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fix RFC #341: dot-like operators are now parsed with same precedence as . (#18711)

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* fix RFC #341: dot-like operators are now parsed with same precedence as `.`

* fixup

* [skip ci] address comment in changelog

* address comment

* update grammmar

* add manual entry

* fixup

* -d:nimPreviewDotLikeOps

* address comment to unblock PR: move nimPreviewDotLikeOps out of config/config.nims
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Timothee Cour 2021-08-24 21:50:40 -07:00 • committed by GitHub
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7 changed files with 74 additions and 5 deletions
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2
doc/grammar.txt
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@ -29,6 +29,7 @@ exprList = expr ^+ comma
exprColonEqExprList = exprColonEqExpr (comma exprColonEqExpr)* (comma)?
dotExpr = expr '.' optInd (symbol | '[:' exprList ']')
explicitGenericInstantiation = '[:' exprList ']' ( '(' exprColonEqExpr ')' )?
dotLikeExpr = expr DOTLIKEOP optInd symbol
qualifiedIdent = symbol ('.' optInd symbol)?
setOrTableConstr = '{' ((exprColonEqExpr comma)* | ':' ) '}'
castExpr = 'cast' ('[' optInd typeDesc optPar ']' '(' optInd expr optPar ')') /
@ -56,6 +57,7 @@ tupleConstr = '(' optInd (exprColonEqExpr comma?)* optPar ')'
arrayConstr = '[' optInd (exprColonEqExpr comma?)* optPar ']'
primarySuffix = '(' (exprColonEqExpr comma?)* ')'
| '.' optInd symbol generalizedLit?
| DOTLIKEOP optInd symbol generalizedLit?
| '[' optInd exprColonEqExprList optPar ']'
| '{' optInd exprColonEqExprList optPar '}'
| &( '`'|IDENT|literal|'cast'|'addr'|'type') expr # command syntax

9
doc/manual.rst
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@ -748,6 +748,7 @@ has the second-lowest precedence.
Otherwise, precedence is determined by the first character.
================ ======================================================= ================== ===============
Precedence level Operators First character Terminal symbol
================ ======================================================= ================== ===============
@ -783,6 +784,14 @@ of a call or whether it is parsed as a tuple constructor:
.. code-block:: nim
echo (1, 2) # pass the tuple (1, 2) to echo
Dot-like operators
------------------
Terminal symbol in the grammar: `DOTLIKEOP`.
Dot-like operators are operators starting with `.`, but not with `..`, for e.g. `.?`;
they have the same precedence as `.`, so that `a.?b.c` is parsed as `(a.?b).c` instead of `a.?(b.c)`.
Grammar
-------