Improve error reporting on invalid code

[hholst80]

Describe the bug

The following invalid code gives poor error reports:

fn main() {
	dummy := map[string][bool] // invalid syntax should be map[string]bool{}
	for i := 0; i < 10; i++ {
	}
}

Reproduction Steps

[I] root@trump ~ [1]
# v fmt -w e.v
e.v:2:24: error: maps can only have a single key
    1 | fn main() {
    2 |   dummy := map[string][bool]
      |                        ~~~~
    3 |   for i := 0; i < 10; i++ {
    4 |   }

Internal vfmt error while formatting file: e.v.
Encountered a total of: 1 errors.
[I] root@trump ~ [1]
# v e.v
e.v:3:15: error: expression evaluated but not used
    1 | fn main() {
    2 |   dummy := map[string][bool]
    3 |   for i := 0; i < 10; i++ {
      |               ~~~~~~
    4 |   }
    5 | }

Expected Behavior

I would like to see "syntax error" or something more non-spurious.
The compiler should not point out the for-loop below for sure.

Current Behavior

See above.

Possible Solution

No response

Additional Information/Context

No response

V version

V 0.4.4 cf7dcfe

Environment details (OS name and version, etc.)

V full version: V 0.4.4 cf7dcfe
OS: linux, "Artix Linux"
Processor: 4 cpus, 64bit, little endian, Intel(R) Core(TM) i7-6600U CPU @ 2.60GHz

getwd: /home/root
vexe: /home/root/Apps/v/v
vexe mtime: 2024-02-27 14:30:38

vroot: OK, value: /home/root/Apps/v
VMODULES: OK, value: /home/root/.vmodules
VTMP: OK, value: /tmp/v_0

Git version: git version 2.43.1
Git vroot status: weekly.2024.10-3-ga867ed6a (57 commit(s) behind V master)
.git/config present: true

CC version: cc (GCC) 13.2.1 20230801
thirdparty/tcc status: thirdparty-linux-amd64 40e5cbb5

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