error: expected at least one digit in exponent
  --> $DIR/issue-90728.rs:2:7
   |
LL |     a.5.2E+
   |       ^^^^^

error: unexpected token: `5.2E+`
  --> $DIR/issue-90728.rs:2:7
   |
LL |     a.5.2E+
   |       ^^^^^

error: expected one of `.`, `;`, `?`, `}`, or an operator, found `5.2E+`
  --> $DIR/issue-90728.rs:2:7
   |
LL |     a.5.2E+
   |       ^^^^^ expected one of `.`, `;`, `?`, `}`, or an operator

error: aborting due to 3 previous errors