Bug 6638 – Suggestions/error messages for misuses of for/foreach

Languages and compilers copy each other all the time. This is a low-priority diagnostic enhancement request inspired by Rust compiler: https://github.com/graydon/rust/wiki/Error-reporting > Use of for where for each was meant. > > for (v in foo.iter()) // suggest "for each" This is wrong D code (in my code the mistakes #5 and #7 are common enough): void main() { for (i; 0 .. 10) {} // #1 int[5] a; for (x; a) {} // #2 foreach (int = 0; i < 10; i++) {} // #3 foreach (i, 0 .. 10) {} // #4 foreach (i, x, a) {} // #5 foreach (i; x, a) {} // #6 foreach (i; x; a) {} // #7 } DMD 2.055 gives: test.d(2): found '..' when expecting ';' following for condition test.d(4): found ')' when expecting ';' following for condition test.d(5): found 'foreach' when expecting ')' test.d(5): found '=' when expecting '.' following int test.d(5): found '0' when expecting identifier following 'int.' test.d(5): found ';' when expecting ')' test.d(5): found 'i' when expecting ';' following statement test.d(5): found '<' instead of statement test.d(5): found ')' when expecting ';' following statement test.d(6): basic type expected, not 0 test.d(6): no identifier for declarator int test.d(6): found '0' when expecting ';' test.d(6): expression expected, not '..' test.d(6): found '10' when expecting ')' test.d(6): found ')' instead of statement test.d(7): Declaration expected, not 'foreach' test.d(8): no identifier for declarator x test.d(8): semicolon expected, not ')' test.d(8): Declaration expected, not ')' test.d(9): no identifier for declarator x test.d(9): no identifier for declarator a In some (or all) such 7 situations the D compiler can generate specific better error messages, with a suggestion.

The Error message is still bad in 2020 but ultimately this would mean adding a bunch of new logic to the parser to fix something pretty obvious (to be blunt)