src: 1 (Expr: ImplicitCastExpr))
OriginFlow (Dest: 3 (Expr: ImplicitCastExpr), Src: 2 (Expr: CXXMemberCallExpr))
OriginFlow (Dest: 4 (Decl: res), Src: 3 (Expr: ImplicitCastExpr))
Use (4 (Decl: res), Read)
OriginFlow (Dest: 5 (Expr: ImplicitCastExpr), Src: 4 (Decl: res))
OriginFlow (Dest: 6 (Expr: CXXConstructExpr), Src: 5 (Expr: ImplicitCastExpr))
OriginEscapes (6 (Expr: CXXConstructExpr))
End of Block
Block B0:
End of Block

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