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dcast.d: Improve pointer conversion error messages (#21221)

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Abhay Pratap 2025-04-15 15:33:44 +05:30 • committed by GitHub
parent f4ca164257
commit 513293b0d8
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3 changed files with 47 additions and 9 deletions
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23
compiler/src/dmd/dcast.d
View file

@ -161,8 +161,27 @@ Expression implicitCastTo(Expression e, Scope* sc, Type t)
return ErrorExp.get(); return ErrorExp.get();
} }
error(e.loc, "cannot implicitly convert expression `%s` of type `%s` to `%s`", // Special case for pointer conversions
e.toErrMsg(), ts[0], ts[1]); if (e.type.toBasetype().ty == Tpointer && t.toBasetype().ty == Tpointer)
{
Type fromPointee = e.type.nextOf();
Type toPointee = t.nextOf();
// Const -> mutable conversion (disallowed)
if (fromPointee.isConst() && !toPointee.isConst())
{
error(e.loc, "cannot implicitly convert `%s` to `%s`", e.type.toChars(), t.toChars());
errorSupplemental(e.loc, "Note: Converting const to mutable requires an explicit cast (`cast(int*)`).");
return ErrorExp.get();
}
// Incompatible pointee types (e.g., int* -> float* )
else if (fromPointee.toBasetype().ty != toPointee.toBasetype().ty)
{
error(e.loc, "cannot implicitly convert `%s` to `%s`", e.type.toChars(), t.toChars());
errorSupplemental(e.loc, "Note: Pointer types point to different base types (`%s` vs `%s`)", fromPointee.toChars(), toPointee.toChars());
return ErrorExp.get();
}
}
error(e.loc, "cannot implicitly convert expression `%s` of type `%s` to `%s`", e.toErrMsg(), ts[0], ts[1]);
} }
} }
return ErrorExp.get(); return ErrorExp.get();

17
compiler/test/fail_compilation/diag_ptr_conversion.d Normal file
View file

@ -0,0 +1,17 @@
/*
TEST_OUTPUT:
---
fail_compilation/diag_ptr_conversion.d(15): Error: cannot implicitly convert `const(int)*` to `int*`
fail_compilation/diag_ptr_conversion.d(15): Note: Converting const to mutable requires an explicit cast (`cast(int*)`).
fail_compilation/diag_ptr_conversion.d(16): Error: cannot implicitly convert `int*` to `float*`
fail_compilation/diag_ptr_conversion.d(16): Note: Pointer types point to different base types (`int` vs `float`)
---
*/
void testPointerConversions()
{
int* p;
const(int)* cp = p;
p = cp;
float* f = p;
}

16
compiler/test/fail_compilation/fail163.d
View file

@ -14,7 +14,8 @@ void test1()
/* /*
TEST_OUTPUT: TEST_OUTPUT:
--- ---
fail_compilation/fail163.d(24): Error: cannot implicitly convert expression `p` of type `const(int***)` to `const(int)***` fail_compilation/fail163.d(25): Error: cannot implicitly convert `const(int***)` to `const(int)***`
fail_compilation/fail163.d(25): Note: Converting const to mutable requires an explicit cast (`cast(int*)`).
--- ---
*/ */
void test2() void test2()
@ -27,7 +28,7 @@ void test2()
/* /*
TEST_OUTPUT: TEST_OUTPUT:
--- ---
fail_compilation/fail163.d(37): Error: cannot modify `const` expression `p` fail_compilation/fail163.d(38): Error: cannot modify `const` expression `p`
--- ---
*/ */
void test3() void test3()
@ -40,7 +41,7 @@ void test3()
/* /*
TEST_OUTPUT: TEST_OUTPUT:
--- ---
fail_compilation/fail163.d(50): Error: cannot implicitly convert expression `cp` of type `const(int)***[]` to `const(uint***)[]` fail_compilation/fail163.d(51): Error: cannot implicitly convert expression `cp` of type `const(int)***[]` to `const(uint***)[]`
--- ---
*/ */
void test4() void test4()
@ -53,7 +54,7 @@ void test4()
/* /*
TEST_OUTPUT: TEST_OUTPUT:
--- ---
fail_compilation/fail163.d(63): Error: cannot modify `const` expression `*p` fail_compilation/fail163.d(64): Error: cannot modify `const` expression `*p`
--- ---
*/ */
void test5() void test5()
@ -66,8 +67,8 @@ void test5()
/* /*
TEST_OUTPUT: TEST_OUTPUT:
--- ---
fail_compilation/fail163.d(76): Error: cannot implicitly convert expression `& x` of type `int*` to `immutable(int)*` fail_compilation/fail163.d(77): Error: cannot implicitly convert expression `& x` of type `int*` to `immutable(int)*`
fail_compilation/fail163.d(77): Error: cannot modify `immutable` expression `*p` fail_compilation/fail163.d(78): Error: cannot modify `immutable` expression `*p`
--- ---
*/ */
void test6() void test6()
@ -80,7 +81,8 @@ void test6()
/* /*
TEST_OUTPUT: TEST_OUTPUT:
--- ---
fail_compilation/fail163.d(89): Error: cannot implicitly convert expression `& x` of type `const(int)*` to `int*` fail_compilation/fail163.d(91): Error: cannot implicitly convert `const(int)*` to `int*`
fail_compilation/fail163.d(91): Note: Converting const to mutable requires an explicit cast (`cast(int*)`).
--- ---
*/ */
void test7() void test7()