feature: add constant declarations #423
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this is implemented as `is_const` field in `VariableDecl`, so constants are technically variables that cannot be reassigned.
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i just checked,
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The reason why I never introduces 
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When we start to support |
i'd rather have it defined as a function that always returns the same literal |
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The idea of a function that returns always the same value I think that is the best and assure that can't change. |
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I'd say go with the @Ph0enixKM idea, since functions have an additional performance penalty. It doesn't matter that a constant is technically a regular variable, so long as it is translated from an Amber constant, thus is proven to be impossible to modify. |
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I think that we can move on with a function that return always the same value so we can assure the best compatibility. |
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In order to resolve this discussion I've created the following poll: #493 |
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@Ph0enixKM im confused, though. afaik we don't support |
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I think that we eventually will support |
| @@ -36,6 +36,10 @@ impl SyntaxModule<ParserMetadata> for VariableSet { | |||
| let variable = handle_variable_reference(meta, tok.clone(), &self.name)?; | |||
| self.global_id = variable.global_id; | |||
| self.is_ref = variable.is_ref; | |||
| // Check for constant reassignment | |||
| if variable.is_const { | |||
| return error!(meta, tok, format!("Cannot reassign constant")) | |||
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Can this error message say a bit more about what variable cannot be reassigned?
| @@ -68,7 +69,8 @@ pub enum StatementType { | |||
| Mv(Mv), | |||
| CommandModifier(CommandModifier), | |||
| Comment(Comment), | |||
| CommentDoc(CommentDoc) | |||
| CommentDoc(CommentDoc), | |||
| ConstInit(ConstInit) | |||
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Would be helpful to get in the habit of adding a comma to the last item of multi-line Rust lists (applies to struct fields, function definition parameters, function call arguments, vec![] initialisations, etc) when you're making changes anyway. This it makes subsequent pull requests (marginally) nicer. If this had been done to CommentDoc(CommentDoc) when that was added, you would have one changed line here, not two.
| let global_id = self.is_global_scope().then(|| self.gen_var_id()); | ||
| let scope = self.context.scopes.last_mut().unwrap(); | ||
| scope.add_var(VariableDecl { | ||
| name: name.to_string(), | ||
| kind, | ||
| global_id, | ||
| is_ref: false | ||
| is_ref: false, | ||
| is_const |
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Two more places to add trailing commas, in add_var() and add_param().
| } | ||
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| impl SyntaxModule<ParserMetadata> for ConstInit { | ||
| syntax_name!("Constant Initialization"); |
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The equivalent line in init.rs is:
syntax_name!("Variable Initialize");
Consider changing one or the other to match.
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Approved subject to suggestions from both myself and @Ph0enixKM.
i've added support for the
const X = Yexpression itself. it will resolve todeclare -r X=Y, for both local and global variables, sincedeclare -ris the same for locals as welli also set
argsinmain(args)to be constant. function parameters are never constant.i don't know which is the minimal bash version for
declare -r