PChar of a one-character literal is its char code

p := PChar('x');
writeln(PtrUInt(p));   { pxx: 120; fpc 3.2.2: an address, p^ = 'x', p[1] = #0 }

The factor parser makes a one-character literal an AN_INT_LIT tagged tyChar, which is right in every ordinal context. The PChar cast (sentinel -2) lowers to its operand, so the code became the pointer. A named const KC = 'k' gives the same node with LastExprTk left at something other than tyChar, so the arm asks the node's kind as well.

fpc 3.2.2 on PChar(c) for a Char variable or a typed const Char: Illegal type conversion: "Char" to "PChar". pxx now gives the same refusal instead of making the char value an address.

PWideChar('w') is still behind PXX_WIDE_PAYLOAD. That refusal is unchanged, and chore-a-decide-whether-widestring-can-come-out-from-behind-pxx-wide-payload tracks it.

Tests

• test_pchar_of_a_one_character_literal: covers a literal, PAnsiChar, a named const, #65, a two-character control, a direct argument, ^ and [0]. The expected output is fpc 3.2.2's. It passes on six targets. The v451 compiler segfaults on it.
• test_pchar_of_a_char_variable_is_refused: the refusal row, with fpc's message.