Feature/unused vars (#1)
* TypeChecker - Adding new chapter `Variable referencing counting` * TypeChecker - Added missing method table - Added code usage * Markdown transform - Updated * Configuration - Documented `typecheck:warnUnusedVars` * Command line - Added compiler flags documentation * MK - Built * Command line - Formatting fixed * MK - Built
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@ -207,3 +207,68 @@ This is a sanity check, as if the type coercion failed then an exception
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would be thrown and the assertion would not be reached, however if the
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types were an exact match **or** if they were not but could be coerced
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as such then the two types should match.
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### Variable referencing counting
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Firstly let me make it clear that this has nothing to do with
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**runtime** reference counting but rather a simple mechanism used to
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maintain a count or *number of* references to variables after their
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declaration.
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Below is a method table of the methods of concern:
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| Method | Description | Return |
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|------------------------|-----------------------------------------------------------------------------------------------|--------------|
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| `touch(Variable)` | Increments the count by 1 for the given variable, creates a mapping if one does not yet exist | `void` |
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| `getUnusedVariables()` | Returns an array of all `Variable`s which have a reference count above `1` | `Variable[]` |
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This aids us in implementing a single feature *unused variable
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detection*. It’s rather simple, reference counts are incremented by
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using a `touch(Variable)` method defined in the `TypeChecker` and this
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is called whilst doing dependency generation in the dependency
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generator.
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The first time a variable is encountered, such as even its declaration,
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we will then `touch(...)`-it. At the end of type checking we then call
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the `getUnusedVariables()` method which returns a list of the undeclared
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variables. These are variables with a reference count higher than `1`.
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We then print these out so the user can see which are unused.
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#### Usage
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Example usage below shows us `touch`-ing a variable when we process them
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in expressions such as a `VariableExpression` in the dependency module:
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``` d
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...
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/* Get the entity as a Variable */
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Variable variable = cast(Variable)namedEntity;
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/* Variable reference count must increase */
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tc.touch(variable);
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...
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```
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We then, after typechecking, run the following in the type checker
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module’s `doPostChecks()` method:
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``` d
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/**
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* Find the variables which were declared but never used
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*/
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if(this.config.hasConfig("typecheck:warnUnusedVars") & this.config.getConfig("typecheck:warnUnusedVars").getBoolean())
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{
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Variable[] unusedVariables = getUnusedVariables();
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gprintln("There are "~to!(string)(unusedVariables.length)~" unused variables");
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if(unusedVariables.length)
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{
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foreach(Variable unusedVariable; unusedVariables)
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{
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// TODO: Get a nicer name, full path-based
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gprintln("Variable '"~to!(string)(unusedVariable.getName())~"' is declared but never");
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}
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}
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}
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```
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@ -62,7 +62,7 @@ before adding them here
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### Statements
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Statements are inevitably the building blocks of a program and make use
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of all the former defined sections of the grammar and more of themsleves
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of all the former defined sections of the grammar and more of themselves
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in some cases as well.
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module ::= "module", ident, ";", {decl, ";"};
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@ -1,7 +1,7 @@
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## Configuration
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The T compiler can have various variables tweaked to control the
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bahviour of the compiler
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behavior of the compiler
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### `types`
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@ -9,10 +9,10 @@ Anything regarding the type system (this includes the type checker and
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the meta processor).
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1. `types:max_width`
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- This entry holds an integrak value
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- This entry holds an integral value
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- This sets the maximum bit-width of a machine (in bytes)
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- This can either be `1`, `2`, `4` or `8`
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- It affects how alises such as `size_t` and `ssize_t` behave in
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- It affects how aliases such as `size_t` and `ssize_t` behave in
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terms of what the resolve to
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### `dgen`
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@ -57,3 +57,13 @@ This controls aspects of the `CodeEmitter` API, meaning irrespective of
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which emitter (such as `dgen`) is used.
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TODO: Move `dgen_emit_entrypoint_test` and `dgen:pretty_code` here.
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### `typecheck`
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This controls the aspects of the `TypeChecker`.
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1. `typecheck:warnUnusedVars`
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- If this is set to `true` then at the end of the typechecking
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process a scan for all variables will be done and any variable
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that is unused will be printed out
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- Default: `true`
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@ -0,0 +1,12 @@
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## Command-line
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This documents the full set of available command-line flags one can use.
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### `--unusedVars <boolean>`
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- **What**: Allows one to toggle whether or not warnings about unused
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variables should be printed out or not.
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- **Where**: Can be used with the `typecheck`, `emit` and `compile`
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commands.
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- **How**: This toggles the compiler configuration entry
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`typecheck:warnUnusedVars`
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@ -285,4 +285,56 @@ assert(isSameType(
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); // Sanity check
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```
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This is a sanity check, as if the type coercion failed then an exception would be thrown and the assertion would not be reached, however if the types were an exact match **or** if they were not but could be coerced as such then the two types should match.
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This is a sanity check, as if the type coercion failed then an exception would be thrown and the assertion would not be reached, however if the types were an exact match **or** if they were not but could be coerced as such then the two types should match.
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### Variable referencing counting
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Firstly let me make it clear that this has nothing to do with **runtime** reference counting but rather a simple mechanism used to maintain a count or _number of_ references to variables after their declaration.
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Below is a method table of the methods of concern:
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| Method | Description | Return |
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|--------|-------------|--------|
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| `touch(Variable)` | Increments the count by 1 for the given variable, creates a mapping if one does not yet exist | `void` |
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| `getUnusedVariables()` | Returns an array of all `Variable`s which have a reference count above `1` | `Variable[]` |
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This aids us in implementing a single feature _unused variable detection_. It's rather simple, reference counts are incremented by using a `touch(Variable)` method defined in the `TypeChecker` and this is called whilst doing dependency generation in the dependency generator.
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The first time a variable is encountered, such as even its declaration, we will then `touch(...)`-it. At the end of type checking we then call the `getUnusedVariables()` method which returns a list of the undeclared variables. These are variables with a reference count higher than `1`. We then print these out so the user can see which are unused.
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#### Usage
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Example usage below shows us `touch`-ing a variable when we process them in expressions such as a `VariableExpression` in the dependency module:
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```{.d .numberLines}
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...
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/* Get the entity as a Variable */
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Variable variable = cast(Variable)namedEntity;
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/* Variable reference count must increase */
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tc.touch(variable);
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...
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```
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We then, after typechecking, run the following in the type checker module's `doPostChecks()` method:
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```{.d .numberLines}
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/**
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* Find the variables which were declared but never used
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*/
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if(this.config.hasConfig("typecheck:warnUnusedVars") & this.config.getConfig("typecheck:warnUnusedVars").getBoolean())
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{
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Variable[] unusedVariables = getUnusedVariables();
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gprintln("There are "~to!(string)(unusedVariables.length)~" unused variables");
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if(unusedVariables.length)
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{
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foreach(Variable unusedVariable; unusedVariables)
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{
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// TODO: Get a nicer name, full path-based
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gprintln("Variable '"~to!(string)(unusedVariable.getName())~"' is declared but never");
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}
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}
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}
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```
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@ -47,3 +47,10 @@ This controls aspects of the `CodeEmitter` API, meaning irrespective of which em
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TODO: Move `dgen_emit_entrypoint_test` and `dgen:pretty_code` here.
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### `typecheck`
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This controls the aspects of the `TypeChecker`.
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1. `typecheck:warnUnusedVars`
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* If this is set to `true` then at the end of the typechecking process a scan for all variables will be done and any variable that is unused will be printed out
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* Default: `true`
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@ -0,0 +1,10 @@
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## Command-line
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This documents the full set of available command-line flags one can use.
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### `--unusedVars <boolean>`
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* **What**: Allows one to toggle whether or not warnings about unused variables should be printed out or not.
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* **Where**: Can be used with the `typecheck`, `emit` and `compile` commands.
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* **How**: This toggles the compiler configuration entry `typecheck:warnUnusedVars`
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