Feat(compiler-base): add error message.

[zong-zhe]

1. Does this PR affect any open issues?(Y/N) and add issue references (e.g. "fix #123", "re #123".):

• N
• Y

issue #115

2. What is the scope of this PR (e.g. component or file name):

compiler_base/error_message.rs

3. Provide a description of the PR(e.g. more details, effects, motivations or doc link):

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Other

add ErrorMessage to define the message displayed in diagnostics.
add TemplateLoader to load text template file ("*.ftl").

4. Are there any breaking changes?(Y/N) and describe the breaking changes(e.g. more details, motivations or doc link):

• N
• Y

5. Are there test cases for these changes?(Y/N) select and add more details, references or doc links:

• Unit test
• Integration test
• Benchmark (add benchmark stats below)
• Manual test (add detailed scripts or steps below)
• Other

add unit test in compiler_base/tests.rs

6. Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

None

[github-actions]

CLA Assistant Lite bot All contributors have signed the CLA ✍️ ✅

[zong-zhe]

I have read the CLA Document and I hereby sign the CLA

[coveralls]

Pull Request Test Coverage Report for Build 2933389271

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 587 unchanged lines in 12 files lost coverage.
• Overall coverage decreased (-0.4%) to 59.515%

---

Files with Coverage Reduction	New Missed Lines	%
kclvm/runtime/src/_kclvm.rs	3	25.0%
kclvm/runtime/src/stdlib/plugin.rs	3	0%
kclvm/runtime/src/_kclvm_addr.rs	7	0%
kclvm/span/src/symbol.rs	10	60.0%
kclvm/parser/src/parser/expr.rs	13	81.58%
kclvm/runtime/src/api/utils.rs	26	18.33%
kclvm/runtime/src/api/kclvm.rs	33	46.88%
kclvm/runtime/src/types/api.rs	40	0%
kclvm/runtime/src/value/val_plan.rs	50	0%
kclvm/compiler/src/codegen/llvm/node.rs	60	89.62%

Totals
Change from base Build 2908762349:	-0.4%
Covered Lines:	21948
Relevant Lines:	36878

---

💛 - Coveralls

[Peefy]

Three important things:

1. It is recommended to use anyhow::Result as a function return instead of .unwrap_or_else(|| bug!("error message")) Because it's not actually an internal compiler error but a user error.
2. Whether it is a high-level or medium-level API, try to keep the interface as simple as possible, such as importing only one file and using one structure.
3. Try the once_cell crate to init TempateMessageLoader.

[Peefy]

LGTM

[ldxdl]

LGM